Next Article in Journal
Research on the Effect of Argon–Nitrogen Ratio on the Mechanical Properties and Corrosion Behavior of CrN-Ag Self-Lubricating Coatings
Previous Article in Journal
Preparation of Tea Tree Essential Oil@Chitosan-Arabic Gum Microcapsules and Its Effect on the Properties of Waterborne Coatings
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Coatings
Volume 15
Issue 9
10.3390/coatings15091106
coatings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Microstructure Development of a Functionalized Multilayer Coating System of 316L Austenitic Steel on Grey Cast Iron Under Braking Force in a Corrosive Environment

by
Mohammad Masafi
1,*,†,
Achim Conzelmann
2,
Heinz Palkowski
1 and
Hadi Mozaffari-Jovein
2
1
Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld, Germany
2
Institute of Materials Science and Engineering Tuttlingen, Furtwangen University, Kronen-Str. 16, D-78532 Tuttlingen, Germany
*
Author to whom correspondence should be addressed.
†
Social media accounts author: https://de.linkedin.com/in/mohammad-masafi-7136607a (accessed on 18 September 2025).
Coatings 2025, 15(9), 1106; https://doi.org/10.3390/coatings15091106
Submission received: 28 August 2025 / Revised: 15 September 2025 / Accepted: 17 September 2025 / Published: 20 September 2025
(This article belongs to the Special Issue Novel Protective Coatings on Anti-Oxidation, Anti-Wear, and Corrosion Resistance Properties)
Browse Figures
Review Reports Versions Notes

Abstract

Grey cast iron brake discs with lamellar graphite (GJL) offer excellent strength and thermal conductivity but are prone to wear and dust emissions. To mitigate these issues, a multilayer coating was applied via Laser Metal Deposition (LMD), comprising a 316L stainless steel base layer and a WC-reinforced top layer. This study examines the microstructural evolution of the coatings under simulated thermomechanical and corrosive conditions using a brake shock corrosion test. Microstructural characterization was performed via Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), focusing on grain size, orientation, and texture before and after testing. EBSD analysis revealed significant grain coarsening, with sizes increasing from below 20 µm to 30–60 µm, and a shift toward <101> texture. Hardness measurements showed a reduction in the WC-reinforced layer from 478 HV to 432 HV and in the 316L base layer from 232 HV to 223 HV, confirming the influence of thermomechanical stress. SEM analysis revealed a transition from horizontal cracks—caused by residual stress during LMD—to vertical microcracks propagating from the substrate, activated by braking-induced loads. These findings provide insights into the microstructural response of LMD coatings under realistic service conditions and underscore the importance of grain boundary control in designing durable brake disc systems.

1. Introduction

The special properties of grey cast iron with flake graphite (GJL) include exceptional resonance damping behaviour and high thermal conductivity [1]. These properties make GJL an excellent material for numerous automotive applications, such as gearboxes, crankcases, brake discs and valves. Brake discs produced from GJL offer an optimum combination of strength and thermal conductivity. This is essential in meeting the high demands for braking performance and durability in the automotive industry [2]. However, cast iron’s inherent brittleness poses a significant challenge, particularly in areas subject to thermal and mechanical stress. Additionally, the dust emissions generated by cast iron are a growing concern due to their potential health risks and negative impact on air quality. Although this issue is well documented, the present study focuses on the microstructural development of multilayer coatings as a foundation for future improvements in emission-reducing surface technologies. Combining the favourable properties of GJL brake discs with a wear-resistant coating can significantly reduce particulate emissions. One promising approach for applying such coatings is the Laser Metal Deposition (LMD) process [3].
LMD is a coating manufacturing process where 3D parts are coated layer by directly melting and depositing the material on the substrate [4]. This technique can be further classified into Wire Laser Metal Deposition and Powder Laser Metal Deposition based on the type of material feedstock used [5,6]. LMD has gained significant attention in recent years in the field of metal processing due to its ability to customize material properties and its high geometric freedom which enables the fabrication of complex parts.
These properties make LMD an ideal process for increasing the performance and durability of GJL brake discs in high-stress applications. The coating process applies an extremely durable and wear-resistant 316L stainless steel coating to the surface of the GJL brake disc. This improves both the mechanical and thermal behaviour of the underlying GJL disc and significantly increases its corrosion resistance in corrosive environments [7].
Previous studies have demonstrated the potential of LMD processes to produce high quality 316L stainless steel coatings with refined microstructures and improved mechanical properties. The microstructure of the coatings produced has been extensively characterized and the influence of the LMD process parameters on the results obtained has been studied in detail [8]. In addition, dilatometric studies were carried out to better analyze the thermo-mechanical properties of the multilayer system under varying thermal loads.
The evaluation of grain size, texture appearance, and crystal reorientation on exemplary brake discs was used to assess the material properties and their evolution under thermal and mechanical stress. These microstructural features are critical indicators of performance and durability in coated brake disc in use.
It has been shown that rapid cooling during the LMD process can significantly influence the grain size of the deposited layers. Finer microstructures resulting from rapid solidification typically enhance the strength and hardness of the material [9]. In this context, studies on LMD-processed 316L stainless steel coatings have demonstrated that process parameters such as laser power and scanning speed directly affect grain refinement and mechanical behaviour.
A comprehensive analysis of grain size without and with the brake test provides valuable insights into the effects of thermal cycling and mechanical loading on the microstructure. Recrystallization and grain growth, induced by the heat generated during braking, can degrade the mechanical integrity of the coating [10]. Investigations into LMD coatings under thermal exposure have confirmed that such microstructural changes can reduce hardness and corrosion resistance [10].
In addition to grain size, the crystallographic texture—i.e., the preferential orientation of grains—plays a vital role in determining the anisotropic mechanical properties of polycrystalline materials. Texture evolution can be visualized using pole figures, which graphically represent the orientation distribution of grains. A strong texture may lead to direction-dependent behaviour, which is particularly relevant in layered systems subjected to complex loading conditions [11,12,13]. Alterations in pole figures can thus serve as indicators of microstructural instability or adaptation under service conditions [14].
Prior to testing, a detailed characterization of the microstructure, texture, and pole figures is essential to establish a baseline and verify the uniformity and quality of the coating. Post-test analysis then enables the identification of wear mechanisms, thermal degradation, and plastic deformation. These insights are crucial for optimizing LMD process parameters and improving the long-term performance of coated brake discs [15]. For the sample subjected to the brake test, it is essential to re-evaluate its properties to assess the effects of mechanical loading and heat generation on the material. These investigations can provide information on how the material character changes under real operating conditions. In particular, they can help to identify wear mechanisms, thermal effects and plastic deformation. This information is essential for optimizing LMD process parameters and improving the performance and life of the coatings produced. By combining the pre and post brake test results, valuable insights can be gained that will contribute to the development of more robust and efficient components [16].
This study focuses on the microstructure and EBSD-based analysis of a two-layer 316L stainless steel coating produced via LMD. EBSD is employed to obtain high-resolution data on grain orientation, boundary characteristics, and phase distribution [17]. Previous research has shown that the microstructure and mechanical properties of LMD-processed 316L coatings are highly sensitive to processing conditions [18]. Additionally, the presented study utilizes a brake shock corrosion test, which assesses the durability and performance of brake components under conditions that simulate real-world exposure to corrosive environments and mechanical shock. The aim of this work is to gain a deeper understanding of the microstructure–property relationships in 316L coatings and to evaluate the effects of LMD process parameters on the resulting microstructure without and with a brake shock corrosion test. The aim is to deepen the understanding of microstructure–property relationships and to derive process–structure–performance correlations that can guide future coating design [19].

2. Materials and Methods

The objective of this study was to investigate the feasibility of laser cladding grey cast iron (GJL) 150 with distinct stainless steel alloy, namely 316L, in conjunction with WC particles. A multilayer cladding system was employed to produce the samples.
Figure 1 depicts a three-dimensional representation of the resulting coating system. The first layer was used to increase adhesion and to enhance the corrosion resistance of the surface. The second layer was specified to optimize the wear resistance. The 316L stainless steel powder, with a particle size distribution of 15–55 µm (max. 5% oversize and undersize), was selected for its excellent corrosion resistance and mechanical properties. WC particles, with an average particle size of 5–30 µm, were incorporated to enhance the wear resistance of the coating. The coating thickness ranges between 250–300 µm, while the brake disc substrate has a thickness of approximately 30 mm.
In Table 1 the chemical compositions of the used materials are shown. The chemical composition of the gas atomized powders used to coat the samples was provided by the supplier, Höganäs, Sweden.
The LMD process was carried out using a high-power laser. The laser power was set to 20 kW. The samples consisted of a two-layer structure on grey cast iron brake discs. The first layer was pure 316L stainless steel, and the second layer was 316L reinforced with 25–30 wt.% WC hard particles. The samples investigated are illustrated in Table 2.
Complete coated brake discs were subjected to a brake shock corrosion test in accordance with an automotive test specification. The 1200 brake cycles were conducted over a period of approximately 36 h, following a standardized protocol with defined braking and cooling intervals.
The analyzed specimens were extracted from the coated brake discs, embedded as cross-sections, and subsequently ground and polished for microstructural and electrochemical analysis. The dimensions of the extracted samples were approximately 25 mm × 5 mm × 10 mm from same position of brake disc.
The test brake shock corrosion was conducted directly on full-size brake discs, as sample 3, using an industrial test rig that simulates real driving conditions. The procedure was carried out step-by-step in collaboration with a commercial brake disc manufacturer. The setup comprises the following components:
  • Driving and Braking Simulation System—Simulates vehicle dynamics and enables temperature and rotational speed measurements.
  • Corrosion Salt Spray—Applies corrosive conditions to the brake discs.
  • Damp Heat Chamber—Subjects the samples to cyclic high humidity and temperature.
  • Storage of the Same Brake Disc—Following the completion of the test sequence, the brake disc was stored at ambient room temperature for a duration of 20 h.
  • Sample preparation—Two discs were selected for metallographic analysis: one that underwent the full brake shock corrosion test and one reference disc that was not exposed to the test sequence. Specimens were extracted from both discs.
  • Microstructural characterization.
Due to confidentiality agreements with our industrial partner, we are unable to provide detailed photographs or technical schematics of the experimental setup or disclose specific force application or measurement methods. Nevertheless, the schematic in Figure 2 conceptually illustrates the test procedure and environment step by step. Additionally, Figure 3 illustrates the driving and braking conditions during the initial phase of the test, based on data approved for publication by the manufacturer. This visualization supports the interpretation of the applied stresses and their effects on the coating system.
Figure 3 presents the driving, braking force, and temperature profile recorded during the initial 10 h of test. This figure specifically represents the first step of the overall testing procedure, referred to as the “Drive and brake test on brake disc” as first step of the Brake Shock Corrosion. The test simulates realistic driving conditions, including gradual acceleration, cruising, and intermittent braking events. A total of 1200 braking cycles were performed, with 10 classified as emergency braking events. These emergency braking events caused abrupt deceleration from speeds of up to 120 km/h to values between 0 and 30 km/h, leading to rapid surface temperature spikes reaching approximately 500 °C.
The braking force, shown in arbitrary units (a.u.), reflects the intensity of each braking event and correlates with the thermal response of the coated surface. The upper graph in Figure 3 shows the temperature and rotational speed profile, while the lower graph illustrates the correlation between temperature and braking force. These quantified loading conditions—cyclic thermal expansion and contraction combined with mechanical stress due to frictional contact—are directly responsible for the grain growth and texture evolution observed in the EBSD analysis. This initial phase provides essential mechanical and thermal loading prior to the subsequent corrosion exposure steps and supports the interpretation of microstructural changes under realistic service conditions.
To evaluate the samples, they were separated, vertically embedded in a conductive hot-mounting medium, and subsequently prepared to visualize the microstructure. Mechanical grinding was performed in three stages using medium, fine, and very fine abrasive papers for several minutes in alternating directions. This was followed by fine polishing in two steps using diamond suspensions. First with a grain size of 3 µm, then with 1 µm. Finally, vibratory polishing was carried out for several hours using a vibration polishing unit equipped with a magnetic fixation system. The vibration frequency ranged from 60 to 120 Hz, and a suitable suspension with a particle size of 0.06 µm was used to achieve a high-quality surface finish. The samples were then etched to reveal the microstructure. The samples were treated with a V2A etchant (50% HCl, 10% HNO3, and 40% H2O) at 70 °C with an etching time of 30 s. Microstructural analysis was performed using scanning electron microscopy (SEM ZEISS EVO MA 15, Germany). The grain size and phase distribution were examined using Electron Backscatter Diffraction (EBSD).
EBSD analysis was additionally used to obtain detailed information on grain orientation, grain boundary characteristics, and phase distribution. The EBSD data were collected using an SEM equipped with an EBSD detector Bruker Germany and the samples tilted to 70° using 20 kV acceleration voltage. The resulting data were analyzed using “ESPRIT Analysis version family” software to generate orientation maps, grain boundary maps, and pole figures. In order to test the phases identified in the coated GJL samples, the following phases were used as references: austenite, ferrite, sigma phase and WC. The selection of these phases was made on the basis of their relevance to the microstructural and mechanical properties of the coated GJL samples. The careful examination of these phases is intended to investigate the behaviour of the coating under real conditions and thus determine the effectiveness of the LMD process parameter.
Austenite was selected due to its face-centred cubic (FCC) phase, a structural form commonly observed in stainless steels, including the primary phase in 316L stainless steel. This phase is known for its ability to provide the requisite structural integrity and resistance to environmental factors. Ferrite was selected due to its possible phase transformation in the microstructure of the coating, as well as its influence on the mechanical properties and thermal behaviour of the coating. The sigma phase is an intermetallic compound that can form in stainless steel, particularly under high-temperature conditions. The material is recognized for its brittleness and its detrimental effects on mechanical properties. The presence of sigma phase was investigated because it tends to form during the thermal cycling and mechanical stress encountered during brake tests, thereby impacting the coating’s overall performance. The selection of CrFe was motivated by its propensity to form sigma phase during the laser metal deposition (LMD) process, a phenomenon that exerts a significant influence on the durability and performance of the coating. WC was selected due to its frequent application in conjunction with stainless steel coatings, with the objective of enhancing their performance under severe conditions, such as those encountered during brake tests.
To investigate the mechanical properties of the coating systems and the substrate, microhardness measurements were performed using a Vickers hardness tester HOG-250A Netherlands (HV0.3). For each material (316L, 316L_WC, and GJL substrate), nine measurements (n = 9) were conducted to ensure statistical reliability.
For the GJL substrate, Brinell hardness (HBW) was additionally measured, also with nine repetitions, as this method is more suitable for cast iron due to its coarse and heterogeneous microstructure, which includes lamellar graphite. The larger indentation area of the Brinell method provides more representative value for such materials.
Nevertheless, Vickers microhardness was also applied to the substrate to enable direct comparison with the coating layers.
Furthermore, wedge compression tests were performed on the GJL substrate to estimate its compressive strength. This method is particularly relevant for brake disc materials and was conducted on cut and prepared samples according to VDG340 standards. The compressive strength was used to approximate the tensile strength (Rm).
It should be noted that direct tensile testing of the coating layers was not feasible, as the coating thickness (250–300 µm) is significantly smaller than the substrate thickness (~30 mm), as shown in Figure 1. Therefore, mechanical characterization of the coatings was limited to microhardness testing.

3. Results

To this end, investigations were carried out regarding the influence of the selected application parameters, including change in microstructure development and grain growth with the help of EBSD. Analyzing microstructural evolution and grain growth under service conditions including thermal and mechanical loads is crucial, as these changes directly impact the coating’s performance and longevity. EBSD observations on the cross-sectional surface indicate the presence of a microstructure gradient in the surface mechanical attrition treatment-affected region, consistent with the findings of a prior study [20]. The results generated are shown and discussed in the following sections.

3.1. Microstructural Analysis of 316L Powder

The 316L powder was subjected to V2A etching (50% HCl, 10% HNO3, and 40% H2O) at 70 °C for 30 s to facilitate microstructural analysis using a scanning electron microscope (SEM). Figure 4 shows a backscattered electron detector (BSD) image of an etched 316L powder particle. The enhanced visibility of grain boundaries indicates a well-defined and homogeneous grain structure. This fine and uniform microstructure is beneficial for improving the strength and hardness of the resulting coating, which is advantageous for automotive applications.
Although the manuscript discusses the wear behaviour and dominant crystalline phases of the materials, no X-ray diffraction (XRD) analysis was performed on the etched 316L powder. This is because the etching process was applied solely for surface preparation and does not significantly alter the crystalline structure. The phase composition of 316L stainless steel powder is well established in the literature and is known to consist predominantly of a single austenitic γ-phase. Therefore, additional XRD analysis was not deemed necessary in this context. This is supported by several studies that confirm the stable austenitic phase of 316L powder under standard processing conditions [21,22,23].
The rapid heating and cooling cycles inherent to the LMD process engender residual stress within the material. These stresses are attributed to thermal gradients and the solidification process. These residual stresses have the potential to influence the mechanical properties of 316L stainless steel, potentially resulting in distortion, cracking, or a reduction in fatigue life [24].

3.2. Microstructural Analysis of the First and Second Layer Without and with the Brake Test

Firstly, the SEM images shown in Figure 5 illustrate both coating layers without and with the brake test. Figure 5 reveals distinct microstructural changes in both the first and second coating layers, including grain coarsening and crack formation, which are indicative of thermal and mechanical stress during braking. Recent investigations have demonstrated that microstructural gradients introduced during the LMD process can significantly affect the mechanical behaviour of coated materials under thermal and mechanical loading. For instance, Galgon et al. [25] reported that variations in grain structure and composition within LMD-fabricated γ-TiAl alloys led to localized differences in crack propagation and anisotropic deformation behaviour. These findings underline the importance of understanding grain orientation and texture evolution in functionally graded materials, an aspect that is directly relevant to the microstructural changes observed in the present study following brake shock corrosion testing. To facilitate a more detailed analysis, each layer is shown and examined separately in the subsequent Figure 6, Figure 7 and Figure 8, where the microstructural changes observed in Figure 6—such as grain coarsening, crack formation, and matrix evolution—are analyzed in depth. As illustrated in Figure 5, the evolution of grain misorientation in the initial layer during successive pulsed laser depositions is depicted. This evolution is followed by the outcome of the brake shock corrosion test, which is then analyzed.
Figure 6 illustrates the microstructural changes in the second layer of the sample after undergoing the brake test. Notable changes include grain coarsening, matrix distortion, and the formation of microcracks around WC hard particles, which are indicative of the influence of thermo-mechanical stress during braking. These features have been highlighted in the image using yellow markings. A more detailed analysis of these microstructural changes is provided in Section 3.2, including their correlation with grain orientation and the role of WC reinforcement. The contrast in Figure 6 has been enhanced to improve the visibility of these effects.
As illustrated in Figure 7, the thermomechanical load resulting from braking has been transferred to the first coating layer. In the SEM image on the left (sample without the brake test), several horizontal cracks are visible, which likely result from residual thermal stress during the LMD process. These cracks may act as stress concentrators and negatively impact the mechanical integrity of the coating under cyclic loading conditions. In the sample subjected to the brake test, vertical microcracks—highlighted by the yellow rectangle in the SEM image on the right—are observed propagating from the direction of the substrate. These cracks appear more pronounced and widened, indicating that they have been further activated and opened due to the mechanical and thermal stresses during the brake shock corrosion test.
In Figure 8, the results of the EBSD mappings of the two deposited coating layers are presented. A comparison of the two EBSD maps reveals an increase in the size of the grains, indicating grain growth due to the thermal cycles. Further microstructural details are provided in Section 3.2 and Section 3.3. This observation is accompanied by a change in both layer grain size and texture. The increase in grain size and the evolution of textures suggests that the thermal and mechanical stresses during the brake test promote grain growth and reorientation. However, as shown in Figure 8, the EBSD map obtained after the LMD process and prior to the brake test reveals visibly smaller and more isotropic 316L grains compared to the sample condition after the brake test, indicating grain growth due to the combined effects of thermal and mechanical stress during braking. The microstructures exhibit significant variations depending on the type of carbide incorporated. In particular, the presence of WC leads to a more pronounced grain enlargement in the second layer, even sample without the brake test, suggesting that WC influences grain boundary behaviour and promotes coarser grain structures. This observation is consistent with findings reported in the literature. In the sample subjected to the brake test, both the first and second layers exhibit further grain growth and coarsening, which can be attributed to the combined effects of heat and mechanical stress during braking [20,26].
The microstructure can also represent the as-treated state of the material, since at low temperature the microstructure is rather stable. Furthermore, the surface mechanical attrition treatment does not induce any austenitic phase transformation into martensite in this 316L alloy, as was previously observed in other studies [20,27]. In the study reported on by Zhang et al. [28] the fabrication of a Ni-based superalloy coating was achieved through the process of pulsed laser deposition. The results of the study indicated that most of the grains exhibited an inclination in their growth orientation, with a predominant orientation of <001>. The arrangement of the grains within the coating gives rise to a distinct texture and generates anisotropy, exhibiting a modest angle misorientation of approximately 2°. This is attributable to the direction of the maximum temperature gradient experienced during the pulsed laser deposition process. The study by Wang et al. aims to ascertain the effect of processing parameters on the microstructure and mechanical properties of 304L stainless steel manufactured using the additive manufacturing process [29]. A paucity of literature exists on the grain growth of coating material produced by LMD using different alloy powders in different application conditions.
Ensuring the uniform grain structure of the coating layer on brake discs is paramount to ensure optimal functionality during braking. This involves the formation of equiaxed grains, which is crucial for the even distribution of braking force within the coating. Consequently, it is imperative to maintain a pristine LMD process and to fabricate a brake disc with optimal properties and nearly zero defects in microstructure. Nevertheless, it is crucial to analyze in detail the effects of braking applications on the brake disc material during braking to enable the development of improved process optimization.

3.3. Evaluation of the Grain Size During the Brake Test

The present study was undertaken to evaluate the impact of braking on the microstructure of grey cast iron brake discs. For this purpose, the grain size of the discs was examined using EBSD before and after the brake test. The analysis of the grain size in both coating layers of the tested sample revealed a noticeable increase due to the braking process, as highlighted by the grey box in Figure 9. Specifically, the grain size increased from predominantly below 20 µm before the brake test to values ranging between 30 and 60 µm after testing, indicating significant grain coarsening due to thermomechanical loading. These findings indicate that the braking process influences the grain size distribution, as evidenced by the EBSD maps showing grain coarsening in both coating layers after braking. Similar effects of thermal and mechanical loading on the microstructure of 316L stainless steel have been reported in the literature [30,31]. These alterations were then subjected to thorough analysis to ascertain the correlation between the brake conditions and the microstructural evolution of the grey cast iron [8]. This analysis yielded valuable insights into the material’s performance and durability under operational stresses.
In the sample exposed to the brake test, pronounced grain coarsening was detected, accompanied by the emergence of a distinct crystallographic texture. These observations point to a thermomechanically driven reorientation of grains, likely induced by the combined thermal and mechanical stresses during the test procedure. This phenomenon can be attributed to the combined effects of thermal cycling and mechanical stress. This phenomenon could be indicative of recrystallization and grain growth, which, in turn, may result in alterations in strength and ductility. The literature confirms that thermal cycling and mechanical stress can significantly impact the microstructure of materials. For example, the study on wire-arc additive manufacturing shows that thermal cycling can lead to grain growth and changes in mechanical properties [32]. Literature consistently indicates that recrystallization and grain growth can lead to alterations in mechanical properties. The study on AISI 316 stainless steel specifically notes that these processes can change the material’s strength and ductility [33].

3.4. Pole Figures and Texture Analysis

For the rapid solidification process of pulsed laser deposition, the effects of concentration undercooling, curvature undercooling, thermal undercooling, and anisotropy of interfacial energy on the solidification can be ignored due to the high temperature gradient [34]. Consequently, the dendritic growth orientation is determined by the direction of maximum temperature gradient, which is parallel to the laser deposition direction [35]. The growth orientations of some grains deviate from {001}, indicating a relatively large angle between the direction of laser deposition and grain growth orientation of these grains [36]. The austenite matrix of 316L stainless steel exhibits a face-centred cubic (fcc) crystal structure, with the primary slip system being {111} (<101>) and a preferential growth direction of {001} (<001>). This information is indispensable for understanding the grain growth and texture evolution in the samples under study [37,38].
It has been established that slip systems and growth direction exert an influence on the directional properties of material. This, in turn, affects the manner in which the material deforms and strengthens under stress. The {111} slip planes are the most densely packed planes in the fcc structure, allowing for easier dislocation movement, which contributes to the material’s ductility and toughness [39]. The preferential growth direction {001} (<001>) can lead to anisotropic properties, meaning the mechanical properties such as strength and ductility can vary depending on the direction of the applied force [40].
This is a critical consideration for applications where directional properties are paramount. In the case of 316L alloy, the grain exhibits growth in the orientation of <001>, with the direction of maximum temperature gradient approximately perpendicular to the substrate surface. The growth orientations of certain dendrites in the bottom region of the coating are not perpendicular to the coating-substrate interface. The “bottom region of the coating” is defined as the part of the coating that is in closest proximity to the substrate, which is the underlying material or surface to which the coating is applied. This region is of particular significance because the interaction between the coating and the substrate can have a substantial impact on the overall properties and performance of the coating [41]. Variations in grain orientation and dendrite growth in this area can affect the mechanical properties, such as strength and ductility, of the coating. This variation in orientation can be attributed to the non-perpendicular orientation of grains on the substrate surface [42]. The orientation of grains can result in varying mechanical properties. For example, grains aligned with the {001} direction may exhibit higher strength and lower ductility compared to other orientations [43]. It is imperative to comprehend anisotropic behaviour for applications necessitating specific mechanical properties, such as in high-stress environments or components subjected to directional forces. This phenomenon can be elucidated by the effect of grain orientation on strength and ductility as well as corrosion resistance [44]. The grain orientation can also affect the corrosion resistance of 316L stainless steel, with certain orientations providing better resistance in specific environments [45]. The literature confirms that orientations such as {111} and {110} provide better corrosion resistance due to their atomic arrangement and surface energy characteristics [46].
The transition from the initial texture formed during the LMD process to a more pronounced crystallographic texture in the sample subjected to the brake test (as shown in Figure 10 and Figure 11) indicates a stress-induced reorientation of grains. This evolution suggests that the combined thermal and mechanical loads during the test significantly influenced the microstructural alignment. This reorientation can influence the material’s mechanical properties, potentially enhancing strength in specific directions while reducing it in others [47]. The development of a preferred grain orientation (texture) can result in anisotropic properties, where the material’s strength and ductility vary depending on the direction of the applied force [48]. During the braking process, elevated temperatures and mechanical stresses can induce alterations in the microstructure of the coating, thereby affecting grain size and dendrite orientation. These alterations can influence the mechanical properties of the coating, potentially enhancing strength in specific directions while reducing it in others, leading to anisotropic properties where the material’s strength and ductility vary depending on the direction of the applied force. This phenomenon is influenced by the thermal gradients during braking and solidification dynamics during the process [28,49].
By comparing the pole figures and IPFs without and with the brake test, it can be concluded that thermal and mechanical stress significantly influences the grain orientation and texture of the first layer. These observations are critical for comprehending the material’s behaviour under real-world conditions and enhancing the performance of the LMD process. By understanding and optimizing the factors that affect grain orientation and texture, the performance of the LMD process can be significantly improved, leading to higher quality and more reliable components [37,38].
As previously outlined in the publications [3,8], the interface between the substrate and the first layer of the sample subjected to the brake test presents a significant challenge, particularly in terms of achieving metallurgical bonding and structural integrity under thermomechanical loading. In the EBSD phase maps shown in Figure 10 and Figure 11, an increasing number of zero solutions was observed in the tested samples. This phenomenon is primarily attributed to the presence of non-austenitic phases within the microstructure, such as carbides or oxides, which do not index to austenite. These phases likely formed or became more pronounced due to the thermal and mechanical stresses during braking. Although grain size can also influence indexing quality, the dominant factor in this case is the presence of additional phases that are not resolved by the austenitic indexing parameters.
As demonstrated in Figure 12, the sample subjected to the brake test—highlighted in the yellow box—exhibits numerous microcracks originating from the substrate direction, indicating a critical phenomenon that merits further investigation. This phenomenon suggests a potential modification of the grain boundary. A grain boundary where the growing dendrites of neighbouring grains are inclined towards each other in the direction of growth (so-called converging GRAIN BOUNDARY) promotes the unfavourably oriented grain, while a grain boundary where the dendrites grow away from each other (so-called diverging GRAIN BOUNDARY) tends to cause unfavourably oriented grains to become overgrown [50].
A comparable mechanism has been delineated in the publication by Sun [51]. It is imperative to undertake a comprehensive analysis of this mechanism both prior to and following the braking test. As illustrated in a modified form in Figure 12, the arrangement of the converging and diverging GBs under the influence of mechanical and thermal stress during braking is shown in panels a1 to a3 (Figure 12 left) sample without the braking test and panels b1 to b3 (Figure 12 right) sample with the braking test.
The textured grain with the <001> orientation is observed to be predominant in the converging grain boundary under the influence of mechanical and thermal stress during the braking process (see Figure 12(a1–a3)). Guo et al. have demonstrated through phase field simulations that this phenomenon occurs under specific conditions, namely when the misorientation angle (α), defined as the smallest angle between the fast-growing <001> directions of the two competing crystals, is sufficiently small [52].
It is reasonable to hypothesize that the <101> textured grain will begin to overgrow its <001> counterpart. Overgrowth can develop obliquely and maintain orientation, presumably because there are more choices for the preferred crystallographic growth directions (see Figure 10a and Figure 11a). If the grains continue to grow adjacent to a converging grain boundary and toward a curved melt pool (Figure 12(a3)), they will have a greater number of growth directions to grow under similar orientations. However, the other grains will also have different orientations or will continue to grow due to the thermal stress. This illustration can also be seen in Figure 12(b3).

3.5. Mechanical Properties

The microhardness values of the coatings and substrate were evaluated in both sample 2 and 3 without and with the Brake Shock Corrosion Test. A slight decrease in hardness was observed in sample 3, which can be attributed to thermally induced grain growth. According to the Hall–Petch relationship, larger grains reduce the number of grain boundaries, which act as barriers to dislocation movement. This leads to a reduction in hardness and mechanical strength [53]. In contrast, the presence of WC particles in the 316L_WC coating appears to stabilize the hardness, indicating their reinforcing effect under thermal and mechanical stress [54]. This effect is further supported by recent studies showing that WC particles not only improve wear resistance but also contribute to maintaining mechanical integrity under cyclic loading and elevated temperatures [55]. A comparison of the first layer with the second layer of both samples shows that although both layers have the same 316L matrix, the second layer is harder than the first layer due to the influence of WC as a hard particle. However, it has been shown that the hardness of the second layer of sample 3 decreases compared to sample 2 without brake impact corrosion testing due to stress or grain growth. The measured mechanical properties are summarized in Table 3.
Figure 13 presents the average microhardness values (HV0.3, n = 9) of the substrate and both coating systems.

4. Discussion

In the sample without the brake test, the first layer exhibits a uniform grain structure with fine, equiaxed grains and well-defined grain boundaries (Figure 5). The sample exposed to the brake test exhibited substantial microstructural changes and a noticeable shift in grain orientation, suggesting that the combined thermal and mechanical loads during testing played a decisive role in driving grain reconfiguration. Thermal cycling and mechanical stress during the brake test promote grain growth and reorientation, resulting in an increase in grain size (Figure 9) and the development of a new texture (Figure 8). Overall, the microstructural analysis reveals that the fine and uniform grains of 316L powder contribute to its favourable mechanical properties, which are further enhanced by the laser deposition process. However, the brake test induces significant microstructural changes, which can affect the material’s strength and ductility [56,57]. This suggests that the microstructure of 316L stainless steel is sensitive to such conditions, impacting on its long-term stability and performance [58].
The transition from the LMD-induced texture to a more pronounced <101> orientation in the tested sample suggests stress-induced reorientation, which can enhance strength in specific directions while reducing it in others [59,60].
In 316L, grains tend to grow along <001>, aligned with the thermal gradient. Deviations near the substrate are attributed to the initial grain orientation of the base material [59,61,62].
Phase maps (Figure 10 and Figure 11) confirm the stability of the austenitic FCC structure in both conditions, with no phase transformation observed [63]. The austenite matrix of 316L stainless steel exhibits a face-centred cubic (FCC) crystal structure, with the primary slip system being {111} (<101>) and a preferential growth direction of {001} (<001>). This information is indispensable for understanding grain growth and texture evolution in the samples under study [44].
The emergence of anisotropy in the tested sample may lead to direction-dependent mechanical behaviour [64].
The study highlights the importance of understanding how thermal cycling and mechanical stress influence the microstructure and properties of coatings. This knowledge is crucial for designing coatings that can withstand the harsh conditions encountered in real-world applications, such as automotive braking systems [65,66].
Microhardness measurements (Table 3, Figure 13) showed a slight decrease after testing, particularly in the second layer of sample 3, due to thermally induced grain growth. This aligns with the Hall–Petch relationship, where fewer grain boundaries reduce resistance to dislocation motion [53].
The presence of WC particles helped stabilize hardness under stress, confirming their reinforcing effect [54,55]. Although both layers share the same 316L matrix, the second layer exhibited higher hardness due to the WC reinforcement. However, after exposure to braking and corrosion, the hardness of the second layer in sample 3 decreased, indicating stress-induced softening or grain coarsening.
These findings underscore the need to consider both microstructural and mechanical responses when evaluating coating performance under realistic service conditions. The correlation between grain structure, texture, and hardness provides a comprehensive understanding of the material’s behaviour and its limitations in demanding environments.
The observed increase in hardness and reduction in crack density, particularly in the WC-reinforced layer, suggest improved wear resistance. This microstructural stability under thermomechanical stress may contribute to lower particle emissions during braking, as fewer wear particles are likely to be generated from harder, more intact surfaces. These findings support the engineering relevance of microstructural optimization in reducing brake dust emissions [67,68].

5. Conclusions

This study demonstrates the effectiveness of applying a two-layer 316L stainless steel coating on grey cast iron (GJL) using Laser Metal Deposition (LMD) to investigate microstructural changes under braking force in a corrosive environment. The results show that thermal cycling and mechanical stress during braking lead to grain growth from below 20 µm to 30–60 µm, reorientation, and texture evolution toward <101> orientation, particularly in WC-reinforced layers.
Advanced characterization techniques such as SEM and EBSD revealed a transition from fine equiaxed grains to elongated grains with preferred orientations, indicating service-induced transformations. These microstructural changes correlate with a slight decrease in hardness, especially in the second layer of sample 3, consistent with the Hall–Petch relationship. The presence of WC particles helped stabilize hardness under stress, confirming their reinforcing effect. However, after the brake test, it was found that the WC-reinforced second layer had become weaker, dropping from 478 HV to 432 HV. The 316L first layer also got weaker, from 232 HV to 223 HV.
The findings highlight the importance of evaluating both microstructural and mechanical responses under realistic service conditions. The observed correlation between grain structure, texture evolution, and hardness provides valuable insight into the coating’s performance and limitations.
Limitations: Due to industrial confidentiality, detailed loading profiles and mechanical property data could not be disclosed, limiting direct quantitative correlations.
Outlook: Future work will focus on in situ mechanical testing under controlled thermal-mechanical conditions and advanced synchrotron-based techniques to investigate real-time microstructural responses during simulated braking.
Future Perspectives: The study of the microstructure and mechanical properties of 316L stainless steel with and without the brake test provides valuable insights into the effects of thermal and mechanical stresses. Future research could focus on understanding the mechanisms of grain growth and reorientation to improve material properties. Advanced characterization techniques, such as in situ SEM and synchrotron X-ray diffraction, could be used to observe microstructural changes in real-time. Additionally, exploring the anisotropy of mechanical properties and controlling texture could lead to tailored materials for specific applications.

Author Contributions

This research article is written by several authors with the following contributions: Conceptualization, M.M.; Methodology, M.M.; Validation, M.M., A.C., H.P. and H.M.-J.; Formal analysis, M.M. and A.C.; Investigation, M.M. and A.C.; Resources, M.M., A.C., H.P. and H.M.-J.; Data curation, M.M. and A.C.; Writing—original draft preparation, M.M.; Writing—review and editing, M.M., A.C., H.P. and H.M.-J.; Visualization, M.M. and A.C.; Supervision, H.P. and H.M.-J.; Project administration, M.M., H.P. and H.M.-J.; Funding acquisition, M.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All required data in this article have only been published here and should be considered with respect to copyright.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Franke, S. Gießerei Lexikon, 13th ed.; Schiele & Schön: Berlin, Germany, 2019. [Google Scholar]
  2. Weißbach, W.; Dahms, M.; Jaroschek, C. Werkstoffe und Ihre Anwendungen; Springer Vieweg Wiesbaden: Wiesbaden, Germany, 2005; ISBN 978-3-658-19892-3. [Google Scholar]
  3. Masafi, M.; Palkowski, H.; Mozaffari-Jovein, H. Micro-Friction Mechanism Characterization of Particle-Reinforced Multilayer Systems of 316L and 430L Alloys on Grey Cast Iron. J. Mater. Res. Technol. 2024, 33, 6090–6101. [Google Scholar] [CrossRef]
  4. Zhang, Y.; Wu, L.; Guo, X.; Kane, S.; Deng, Y.; Jung, Y.-G.; Lee, J.-H.; Zhang, J. Additive Manufacturing of Metallic Materials: A Review. J. Mater. Eng. Perform. 2018, 27, 1–13. [Google Scholar] [CrossRef]
  5. Ascari, A.; Lutey, A.H.A.; Liverani, E.; Fortunato, A. Laser Directed Energy Deposition of Bulk 316L Stainless Steel. Lasers Manuf. Mater. Process. 2020, 7, 426–448. [Google Scholar] [CrossRef]
  6. Park, J.; Kim, J.; Ji, I.; Lee, S.H. Numerical and Experimental Investigations of Laser Metal Deposition (LMD) Using STS 316L. Appl. Sci. 2020, 10, 4874. [Google Scholar] [CrossRef]
  7. Badoniya, P.; Srivastava, M.; Jain, P.K.; Rathee, S. A State-of-the-Art Review on Metal Additive Manufacturing: Milestones, Trends, Challenges and Perspectives. J. Braz. Soc. Mech. Sci. Eng. 2024, 46, 339. [Google Scholar] [CrossRef]
  8. Masafi, M.; Palkowski, H.; Mozaffari-Jovein, H. Microstructural Properties of Particle-Reinforced Multilayer Systems of 316L and 430L Alloys on Gray Cast Iron. Coatings 2023, 13, 1450. [Google Scholar] [CrossRef]
  9. Aversa, A.; Marchese, G.; Bassini, E. Directed Energy Deposition of AISI 316L Stainless Steel Powder: Effect of Process Parameters. Metals 2021, 11, 932. [Google Scholar] [CrossRef]
  10. Krakhmalev, P.; Fredriksson, G.; Svensson, K.; Yadroitsev, I.; Yadroitsava, I.; Thuvander, M.; Peng, R. Microstructure, Solidification Texture, and Thermal Stability of 316 L Stainless Steel Manufactured by Laser Powder Bed Fusion. Metals 2018, 8, 643. [Google Scholar] [CrossRef]
  11. Hagihara, K.; Nakano, T. Control of Anisotropic Crystallographic Texture in Powder Bed Fusion Additive Manufacturing of Metals and Ceramics—A Review. JOM 2022, 74, 1760–1773. [Google Scholar] [CrossRef]
  12. DeNonno, O.; Saville, A.; Benzing, J.; Klemm-Toole, J.; Yu, Z. Solidification Behavior and Texture of 316L Austenitic Stainless Steel by Laser Wire Directed Energy Deposition. Mater. Charact. 2024, 211, 113916. [Google Scholar] [CrossRef]
  13. Kuzminova, Y.O.; Evlashin, S.A.; Belyakov, A.N. On the Texture and Strength of a 316L Steel Processed by Powder Bed Fusion. Mater. Sci. Eng. A 2024, 913, 147026. [Google Scholar] [CrossRef]
  14. Yuan, R. Effects of Grain Size, Texture and Grain Growth Capacity Gradients on the Deformation Mechanisms and Mechanical Properties of Gradient Nanostructured Nickel. Acta Mech. 2023, 234, 4147–4181. [Google Scholar] [CrossRef]
  15. Lita, A.E.; Sanchez, J.E. Effects of Grain Growth on Dynamic Surface Scaling during the Deposition of Al Polycrystalline Thin Films. Phys. Rev. B 2000, 61, 7692–7699. [Google Scholar] [CrossRef]
  16. Alemani, M.; Nosko, O.; Metinoz, I.; Olofsson, U. A Study on Emission of Airborne Wear Particles from Car Brake Friction Pairs. SAE Int. J. Mater. Manuf. 2015, 9, 147–157. [Google Scholar] [CrossRef]
  17. Xia, X.; Wu, J.; Liu, Z.; Ma, J.; Ji, H. EBSD Analysis of 316L Stainless Steel Weldment on Fusion Reactor Vacuum Vessel. Trans. Indian Inst. Met. 2023, 76, 3379–3391. [Google Scholar] [CrossRef]
  18. Shamsujjoha, M.; Agnew, S.R.; Fitz-Gerald, J.M.; Moore, W.R.; Newman, T.A. High Strength and Ductility of Additively Manufactured 316L Stainless Steel Explained. Metall. Mater. Trans. A 2018, 49, 3011–3027. [Google Scholar] [CrossRef]
  19. Bayode, A.; Akinlabi, E.T.; Pityana, S. Characterization of Laser Metal Deposited 316L Stainless Steel. In Proceedings of the World Congress on Engineering 2016, Imperial College, London, London, UK, 29 June–1 July 2016; Ao, S.-I., Gelman, L., Hukins, D.W.L., Eds.; Newswood Limited: Hong Kong, China, 2016; Volume II, ISBN 978-988-14048-0-0. ISSN 2078-0958 (Print), 2078-0966 (Online). [Google Scholar]
  20. Sun, Z.; Retraint, D.; Baudin, T.; Helbert, A.L.; Brisset, F.; Chemkhi, M.; Zhou, J.; Kanouté, P. Experimental Study of Microstructure Changes Due to Low Cycle Fatigue of a Steel Nanocrystallised by Surface Mechanical Attrition Treatment (SMAT). Mater. Charact. 2017, 124, 117–121. [Google Scholar] [CrossRef]
  21. Vaz, R.F.; Silvello, A.; Sanchez, J.; Albaladejo, V.; Cano, I.G. The Influence of the Powder Characteristics on 316L Stainless Steel Coatings Sprayed by Cold Gas Spray. Coatings 2021, 11, 168. [Google Scholar] [CrossRef]
  22. Yan, J.; Zhou, Y.; Gu, R.; Zhang, X.; Quach, W.-M.; Yan, M. A Comprehensive Study of Steel Powders (316L, H13, P20 and 18Ni300) for Their Selective Laser Melting Additive Manufacturing. Metals 2019, 9, 86. [Google Scholar] [CrossRef]
  23. Zhang, X.; Zhang, L.; Ma, C.; Hai, X.; Song, K. 316L Austenitic Stainless Steel Deformation Organization and Nitriding-Strengthened Layer Relationships. Appl. Sci. 2025, 15, 2352. [Google Scholar] [CrossRef]
  24. Shi, H.-J.; Wang, Z.-G.; Su, H.-H. Thermomechanical Fatigue of a 316L Austenittc Steel at Two Different Temperature Intervals. Scr. Mater. 1996, 35, 1107–1113. [Google Scholar] [CrossRef]
  25. Galgon, F.; Melzer, D.; Zenk, C.; Džugan, J.; Körner, C. Miniature Mechanical Testing of LMD-Fabricated Compositionally & Microstructurally Graded γ Titanium Aluminides. J. Mater. Res. 2022, 37, 4312–4325. [Google Scholar] [CrossRef]
  26. Proust, G.; Retraint, D.; Chemkhi, M.; Roos, A.; Demangel, C. Electron Backscatter Diffraction and Transmission Kikuchi Diffraction Analysis of an Austenitic Stainless Steel Subjected to Surface Mechanical Attrition Treatment and Plasma Nitriding. Microsc. Microanal. 2015, 21, 919–926. [Google Scholar] [CrossRef] [PubMed]
  27. Proust, G.; Trimby, P.; Piazolo, S.; Retraint, D. Characterization of Ultra-Fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction. J. Vis. Exp. 2017, 122, 55506. [Google Scholar] [CrossRef]
  28. Zhang, Y.; Yang, L.; Dai, J.; Huang, Z.; Meng, T. Grain Growth of Ni-Based Superalloy IN718 Coating Fabricated by Pulsed Laser Deposition. Opt. Laser Technol. 2016, 80, 220–226. [Google Scholar] [CrossRef]
  29. Wang, Z.; Palmer, T.A.; Beese, A.M. Effect of Processing Parameters on Microstructure and Tensile Properties of Austenitic Stainless Steel 304L Made by Directed Energy Deposition Additive Manufacturing. Acta Mater. 2016, 110, 226–235. [Google Scholar] [CrossRef]
  30. Liu, W.; Hu, G.; Yan, Z.; Liu, B.; Wang, T.; Lyu, Z. Thermal Effect on Microstructure and Mechanical Properties in Directed Energy Deposition of AISI 316L. Int. J. Adv. Manuf. Technol. 2024, 134, 3337–3353. [Google Scholar] [CrossRef]
  31. Petroušek, P.; Kvačkaj, T.; Bidulská, J.; Bidulský, R.; Grande, M.A.; Manfredi, D.; Weiss, K.-P.; Kočiško, R.; Lupták, M.; Pokorný, I. Investigation of the Properties of 316L Stainless Steel after AM and Heat Treatment. Materials 2023, 16, 3935. [Google Scholar] [CrossRef]
  32. Vlasov, I.; Gordienko, A.; Kuznetsova, A.; Semenchuk, V. Effects of Heat Input and Thermal Cycling on the Microstructure and Mechanical Properties of Steel Walls Built by Wire-Arc Additive Manufacturing. Metallogr. Microstruct. Anal. 2025, 14, 229–244. [Google Scholar] [CrossRef]
  33. Di Schino, A.; Kenny, J.M.; Abbruzzese, G. Analysis of the Recrystallization and Grain Growth Processes in AISI 316 Stainless Steel. J. Mater. Sci. 2002, 37, 5291–5298. [Google Scholar] [CrossRef]
  34. Duff, W.H.; Zhigilei, L.V. Computational Study of Cooling Rates and Recrystallization Kinetics in Short Pulse Laser Quenching of Metal Targets. J. Phys. Conf. Ser. 2007, 59, 413–417. [Google Scholar] [CrossRef]
  35. Chen, Y.; Zhang, Q.; Guo, Y.; Zhang, Q.; Wang, L.; Yao, J.; Kovalenko, V. Dendritic Growth Transition During Laser Rapid Solidification of Nickel-Based Superalloy. JOM 2021, 73, 1538–1545. [Google Scholar] [CrossRef]
  36. Wang, Q.; Zhang, S.; Zhang, C.H.; Wu, C.; Wang, J.; Chen, J.; Sun, Z. Microstructure Evolution and EBSD Analysis of a Graded Steel Fabricated by Laser Additive Manufacturing. Vacuum 2017, 141, 68–81. [Google Scholar] [CrossRef]
  37. Yan, Y.; Feng, L.; Zhang, K.; Wen, J. Influence of Temperature on Creep Behavior of Ag Particle Enhancement SnCu Based Composite Solder. Tsinghua Sci. Technol. 2007, 12, 296–301. [Google Scholar] [CrossRef]
  38. Mokadem, S.; Bezençon, C.; Hauert, A.; Jacot, A.; Kurz, W. Laser Repair of Superalloy Single Crystals with Varying Substrate Orientations. Metall. Mater. Trans. A 2007, 38, 1500–1510. [Google Scholar] [CrossRef]
  39. Rojas Dorantes, C.A.; Czekanski, A. Compaction Effects on the Thermal Properties of Stainless Steel 316L Powders in 3D Printing Processes. Int. J. Adv. Manuf. Technol. 2025, 137, 3877–3886. [Google Scholar] [CrossRef]
  40. Chen, B.; Bai, Y.; Tao, H.; Fu, Q.; Xiong, L.; Weng, J.; Wang, S.; Zhao, H.; Han, Y.; Ding, J. Anisotropic Optoelectronic Properties of MAPbI3 on (100), (112) and (001) Facets. J. Electron. Mater. 2021, 50, 6881–6887. [Google Scholar] [CrossRef]
  41. Drory, M.D.; Hutchinson, J.W. Measurement of the Adhesion of a Brittle Film on a Ductile Substrate by Indentation. Proc. R. Soc. Lond. 1996, 452, 2319–2341. [Google Scholar]
  42. Mohanty, R.; Khan, A.R. Challenges During Scale-up in Wurster Coating. Int. J. Creat. Res. Thoughts 2020, 8, 2071–2078. [Google Scholar]
  43. Byun, T.S.; Lach, T.G. Mechanical Properties of 304L and 316L Austenitic Stainless Steels after Thermal Aging for 1500 Hours Cast Stainless Steel Aging (LW-16OR040215); U.S. Department of Energy: Washington, DC, USA, 2016. [Google Scholar]
  44. Zhi, H.R.; Zhao, H.T.; Zhang, Y.F.; Dampilon, B. Microstructure and Crystallographic Texture of Direct Energy Deposition Printed 316L Stainless Steel. Dig. J. Nanomater. Biostruct. 2023, 18, 1293–1303. [Google Scholar] [CrossRef]
  45. Luecke, W.E.; Slotwinski, J.A. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing. J. Res. Natl. Inst. Stand. Technol. 2014, 119, 398–418. [Google Scholar] [CrossRef]
  46. Hanbury, R.D.; Was, G.S. Effect of Grain Orientation on Irradiation Assisted Corrosion of 316L Stainless Steel in Simulated PWR Primary Water. In Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems–Water Reactors, Boston, MA, USA, 18–22 August 2019; pp. 2303–2312. [Google Scholar]
  47. Li, Q. Anisotropic Mechanical Properties of 2-D Materials. In Plastic Deformation in Materials [Working Title]; IntechOpen: London, UK, 2021. [Google Scholar]
  48. Jacek, J.; Skrzypek, A.W.G. Mechanics of Anisotropic Materials; Skrzypek, J.J., Ganczarski, A.W., Eds.; Springer International Publishing: Cham, Switzerland, 2015; ISBN 978-3-319-17159-3. [Google Scholar]
  49. Jang, W.-L.; Wang, T.-S.; Lai, Y.-F.; Lin, K.-L.; Lai, Y.-S. The Performance and Fracture Mechanism of Solder Joints under Mechanical Reliability Test. Microelectron. Reliab. 2012, 52, 1428–1434. [Google Scholar] [CrossRef]
  50. Zhou, Y.Z.; Volek, A.; Green, N.R. Mechanism of Competitive Grain Growth in Directional Solidification of a Nickel-Base Superalloy. Acta Mater. 2008, 56, 2631–2637. [Google Scholar] [CrossRef]
  51. Sun, Z.; Tsai, S.-P.; Konijnenberg, P.; Wang, J.-Y.; Zaefferer, S. A Large-Volume 3D EBSD Study on Additively Manufactured 316L Stainless Steel. Scr. Mater. 2024, 238, 115723. [Google Scholar] [CrossRef]
  52. Guo, C.; Takaki, T.; Sakane, S.; Ohno, M.; Shibuta, Y.; Mohri, T. Overgrowth Behavior at Converging Grain Boundaries during Competitive Grain Growth: A Two-Dimensional Phase-Field Study. Int. J. Heat. Mass. Transf. 2020, 160, 120196. [Google Scholar] [CrossRef]
  53. Naik, S.N.; Walley, S.M. The Hall–Petch and Inverse Hall–Petch Relations and the Hardness of Nanocrystalline Metals. J. Mater. Sci. 2020, 55, 2661–2681. [Google Scholar] [CrossRef]
  54. Zhang, Y.; Lv, D.; Tian, L.; Chen, K. Effect of WC Particle Addition on the Wear Resistance of FeCoNiAlTi Coatings. J. Mater. Eng. Perform. 2024, 34, 18367–18377. [Google Scholar] [CrossRef]
  55. Liu, S.; Zhu, Y.; Lai, X.; Zheng, X.; Jia, R.; Yuan, X. Influence of Different Heat Treatment Temperatures on the Microstructure, Corrosion, and Mechanical Properties Behavior of Fe-Based Amorphous/Nanocrystalline Coatings. Coatings 2019, 9, 858. [Google Scholar] [CrossRef]
  56. Nastac, M.; Lucas, R.; Klein, A. Microstructure and Mechanical Properties Comparison of 316L Parts Produced by Different Additive Manufacturing Processes; University of Texas at Austin: Austin, TX, USA, 2017. [Google Scholar]
  57. Radhamani, A.V.; Lau, H.C.; Ramakrishna, S. 316L Stainless Steel Microstructural, Mechanical, and Corrosion Behavior: A Comparison Between Spark Plasma Sintering, Laser Metal Deposition, and Cold Spray. J. Mater. Eng. Perform. 2021, 30, 3492–3501. [Google Scholar] [CrossRef]
  58. Fonda, R.W.; Rowenhorst, D.J.; Feng, C.R.; Levinson, A.J.; Knipling, K.E.; Olig, S.; Ntiros, A.; Stiles, B.; Rayne, R. The Effects of Post-Processing in Additively Manufactured 316L Stainless Steels. Metall. Mater. Trans. A 2020, 51, 6560–6573. [Google Scholar] [CrossRef]
  59. Dolzhenko, P.; Tikhonova, M.; Odnobokova, M.; Kaibyshev, R.; Belyakov, A. On Grain Boundary Engineering for a 316L Austenitic Stainless Steel. Metals 2022, 12, 2185. [Google Scholar] [CrossRef]
  60. Chen, P.; Jin, K.; Liu, X.; Qiao, X.; Yang, W. Tribological Performance of Textured 316L Stainless Steel Prepared by Selective Laser Melting. J. Mater. Eng. Perform. 2025, 34, 461–472. [Google Scholar] [CrossRef]
  61. Hassine, N.; Chatti, S.; Kolsi, L. Tailoring Grain Structure Including Grain Size Distribution, Morphology, and Orientation via Building Parameters on 316L Parts Produced by Laser Powder Bed Fusion. Int. J. Adv. Manuf. Technol. 2024, 131, 4483–4498. [Google Scholar] [CrossRef]
  62. He, Q.; Xia, S.; Bai, Q.; Zhang, Y.; Li, L. The Recrystallization Nucleation Mechanism for a Low-Level Strained 316L Stainless Steel and Its Implication to Twin-Induced Grain Boundary Engineering. Metall. Mater. Trans. A 2024, 55, 4525–4542. [Google Scholar] [CrossRef]
  63. Nalepka, K.; Skoczeń, B.; Ciepielowska, M.; Schmidt, R.; Tabin, J.; Schmidt, E.; Zwolińska-Faryj, W.; Chulist, R. Phase Transformation in 316L Austenitic Steel Induced by Fracture at Cryogenic Temperatures: Experiment and Modelling. Materials 2020, 14, 127. [Google Scholar] [CrossRef] [PubMed]
  64. Zhou, Z.-P.; Tan, Z.-H.; Lv, J.-L.; Zhang, S.-Y.; Liu, D. Effect of Annealing and Strain Rate on the Microstructure and Mechanical Properties of Austenitic Stainless Steel 316L Manufactured by Selective Laser Melting. Adv. Manuf. 2024, 13, 634–654. [Google Scholar] [CrossRef]
  65. Cui, L.; Jiang, F.; Deng, D.; Xin, T.; Sun, X.; Mousavian, R.T.; Peng, R.L.; Yang, Z.; Moverare, J. Cyclic Response of Additive Manufactured 316L Stainless Steel: The Role of Cell Structures. Scr. Mater. 2021, 205, 114190. [Google Scholar] [CrossRef]
  66. Mirkoohi, E.; Sievers, D.E.; Garmestani, H.; Liang, S.Y. Thermo-Mechanical Modeling of Thermal Stress in Metal Additive Manufacturing Considering Elastoplastic Hardening. CIRP J. Manuf. Sci. Technol. 2020, 28, 52–67. [Google Scholar] [CrossRef]
  67. Verma, P.C.; Saurabh, A.; Manoj, A.; Saravanan, P.; Sarraf, S.; Tiwari, S.K. Wear Debris from Automotive Brake Pad-Disc System: A Critical Review and Future Prospects. Proc. Inst. Mech. Eng. Part J J. Eng. Tribol. 2025. [Google Scholar] [CrossRef]
  68. Wahlström, J.; Lyu, Y.; Matjeka, V.; Söderberg, A. A Pin-on-Disc Tribometer Study of Disc Brake Contact Pairs with Respect to Wear and Airborne Particle Emissions. Wear 2017, 384–385, 124–130. [Google Scholar] [CrossRef]
Coatings 15 01106 g001
Figure 1. The fabrication of the sample is depicted schematically in three dimensions. Two coatings are applied to the substrate: 316L followed by 316L with hard particles WC. The two coating layers are designated as the first layer and the second layer, respectively.
Figure 1. The fabrication of the sample is depicted schematically in three dimensions. Two coatings are applied to the substrate: 316L followed by 316L with hard particles WC. The two coating layers are designated as the first layer and the second layer, respectively.
Coatings 15 01106 g001
Coatings 15 01106 g002
Figure 2. Schematic representation of the brake shock corrosion test procedure, including thermal, mechanical, and corrosive exposures, as well as sample extraction.
Figure 2. Schematic representation of the brake shock corrosion test procedure, including thermal, mechanical, and corrosive exposures, as well as sample extraction.
Coatings 15 01106 g002
Coatings 15 01106 g003
Figure 3. Driving, braking force, and temperature profile during the initial 10 h of the first step (“Drive and brake test on brake disc”) of the brake shock corrosion test.
Figure 3. Driving, braking force, and temperature profile during the initial 10 h of the first step (“Drive and brake test on brake disc”) of the brake shock corrosion test.
Coatings 15 01106 g003
Coatings 15 01106 g004
Figure 4. SEM image of the etched 316L powder after treatment with V2A etchant. The grain boundaries are clearly visible. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Figure 4. SEM image of the etched 316L powder after treatment with V2A etchant. The grain boundaries are clearly visible. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Coatings 15 01106 g004
Coatings 15 01106 g005
Figure 5. SEM images of the multilayer coating without and with the braking test, showing microstructural changes in the cross-section. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Figure 5. SEM images of the multilayer coating without and with the braking test, showing microstructural changes in the cross-section. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Coatings 15 01106 g005
Coatings 15 01106 g006
Figure 6. SEM images of the second coating layer without and with the braking test, highlighting microstructural evolution due to thermal and mechanical loading. Yellow markings indicate areas of grain coarsening and microcrack formation around WC particles. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Figure 6. SEM images of the second coating layer without and with the braking test, highlighting microstructural evolution due to thermal and mechanical loading. Yellow markings indicate areas of grain coarsening and microcrack formation around WC particles. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Coatings 15 01106 g006
Coatings 15 01106 g007
Figure 7. SEM images of the first coating layer before and after the brake test. The left image (sample without test) shows horizontal cracks, likely caused by residual thermal stress during the LMD process. The right image (sample after test) highlights vertical microcracks (yellow rectangle) propagating from the substrate direction toward the surface. These cracks have widened due to brake-induced mechanical stress. Orientation annotations have been added to clarify the spatial relationship between the coating surface and the substrate. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Figure 7. SEM images of the first coating layer before and after the brake test. The left image (sample without test) shows horizontal cracks, likely caused by residual thermal stress during the LMD process. The right image (sample after test) highlights vertical microcracks (yellow rectangle) propagating from the substrate direction toward the surface. These cracks have widened due to brake-induced mechanical stress. Orientation annotations have been added to clarify the spatial relationship between the coating surface and the substrate. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Coatings 15 01106 g007
Coatings 15 01106 g008
Figure 8. EBSD IPF-X maps of both coating layers before and after the brake test, including phase legend and layer annotations. The maps highlight the influence of WC reinforcement on grain morphology in the second layer, as well as the grain coarsening and texture evolution induced by thermal and mechanical stress during braking. The annotated layers clarify the spatial arrangement of the coating system and support the interpretation of microstructural changes.
Figure 8. EBSD IPF-X maps of both coating layers before and after the brake test, including phase legend and layer annotations. The maps highlight the influence of WC reinforcement on grain morphology in the second layer, as well as the grain coarsening and texture evolution induced by thermal and mechanical stress during braking. The annotated layers clarify the spatial arrangement of the coating system and support the interpretation of microstructural changes.
Coatings 15 01106 g008
Coatings 15 01106 g009
Figure 9. EBSD grain size distribution of the coating layers before and after the brake test. The blue curve represents the sample prior to testing, with grain sizes predominantly below 20 µm. The orange curve corresponds to the tested sample, showing a shift toward larger grains between 30 and 60 µm. The grey box highlights the grain coarsening induced by thermomechanical stress during braking.
Figure 9. EBSD grain size distribution of the coating layers before and after the brake test. The blue curve represents the sample prior to testing, with grain sizes predominantly below 20 µm. The orange curve corresponds to the tested sample, showing a shift toward larger grains between 30 and 60 µm. The grey box highlights the grain coarsening induced by thermomechanical stress during braking.
Coatings 15 01106 g009
Coatings 15 01106 g010
Figure 10. EBSD mapping on analysis multi-layer laser deposited 316L alloy coating on GJL without the brake test, (a) texture, (b) pole figure.
Figure 10. EBSD mapping on analysis multi-layer laser deposited 316L alloy coating on GJL without the brake test, (a) texture, (b) pole figure.
Coatings 15 01106 g010
Coatings 15 01106 g011
Figure 11. EBSD mapping on analysis multi-layer laser deposited 316L alloy coating on GJL with the brake test, (a) texture, (b) pole figure.
Figure 11. EBSD mapping on analysis multi-layer laser deposited 316L alloy coating on GJL with the brake test, (a) texture, (b) pole figure.
Coatings 15 01106 g011
Coatings 15 01106 g012
Figure 12. Schematics for the competitive grain growth: (a1–a3) without brake test, showing textured grains with converging grain boundaries; and (b1–b3) after (with) brake test, showing diverging grain boundaries. Colored arrows indicate the direction of grain boundary movement (green: upward, yellow: lateral). The yellow dotted square highlights the region discussed in the main text, where significant microcrack formation and grain boundary modification is observed. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Figure 12. Schematics for the competitive grain growth: (a1–a3) without brake test, showing textured grains with converging grain boundaries; and (b1–b3) after (with) brake test, showing diverging grain boundaries. Colored arrows indicate the direction of grain boundary movement (green: upward, yellow: lateral). The yellow dotted square highlights the region discussed in the main text, where significant microcrack formation and grain boundary modification is observed. Note: The asterisk (*) next to the scale bar indicates that the scale was automatically generated by the ZEISS SEM system based on the magnification settings.
Coatings 15 01106 g012
Coatings 15 01106 g013
Figure 13. Mechanical properties of substrate and coating layers before and after the brake test, including microhardness (HV0.3, n = 9), Brinell hardness, and compression strength. The WC-reinforced layer shows the highest hardness.
Figure 13. Mechanical properties of substrate and coating layers before and after the brake test, including microhardness (HV0.3, n = 9), Brinell hardness, and compression strength. The WC-reinforced layer shows the highest hardness.
Coatings 15 01106 g013
Table 1. Chemical composition of the GJL substrate and the 316L powder.
Table 1. Chemical composition of the GJL substrate and the 316L powder.
Element [wt.%]GJL 150316L
C3.50 ± 0.10.01
Si2.00 ± 0.10.80
Mn0.60 ± 0.051.50
P<0.10 ± 0.02-
S<0.08 ± 0.02<0.01
Cu0.20 ± 0.020.00
Cr0.20 ± 0.0217.00
Mo0.35 ± 0.12.50
Ni<0.2012.00
Sn<0.10-
N--
FeBalanceBalance
Table 2. List of samples analyzed.
Table 2. List of samples analyzed.
SampleSubstrateFirst LayerSecond LayerHard ParticlesSample Condition
1----Powder 316L
2GJL316L316LSpherical WCwithout brake shock corrosion test
3GJL316L316LSpherical WCwith brake shock corrosion test
Table 3. Summary of measured mechanical properties of the substrate and coating layers. Microhardness (HV0.3) and Brinell hardness (HBW) were each measured nine times. Tensile strength (Rm) of the substrate was estimated from wedge compression tests according to VDG340.
Table 3. Summary of measured mechanical properties of the substrate and coating layers. Microhardness (HV0.3) and Brinell hardness (HBW) were each measured nine times. Tensile strength (Rm) of the substrate was estimated from wedge compression tests according to VDG340.
Sample(S)_Position: MaterialHardness
HV 0.3		Standard DeviationHardness
HBW 5/750		Standard
Deviation		Wedge Compression Strength Rm (MPa)Standard
Deviation
S2_Substrate: GJL2441617981393
S3_Substrate: GJL2451618481433
S2_First coating layer: 316L2327
S3_First coating layer: 316L2237
S2_Second coating layer: 316L _WC47830
S3_Second coating layer: 316L _WC 43230
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Masafi, M.; Conzelmann, A.; Palkowski, H.; Mozaffari-Jovein, H. Microstructure Development of a Functionalized Multilayer Coating System of 316L Austenitic Steel on Grey Cast Iron Under Braking Force in a Corrosive Environment. Coatings 2025, 15, 1106. https://doi.org/10.3390/coatings15091106

AMA Style

Masafi M, Conzelmann A, Palkowski H, Mozaffari-Jovein H. Microstructure Development of a Functionalized Multilayer Coating System of 316L Austenitic Steel on Grey Cast Iron Under Braking Force in a Corrosive Environment. Coatings. 2025; 15(9):1106. https://doi.org/10.3390/coatings15091106

Chicago/Turabian Style

Masafi, Mohammad, Achim Conzelmann, Heinz Palkowski, and Hadi Mozaffari-Jovein. 2025. "Microstructure Development of a Functionalized Multilayer Coating System of 316L Austenitic Steel on Grey Cast Iron Under Braking Force in a Corrosive Environment" Coatings 15, no. 9: 1106. https://doi.org/10.3390/coatings15091106

APA Style

Masafi, M., Conzelmann, A., Palkowski, H., & Mozaffari-Jovein, H. (2025). Microstructure Development of a Functionalized Multilayer Coating System of 316L Austenitic Steel on Grey Cast Iron Under Braking Force in a Corrosive Environment. Coatings, 15(9), 1106. https://doi.org/10.3390/coatings15091106

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop