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Article

Investigation of the Wear Resistance of Hard Anodic Al2O3/IF-WS2 Coatings Deposited on Aluminium Alloys

by
Joanna Korzekwa
1,*,
Adam Jarząbek
1,
Marek Bara
1,
Mateusz Niedźwiedź
1,
Krzysztof Cwynar
2 and
Dariusz Oleszak
3,*
1
Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pułku Piechoty 1a, 41-500 Chorzów, Poland
2
Institute of Chemistry, Faculty of Science and Technology, University of Silesia in Katowice, Szkolna 9, 40-006 Katowice, Poland
3
Faculty of Materials Science and Engineering, Warsaw University of Technology, 02-507 Warsaw, Poland
*
Authors to whom correspondence should be addressed.
Materials 2025, 18(15), 3471; https://doi.org/10.3390/ma18153471
Submission received: 16 June 2025 / Revised: 14 July 2025 / Accepted: 22 July 2025 / Published: 24 July 2025
(This article belongs to the Special Issue Surface Engineering in Materials (2nd Edition))
Browse Figures
Versions Notes

Abstract

The anodic oxide layer’s porosity is considered a functional feature, acting as a reservoir of lubricants. This feature enables the design of self-lubricating systems that effectively reduce friction and wear. To improve the tribological performance of Al2O3 anodic coatings on EN AW 5251 aluminium alloys, this paper presents a modification of the coating with tungsten disulfide (IF-WS2) nanopowder and its effect on coating resistance. The wear properties of Al2O3/IF-WS2 coatings in contact with a cast iron pin were investigated. The results include the analysis of the friction coefficient in the reciprocating motion without oil lubrication at two loads, the analysis of the wear intensity of the cast iron pin, the characterisation of wear scars, and the analysis of SGP parameters. Two-level factorial analysis showed that load and nanomodification significantly affected the load-bearing parameter Rk. Incorporation of the modifier, especially under higher loads, reduced the Rk value, thus improving the tribological durability of the contact pair. Both load and nanomodification had a notable impact on the coefficient of friction. The use of IF-WS2-modified coatings reduced the coefficient, and higher loads further enhanced this effect, by approximately 9% at a load of 0.3 MPa and 15% at a load of 0.6 MPa, indicating improved lubricating conditions under greater contact stress.

1. Introduction

High-strength aluminium alloys are widely employed in structural and mechanical applications where low weight and high mechanical performance are critical, notably in the automotive, aerospace, and machinery sectors [1,2]. Their favourable strength-to-weight ratio and corrosion resistance make them attractive for components subjected to dynamic loading and environmental exposure. However, under conditions involving sliding contact, aluminium alloys are inherently prone to adhesive wear and galling due to their relatively low surface hardness and high chemical reactivity. This limitation poses a significant challenge for components operating under frictional conditions, where surface degradation can lead to reduced performance and shortened service life.
Among the well-known methods are mechanical techniques, such as Ultrasonic Nanocrystalline Surface Modification (UNSM), which enable the formation of strain-hardened surface layers on aluminium alloy surfaces to enhance their mechanical properties [3,4]. Surface texturing, also classified as a mechanical technique, combined with using solid lubricants, has also significantly demonstrated the ability to reduce friction and wear under dry sliding conditions [5,6,7]. Chen et al. demonstrated microtexturing of aluminium alloy surfaces in combination with anodising and solid lubricants. [8]. In recent decades, significant research efforts have also been directed toward developing modifications that utilise anodising in combination with solid lubricants [9,10,11,12], metal–organic frameworks (MOFs) [13], or layered double hydroxide (LDH) conversion coatings [9,14,15] to protect metals against corrosion and/or enhance the tribological performance of anodic coatings formed on aluminum alloys. Anodising continues to be a widely used and easily scalable process in industrial applications, especially when compared to precision laser equipment, which may present greater challenges when applied to large surface areas or components with complex geometries.
The mechanical and tribological properties of the oxide coating produced during the anodising process are strongly influenced by the surface condition, porosity, and thickness of the Al2O3 layer. These, in turn, are highly dependent on the anodising conditions, such as voltage, temperature, and electrolyte composition [16,17,18]. The porosity of anodic oxide layers is considered a functional feature that is capable of acting as a reservoir for lubricants. This characteristic enables the design of self-lubricating systems that effectively reduce friction and wear [19,20,21].
Tribological wear tests of material pairs under dry (unlubricated) conditions are crucial for ensuring mechanical systems’ reliability, durability, and efficiency, especially in applications where lubricating oil is not feasible. Fundamental studies on oxide coatings formed on aluminium alloys support the selection of material pairs that exhibit the lowest wear rates and the highest durability under specific conditions. These investigations also help determine how long such coatings effectively protect the substrate and under what conditions they begin to degrade. Kim et al. [22] conducted tribological tests on nanoporous anodic aluminium oxide (AAO) coatings with varying pore sizes in sliding contact with a steel ball, under normal loads ranging from 1 mN to 1 N. The results showed that larger pore sizes corresponded to higher coefficients of friction. Additionally, it was observed that the coefficient of friction significantly decreased with increasing load for all AAO layers, regardless of their pore size. Hu et al. [23] conducted tribological tests on AAO coatings embedded with C60 nanoparticles, using a GCr15 bearing steel pin in reciprocating motion under dry friction conditions and a normal load of 5 N. They found that appropriate treatment to enlarge the nanopores of the AAO coating, combined with incorporating C60 particles, effectively reduced the coefficient of friction between the tested pair. Moreover, the modified AAO coating demonstrated good wear resistance. Lee et al. [24], in ball-on-disc sliding wear tests using a bearing steel ball and a PAA (porous anodic alumina)-coated disc, observed that water penetrating the pores is released onto the surface through elastic–plastic deformation. This released water acts as a lubricating film, which minimises direct contact between the surfaces and thereby reduces the coefficient of friction. In the study by Takaya et al. [25], friction measurements were carried out in a rotating ball-on-disc configuration, using a bearing steel ball and an AAO coating impregnated with PVP-iodine. It was found that the modified AAO coating exhibited a lower coefficient of friction and greater durability compared to the non-impregnated AAO coating. Maejima et al. [26] conducted friction measurements using a ring-on-disc (hardened steel ring-disc) and ball-on-disc (WC-Co ball-disc) configuration. The disc consisted of an AAO coating impregnated with molybdenum sulfide compounds. Both impregnated and non-impregnated samples were compared. It was found that the particle size of the solid lubricants was larger than the pore size of the AAO films, preventing direct impregnation of the lubricant powder into the pores. Nevertheless, it was confirmed that molybdenum sulfide and related compounds impregnated the AAO structure through the pore bases, significantly reducing friction and improving the running-in behaviour compared to the unmodified coating. Tao et al. [27] conducted friction and wear tests using a ball-on-disc tribometer, with a steel ball and an AAO disc modified with MoS2, under a load of 5 N. They found that MoS2 particles transferred during friction reduced the coefficient of friction until they were completely depleted. However, not all MoS2 particles present in the pores could be easily delivered to the contact interface. As a result, once the available MoS2 was exhausted, the friction between the AAO layer and the steel ball increased. The amount of MoS2 reaching the sliding interface was insufficient to form a continuous lubricating film between the surfaces. Nonetheless, it was confirmed that the MoS2 present within the pores of the oxide layer contributed to a reduction in the wear of the steel ball. Skeldon, Wang, and Thompson [10,28] found that a hard-anodic coating, combined with an incorporated solid lubricant like MoS2, MoS3, and S, can significantly enhance the tribological properties of aluminium compared to a conventional porous aluminium oxide layer. Their studies demonstrated that the introduced solid lubricant reduced the wear rate of aluminium in tribological contact with a steel pin.
Lubricated conditions significantly reduce friction and wear by forming a protective film between contacting surfaces. However, in many practical applications—such as in aerospace, automotive, or precision mechanical systems—lubrication may be limited, intermittent, or even undesirable due to design, environmental, or maintenance constraints. Materials and coatings must provide reliable tribological performance under dry conditions in such cases. Therefore, evaluating the effectiveness of IF-WS2-modified Al2O3 coatings in dry sliding is essential for understanding their suitability for these demanding environments, where conventional lubrication cannot be applied.
This work builds on our previous studies of the same coating system [29], where detailed structural and compositional analyses (including EDS) confirmed the successful incorporation and distribution of IF-WS2 nanoparticles; the current study focuses specifically on the tribological behaviour of the coating. The primary objective of this study is to investigate the influence of normal load and IF-WS2 modification on the wear behaviour of an Al2O3 coating applied to an EN-AW 5251 aluminium alloy in combination with ductile iron. The operating conditions modelled in this study simulate dry, reciprocating sliding contact between Al2O3 and Al2O3/IF-WS2 coatings and a ductile iron counter-body. These conditions represent tribological contacts found in lightweight mechanical systems, such as sliding elements in automotive, aerospace, and industrial equipment, where lubrication is limited or not feasible. The expected scientific contribution lies in determining whether IF-WS2 nanoparticles act as effective solid lubricants when embedded in Al2O3 coatings and whether this effect depends on the applied load. The worn surfaces were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Based on statistical analysis, the results include a comprehensive evaluation of the coefficient of friction, wear intensity, and surface geometric parameters (SGPs). Due to the lack of available literature on this specific material combination (Al2O3/IF-WS2 coatings versus ductile iron pins), our findings provide novel data for solid lubrication and wear-resistant coatings. The paper uses statistical methods applied to DOE (Design of Experiments) design and analysis, which are helpful for process optimisation and finding relationships between input variables and measured parameters. DOE methodology is described in the studies [30,31,32]. However, to the authors’ knowledge, such a study has not yet been reported for tribological studies between cast iron pins and IF-WS2 modified oxide coatings on aluminium.

2. Materials and Methods

2.1. Sample Preparation

The investigated material was a composite oxide film consisting of Al2O3 and IF-WS2, fabricated through a two-step process. In the first stage, a graded Al2O3 coating was formed on the EN AW-5251 aluminium alloy via electrochemical oxidation in a ternary acid solution comprising sulfuric, oxalic, and phthalic acids (Avantor Performance Materials Poland S.A., Gliwice, Poland). Before anodisation, the samples underwent sequential etching in aqueous solutions of KOH and HNO3 (both from Avantor Performance Materials Poland S.A., Gliwice, Poland). Hard anodisation was carried out at a charge density of 180 A·min/dm2, under conditions of controlled current density, fixed duration, and a constant electrolyte temperature of 303 ± 1 K. In the second stage, IF-WS2 nanoparticles (NPs; NanoMaterials Ltd., Yavne, Israel) were introduced into the porous alumina layer. In Table 1, the sonication parameters are presented. The anodised specimens were immersed in room temperature ethanol containing 15 g/L of IF-WS2 NPs, subjected to ultrasonication at 20 kHz with a total energy input of 10 kJ for 5 min using a VCX 130 sonicator (Sonics & Materials Inc., Newtown, CT, USA), and subsequently left undisturbed for 24 h to facilitate nanoparticle incorporation [29].

2.2. Research Methods

To investigate the composition of nanoscale Al2O3 fibres incorporating self-organised IF-WS2 nanoparticles (NPs), the prepared samples were examined using a HITACHI S-4700 scanning electron microscope (SEM) (Hitachi High-Tech Corporation, Tokyo, Japan) equipped with a NORAN Vantage digital energy-dispersive X-ray spectroscopy (EDS) system (NORAN Instruments, Inc., Middleton, WI, USA). The surface and cross-sectional morphology of the Al2O3/IF-WS2 NP coatings was analysed in backscattered electron (BSE) mode using an yttrium aluminium garnet (YAG) detector (Hitachi High-Tech Corporation, Tokyo, Japan). A YAG single crystal was employed to reduce the electron dose and minimise beam-induced artefacts. Cross-sectional observations were performed on freshly fractured specimens. Before imaging, a thin carbon film was sputter-coated onto the sample surfaces to enhance contrast and reduce charging effects during SEM analysis. Microscopic observations of the ductile iron and Al2O3/IF-WS2 with wear track were conducted using a scanning electron microscope (SEM) with EDS JEOL 6480 (JEOL, Ltd., Tokyo, Japan). A Samsung Galaxy A32 mobile phone camera (Samsung Electronics, Suwon, Republic of Korea) was used for macroscopic imaging.
The coating thickness was measured using a contact method with the Fischer Dualoscope MP40 device (Helmut Fischer GmbH + Co. KG, Sindelfingen, Germany). The instrument operates based on the eddy current method. Ten measurements were performed on the surface of each sample, and the results were used to calculate the mean coating thickness along with the corresponding standard deviations.
Amplitude parameters, Abbott–Firestone bearing curves, and surface roughness profiles were determined based on profilometric measurements conducted before and after the tribological test. The measurements were performed using a Form TalySurf Series 2.50i contact profilometer (Taylor Hobson Ltd., Leicester, UK).
The samples prepared as described were subjected to tribological testing using a T-17 tribotester (Łukasiewicz Research Network—Institute for Sustainable Technologies, Radom, Poland). The tests were conducted in a pin-on-plate configuration under reciprocating motion at room temperature and a relative humidity of 40% ± 10%. An average sliding speed of 0.2 m/s was maintained, corresponding to an operating frequency of 2.5 Hz. All tests were performed under dry friction conditions. Tribological tests were conducted under loads of 0.3 MPa (~19N) and 0.6 MPa (~38N). The total sliding distance for each tribological pair was 1 km. A ductile iron pin with a diameter of 9 mm was employed as the counter-sample. The tests yielded frictional characteristics, including friction force data. The average coefficient of friction was calculated based on the stabilised regions of the friction force profile. Before each dry friction test, the ductile iron pin was lapped using P1000-grade sandpaper (Union Abrasives, Inc., Pepperell, MA, USA) for 10 min under a constant load of 3.242 kg. This procedure ensured uniform surface roughness of the counter-sample, thereby standardising the initial conditions across all test runs. The wear of the ductile iron pin was evaluated by measuring its mass before and after each test cycle using a WPA-60G analytical balance (Radwag, Radom, Poland) with a precision of ±0.1 mg.
A 2k factorial design experiment with replication was conducted using Statistica v. 13 software (TIBCO Software Inc., Palo Alto, CA, USA) to evaluate the influence of input parameters on the dependent variables (Table 2). The independent variables were those doped with IF-WS2 or undoped Al2O3 coating and load (0.3 or 0.6 MPa). The dependent variables for wear resistance properties were structural geometric parameters (SGPs), friction coefficient μ, and the intensity of pin wear.

3. Results and Discussion

As a result of the electrochemical process, oxide coatings with the thicknesses presented in Figure 1 were obtained. The application of ultrasound in a sonicator enabled the deagglomeration of the IF-WS2 nanopowder and, in combination with a 24 h sedimentation method, facilitated its incorporation into the nanoporous structure of the Al2O3 coating (Figure 2). Photo 2a shows the IF-WS2 nanopowder introduced between Al2O3 nanofibers on the coating of the fresh fracture. Photo 2b shows the IF-WS2 nanopowder nested in the macropores on the Al2O3 coating surface.
Figure 3a shows an example of a friction pair: oxide coating–cast iron pin. Figure 3b shows a photo of the oxide coating with a visible wear track resulting from interaction with a cast iron pin. Friction traces on unmodified Al2O3 oxide coatings are shown on samples 1–4, and modified Al2O3/IF-WS2 oxide coatings are shown on samples 5–8. Figure 3b shows a noticeable difference in the deposited cast iron film between the unmodified and modified samples. The transfer film on the modified Al2O3/IF-WS2 coatings appears thinner overall (adhesive wear), with more frequent occurrences of isolated, thicker regions of deposited cast iron (abrasive wear) than the unmodified Al2O3 coatings. In the case of unmodified Al2O3 coatings, in addition to the friction traces, a cycling tacking of the pin material (parallel marks) was observed on the coating surface, which may correspond to coating cracks. Such traces were not observed on the modified Al2O3/IF-WS2 coating surface. Similar coating distortions were observed in [33], where coatings without cracks were more wear resistant. What should be emphasised, however, regardless of whether the Al2O3 coatings were modified or not, the coatings were not broken after friction, and a well-adhering sliding film formed from the wear products of the cast iron pin remained on their surface. The adhesive bonds observed in some cases in the tribofilm are richer in iron, which suggests a thicker sliding film in these places. In the unmodified Al2O3 coatings, repetitive parallel marks were observed after the tribological interaction, which are indicative of adhesive wear from the ductile iron counter-body and are likely associated with microcracks in the Al2O3 coatings. These marks were not observed in the Al2O3/IF-WS2 coatings, suggesting a change in the wear mechanism. The presence of IF-WS2 nanoparticles, known for their solid lubrication properties, likely reduced the coefficient of friction and localised stresses at the contact interface. This, in turn, minimised the extent of parallel adhesive interactions and prevented crack formation.
Figure 4 shows an image of the cast iron pin used in the friction tests, accompanied by SEM images of the etched surface and EDS analysis of the selected areas.
Figure 5 and Figure 6 show images of the wear tracks, SEM images of the wear tracks, and EDS analysis of the selected areas. As observed on both the unmodified Al2O3 and modified Al2O3/IF-WS2 coatings, a transfer film from the counter-face was deposited (Figure 5 and Figure 6a), which was identified as spheroidal cast iron through EDS analysis (Figure 5c and Figure 6c,e). In areas where thicker deposits were visible on the Al2O3 coatings, increased intensity of the iron reflection characteristic of the spheroidal cast iron was recorded, confirming the presence of a thicker transfer film at these locations.
The following parameters were selected to analyse the influence of the additive and applied load on surface geometric parameters (SGP): Rq, Rk, Rvk, Rpk, and Rsk. The Rq parameter, representing the root mean square deviation of the surface profile, is particularly sensitive to larger surface irregularities. It is commonly used in tribological studies and recommended when it is essential to accounting for peaks and valleys in greater detail. Surface roughness significantly affects the contact area between interacting surfaces—higher Rq values indicate a rougher surface, which may increase friction or alter the wear mechanism. Roughness also plays a role in lubricant retention—microvalleys can trap lubricant, thereby enhancing tribological performance. Conversely, depending on material type and operating conditions, lower Rq values may lead to reduced wear depending on material type and operating conditions. In nanolubricant deposition, surface valleys are significant in the present study. Pareto and marginal mean charts were used to analyse the results. The most commonly used significance level of 0.05 (5%) was used in the presented studies. The significance level and confidence intervals are closely related by the relationship (1 − α = 0.95). This means that there is a 95% chance that the confidence interval will include the actual values of the parameter. In Pareto charts, the horizontal axis shows the normalised effect values (absolute values), while the vertical line indicates the statistical significance threshold at p = 0.05. Factors on this line’s right side are considered statistically significant. As shown in Figure 7a, within the adopted experimental design, only the applied load significantly influenced the Rq parameter. Specifically, lower Rq values were observed under higher load conditions (0.6 MPa), as illustrated in Figure 7b. This suggests that roughness is sensitive to mechanical loading, reflecting intensified wear. Based on Figure 8, and considering the measurement uncertainty, it can be assumed that the initial surface roughness Rq of both unmodified Al2O3 and modified Al2O3/IF-WS2 coatings was similar, approximately 0.7 µm before the tribological tests and 0.5 µm (0.3 MPa load) and 0.43 µm (0.6 MPa load) after the tests. The decrease in Rq observed after the tribological tests indicates a typical smoothing of the friction surfaces, resulting from deformation and partial shearing of the Al2O3 coating asperities, as well as the filling of surface valleys with wear debris originating from cast iron. An increase in load intensifies these mechanisms—higher contact pressure leads to deeper deformation and greater removal of material from surface asperities, which results in a more pronounced reduction in the Rq parameter. The absence of significant changes in Rq due to IF-WS2 modification indicates that the additive did not strongly affect the surface topography in terms of measurable roughness, despite influencing the friction behaviour.
The Rk parameter, derived from the Abbott–Firestone bearing curve (also known as the material ratio curve), belongs—along with Rpk and Rvk—to the roughness parameters defined in ISO 21920-2 [34]. These parameters provide a more comprehensive interpretation of the microtopography of a surface. Rk represents the core roughness depth, corresponding to the portion of the surface profile that primarily carries the load during contact—it reflects the main load-bearing capacity of the surface.
Analysis of the two-level factorial experimental design revealed that the Rk parameter is significantly influenced by both surface modification and applied load (Figure 9a). At a load of 0.3 MPa, a reduction of approximately 23% in the Rk value was observed for the modified Al2O3/IF-WS2 coating compared to the unmodified Al2O3 coating (Figure 9b). Additionally, compared with the initial (pre-test) Rk values, a decrease in Rk was noted for both the unmodified and modified coatings after the tribological tests (Figure 10). Modification did not significantly affect the Rk parameter under the higher load condition (0.6 MPa). Incorporating the IF-WS2 nanomodifier into Al2O3 coatings positively affects the load-bearing zone by reducing the Rk value, which may enhance the tribological durability of the tested material pairings under 0.3 MPa load. However, at 0.6 MPa, modification appears to have no significant influence.
The Rvk parameter defines the depth of valleys capable of retaining lubricant. According to the statistical analysis, Rvk is influenced solely by the applied load during the tribological test (Figure 11a). At a lower load of 0.3 MPa (Figure 11b), more surface valleys are preserved—these features are inherent to the structure of the anodised coating. As the applied load increases to 0.6 MPa, more valleys are lost—the surface becomes flattened and more uniform. This effect results from the mechanical flattening of the Al2O3 coating surface under the load applied by the pin and the filling or smoothing of surface valleys with material from the pin itself, which in this study was made of spheroidal graphite cast iron.
As shown in Figure 12, the Rvk parameter decreases after the tribological tests compared to the surface condition before testing.
The third parameter derived from the Abbott–Firestone bearing curve, Rpk, was unaffected by either surface modification or the applied load. Therefore, Figure 13a presents only the changes in this parameter following the tribological tests, compared to the pre-test values. In both cases, Rpk increased after testing. Rpk characterises the easily removable surface peaks that typically wear off during the initial stages of contact. It is generally expected to decrease after tribological interaction. However, in this study, an increase was observed. This phenomenon is attributed to the formation of a transferred cast iron sliding film, which protrudes above the functional surface—these are adhesive junctions or transfer layers resulting from material transfer from the cast iron pin. Similar observations were made for the Rsk parameter, which describes the asymmetry (skewness) of the surface profile and was likewise found to be independent of the input variables examined (Figure 13b). A negative Rsk value indicates a surface dominated by valleys, which can enhance lubricant retention and reduce friction but may also reduce the load-bearing capacity. Based on average values (without accounting for standard deviation), it was noted that increasing the load raised the skewness coefficient, thereby reducing the surface’s capacity to retain lubricant.
Figure 14 presents a 3D visualisation of the Al2O3 oxide coatings: Figure 14a shows the coating surface before the tribological test, and Figure 14b,d,f,h depict the unmodified Al2O3 coatings after testing for samples 1, 2, 3, and 4, respectively. Figure 14c,e,g,i illustrate the modified Al2O3/IF-WS2 coatings after testing for samples 5, 6, 7, and 8, respectively. The surface before friction (Figure 14a) is characterised by a uniform topography with minor height differences, mainly in the 1–2.5 µm range, locally up to 4 µm. The natural roughness results from the coating manufacturing process. In each case of the 3D image shown, parallel bands characteristic of sliding contact resulting from abrasive wear are visible. The significantly increased intensity of the yellow, green, and red colours suggests local deformations and microcracks. The material peaks marked in white suggest cast iron material transfer (adhesion). After friction, all surfaces show a slight degree of wear, with small surface deformation. Observation of the 3D surface images revealed that the surface profile of the Al2O3 coatings—both unmodified and modified—exhibited only minor deformation in the texture as a result of interaction with the cast iron pin.
As shown in the Pareto and marginal means charts (Figure 15a,b, respectively), neither the surface modification nor the applied load had a statistically significant effect on the wear intensity of the cast iron pin.
Figure 16 illustrates the friction coefficient as a function of time for all tested samples. According to the Pareto chart (Figure 17a), both the applied load and the surface modification had a statistically significant impact on the friction coefficient, with the load having a more pronounced effect. As shown in Figure 17b, the friction coefficient was lower for Al2O3 coatings doped with the IF-WS2 nanolubricant, by approximately 9% at a load of 0.3 MPa and 15% at a load of 0.6 MPa. It can be hypothesised that at the lower load of 0.3 MPa, a greater number of valleys—originating from the anodised coating structure—remain intact (see Figure 11b), which limits the interaction of the loosely embedded IF-WS2 nanolubricant with the load-bearing surface area. In contrast, under higher load conditions, the lubricating effect of the additive is enhanced due to the disruption of Van der Waals forces. The fullerene-like structure of IF-WS2 breaks down, forming 2H-WS2 lamellae, which facilitate sliding. Additionally, the cast iron transfer film becomes enriched with these 2H-WS2 planes, further contributing to the observed reduction in the friction coefficient.
Although a reduction in friction coefficient is often expected to correspond with lower wear, this relationship is not universal—wear is governed by many factors: hardness, microstructural integrity, the presence of tribochemical layers, and rough surface features. According to Zhou et al. [35], hardness often plays a more significant role in determining wear rate than friction coefficient, especially in PVD coatings. As stated by Krella [36], a decrease in the coefficient of friction is often associated with a reduction in wear rate; however, no consistent correlation between these two parameters has been established. Moreover, some studies have reported cases where an increase in the coefficient of friction coincided with a reduction in wear rate, indicating that a low friction coefficient does not necessarily imply improved wear resistance. In our case, the applied IF-WS2 modification altered frictional behaviour—likely through changes in surface interactions or tribofilm formation—but did not significantly affect material properties such as hardness, structural integrity, or tribochemical stability. WS2 belongs to the transition metal dichalcogenides, part of a large class of so-called two-dimensional or layered materials. Within the layers, the atoms are bonded by strong covalent forces, while van der Waals forces hold together the individual layers. WS2, due to its layered structure and the weak van der Waals interactions between the layers, causes a reduction in the coefficient of friction through a peeling mechanism [37]. In the case of the fullerene-like IF-WS2 consisting of dozens of cage-like concentric layers [38], loading causes exfoliation of the outer layers of the nanoparticle, inducing slippage and a reduction in the coefficient of friction. Our results indicated that the addition of IF-WS2 does not influence the morphology of the coating, thereby not affecting its hardness and wear resistance. Furthermore, the addition of IF-WS2 does not affect the materials’ properties, such as hardness, the structural integrity of Al2O3 nanofibers, or tribochemical stability. Therefore, the absence of wear rate change is consistent with known tribological principles whereby these dominant factors more strongly control wear resistance than friction alone.
The present study demonstrates that modifying Al2O3 coatings with IF/WS2 nanopowder led to a moderate improvement in frictional behaviour when tested against a ductile iron counter-body. This limited enhancement may be attributed to the likely non-uniform distribution of IF/WS2 nanoparticles within the ceramic matrix. This aspect warrants further investigation and optimisation of the deposition process. Although ductile iron is not typically used in tribological studies involving Al2O3 coatings, its selection was intentional, aiming to replicate specific industrial conditions characterised by dry sliding contacts in lightweight mechanical systems. The adhesive wear mechanisms observed on the cast iron surface support the relevance of this material pairing. Future research should explore their tribological performance under varying environmental conditions, including elevated humidity and temperature fluctuations, which more accurately reflect real-world operational environments, to assess the functional potential of such coatings fully.

4. Conclusions

To investigate the potential application of IF-WS2 nanoparticles (NPs) in Al2O3 coatings for tribological studies involving spheroidal graphite cast iron, an Al2O3 coating embedded with IF-WS2 nanoparticles was fabricated using a sonication-assisted sedimentation technique. The effectiveness of this approach was evaluated through SEM analysis, surface geometric parameter (SGP) measurements, friction coefficient monitoring, and cast iron pin wear assessment. The main conclusions drawn from the study are as follows:
  • SEM/EDS analysis confirmed the transfer of pin material onto the fabricated Al2O3 coatings. In some cases, adhesive junctions were observed, with localised accumulations of transferred spheroidal graphite iron.
  • Three-dimensional surface imaging revealed that the unmodified and IF-WS2-modified Al2O3 coatings exhibited minor subsurface deformation due to sliding contact with the cast iron pin.
  • In the analysed test setup, the applied load significantly influenced the Rq roughness parameter, while the IF-WS2 nanomodifier did not considerably affect surface roughness. This suggests that load conditions are more critical than material modification in the context of improving roughness (and potentially friction).
  • The two-level factorial analysis demonstrated that modification and load significantly influenced the Rk load-bearing parameter. Incorporating the nanomodifier and increased load enhanced the load-bearing capacity of the surface by reducing the Rk value, thereby improving the tribological durability of the tested pairs.
  • The Rvk parameter, related to valley depth for lubricant retention, depended solely on the load—lower loads helped preserve valleys within the coating structure. In contrast, higher loads led to valley reduction due to surface flattening and filling with pin material.
  • Parameters Rpk (reduced peak height) and Rsk (profile skewness) showed no significant dependency on the input variables. However, higher loads increased Rpk, and the negative Rsk values indicated a valley-dominant surface morphology, which can enhance lubricant retention and reduce friction, albeit potentially at the expense of load-bearing capacity.
  • Neither modification nor load significantly influenced the wear intensity of the cast iron pin.
  • Both load and modification had a notable effect on the friction coefficient. The use of IF-WS2-modified Al2O3 coatings reduced the friction coefficient, and the coefficient also decreased with increasing load, by approximately 9% at a load of 0.3 MPa and 15% at a load of 0.6 MPa, suggesting enhanced lubricating performance under higher contact stress.

Author Contributions

Conceptualization, J.K., M.N. and M.B.; methodology, J.K., A.J. and K.C.; software, J.K.; formal analysis, J.K. and M.B.; investigation, J.K., and A.J.; writing—original draft preparation, J.K. and M.N.; writing—review and editing, J.K. and M.B.; visualization, J.K.; supervision, D.O. 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.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Acknowledgments

The authors gratefully acknowledge Marzena Dzida for providing the sonicator lab and Sławomir Kaptacz for profilometric measurements. Checking the correctness of the English language (Grammarly (v1.2.175.1706) and ChatGPT (4-turbo, https://chatgpt.com; 16 June 2025).

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Davis, J.R. Aluminum and Aluminum Alloys. Alloy. Underst. Basics 2001, 351–416. [Google Scholar] [CrossRef]
  2. Runge, J.M. The Metallurgy of Anodizing Aluminum: Connecting Science to Practice; Springer International Publishing: Cham, Switzerland, 2018; ISBN 9783319721774. [Google Scholar]
  3. Oh, J.; Park, H.D.; Gwak, M.; Lee, J.; Son, S.; Amanov, A.; Kim, H.S.; Seol, J.B.; Sung, H.; Kim, J.G. Mechanical Property Enhancement in Gradient Structured Aluminum Alloy by Ultrasonic Nanocrystalline Surface Modification. Mater. Sci. Eng. A 2021, 812, 141101. [Google Scholar] [CrossRef]
  4. Efe, Y.; Karademir, I.; Husem, F.; Maleki, E.; Karimbaev, R.; Amanov, A.; Unal, O. Enhancement in Microstructural and Mechanical Performance of AA7075 Aluminum Alloy via Severe Shot Peening and Ultrasonic Nanocrystal Surface Modification. Appl. Surf. Sci. 2020, 528, 146922. [Google Scholar] [CrossRef]
  5. Rosenkranz, A.; Costa, H.L.; Baykara, M.Z.; Martini, A. Synergetic Effects of Surface Texturing and Solid Lubricants to Tailor Friction and Wear—A Review. Tribol. Int. 2021, 155, 106792. [Google Scholar] [CrossRef]
  6. Betts, J.C. Laser Surface Modification of Aluminium and Magnesium Alloys. In Surface Engineering of Light Alloys: Aluminium, Magnesium and Titanium Alloys; Hanshan, D., Ed.; Woodhead Publishing: Cambridge, UK, 2010; pp. 444–474. [Google Scholar] [CrossRef]
  7. Huang, Q.; Shi, X.; Xue, Y.; Zhang, K.; Wu, C. Recent Progress on Surface Texturing and Solid Lubricants in Tribology: Designs, Properties, and Mechanisms. Mater. Today Commun. 2023, 35, 105854. [Google Scholar] [CrossRef]
  8. Chen, L.; Liu, Z.; Shen, Q. Enhancing Tribological Performance by Anodizing Micro-Textured Surfaces with Nano-MoS2 Coatings Prepared on Aluminum-Silicon Alloys. Tribol. Int. 2018, 122, 84–95. [Google Scholar] [CrossRef]
  9. Nie, C.; Cao, F.; Zhu, T.; Sun, Z.; Wang, D.; Wu, Y.; Ying, L. Study on the Tribological Properties and Corrosion Resistance of the In-Situ Grown Zn–Al-LDHs Film on Anodic Aluminum Surface. Mater. Sci. Eng. B 2023, 297, 116751. [Google Scholar] [CrossRef]
  10. Skeldon, P.; Wang, H.W.; Thompson, G.E. Formation and Characterization of Self-Lubricating MoS2 Precursor Films on Anodized Aluminium. Wear 1997, 206, 187–196. [Google Scholar] [CrossRef]
  11. Kumar, N.; Sharma, A.; Manoj, M.K.; Ahn, B. Taguchi Optimization of Tribological Properties and Corrosion Behavior of Self-Lubricating Al–Mg–Si/MoS2 Composite Processed by Powder Metallurgy. J. Mater. Res. Technol. 2023, 26, 1185–1197. [Google Scholar] [CrossRef]
  12. Kim, T.; Cho, H.; Choi, S.T.; Nam, W.; Lee, S.; Liang, H.; Kim, S. Controlled Deposition of Graphene Oxide on an Anodic Aluminum Oxide Substrate via Coffee-Ring Effect. J. Alloys Compd. 2023, 958, 170464. [Google Scholar] [CrossRef]
  13. Xiong, Z.; Zhang, W.; jin, S.; Wu, R.; Ma, F.; Wang, X.; Wang, G. One-Step Hydrothermal Fabrication of Co-MOFs/LDH Superhydrophobic Composite Coating with Corrosion Resistance and Wear Resistance on Anodic Aluminum Oxide. Appl. Surf. Sci. 2024, 677, 161023. [Google Scholar] [CrossRef]
  14. Stephan, J.; Kasneryk, V.; Serdechnova, M.; Scharnagl, N.; Gazenbiller, E.; Vaghefinazari, B.; Volovitch, P.; Starykevich, M.; Blawert, C.; Zheludkevich, M.L. Formation of Li-Al LDH Conversion Layer on AA2024 Alloy for Corrosion Protection. Appl. Surf. Sci. 2024, 659, 159919. [Google Scholar] [CrossRef]
  15. Xiong, Z.; Qi, Z.; Zhang, W.; Ji, M.; Ma, F.; Ying, L.; Wang, G. Enhancing Frictional and Corrosion Resistance Performance in Aluminum Alloy through in Situ Growth of NiZnAl-LDH Membrane and Its Modification. Surf. Interfaces 2024, 46, 104103. [Google Scholar] [CrossRef]
  16. Aerts, T.; Dimogerontakis, T.; De Graeve, I.; Fransaer, J.; Terryn, H. Influence of the Anodizing Temperature on the Porosity and the Mechanical Properties of the Porous Anodic Oxide Film. Surf. Coatings Technol. 2007, 201, 7310–7317. [Google Scholar] [CrossRef]
  17. Dervishi, E.; McBride, M.; Edwards, R.; Gutierrez, M.; Li, N.; Buntyn, R.; Hooks, D.E. Mechanical and Tribological Properties of Anodic Al Coatings as a Function of Anodizing Conditions. Surf. Coatings Technol. 2022, 444, 128652. [Google Scholar] [CrossRef]
  18. Kchaou, M. Friction Behavior of Anodic Oxide Layer Coating on 2017A T4 Aluminum Alloy under Severe Friction Solicitation: The Effect of Anodizing Parameters. Eng. Technol. Appl. Sci. Res. 2024, 14, 12574–12580. [Google Scholar] [CrossRef]
  19. Liu, Y.C.; Chen, Y.F.; Lin, Y.C.; Zheng, Y.H.; Lee, L.R.; Chang, M.H.; Ho, J.H.; Lin, Y.L.; Chen, J.T. Tailoring Nanopore Geometry in Anodic Aluminum Oxide Membranes through Physical Stretching and Controlled Anodization. Adv. Mater. Interfaces 2025, 12, 2400699. [Google Scholar] [CrossRef]
  20. Remešová, M.; Tkachenko, S.; Kvarda, D.; Ročňáková, I.; Gollas, B.; Menelaou, M.; Čelko, L.; Kaiser, J. Effects of Anodizing Conditions and the Addition of Al2O3/PTFE Particles on the Microstructure and the Mechanical Properties of Porous Anodic Coatings on the AA1050 Aluminium Alloy. Appl. Surf. Sci. 2020, 513, 145780. [Google Scholar] [CrossRef]
  21. Soffritti, C.; Fortini, A.; Nastruzzi, A.; Sola, R.; Merlin, M.; Garagnani, G.L. Dry Sliding Behavior of an Aluminum Alloy after Innovative Hard Anodizing Treatments. Materials 2021, 14, 3281. [Google Scholar] [CrossRef] [PubMed]
  22. Kim, H.S.; Kim, D.H.; Lee, W.; Cho, S.J.; Hahn, J.H.; Ahn, H.S. Tribological Properties of Nanoporous Anodic Aluminum Oxide Film. Surf. Coatings Technol. 2010, 205, 1431–1437. [Google Scholar] [CrossRef]
  23. Hu, N.; Ge, S.; Fang, L. Tribological Properties of Nano-Porous Anodic Aluminum Oxide Template. J. Cent. South Univ. Technol. 2011, 18, 1004–1008. [Google Scholar] [CrossRef]
  24. Lee, G.S.; Choi, J.H.; Choi, Y.C.; Bu, S.D.; Lee, Y.Z. Tribological Effects of Pores on an Anodized Al Alloy Surface as Lubricant Reservoir. Curr. Appl. Phys. 2011, 11, S182–S186. [Google Scholar] [CrossRef]
  25. Takaya, M.; Hashimoto, K.; Toda, Y.; Maejima, M. Novel Tribological Properties of Anodic Oxide Coating of Aluminum Impregnated with Iodine Compound. Surf. Coatings Technol. 2003, 169–170, 160–162. [Google Scholar] [CrossRef]
  26. Maejima, M.; Saruwatari, K.; Takaya, M. Friction Behaviour of Anodic Oxide Film on Aluminum Impregnated with Molybdenum Sulfide Compounds. Surf. Coatings Technol. 2000, 132, 105–110. [Google Scholar] [CrossRef]
  27. Tao, X.; Jianmin, C.; Jiazheng, Z.; Hongxin, D. The Pore-Enlargement and Self-Lubrication Treatment of Anodic Oxide Film of Aluminum. Wear 1996, 196, 214–218. [Google Scholar] [CrossRef]
  28. Wang, H.W.; Skeldon, P.; Thompson, G.E. Development and Tribological Assessment of Self-Lubricating Anodic Films on Aluminium. Surf. Coatings Technol. 1997, 88, 269–273. [Google Scholar] [CrossRef]
  29. Korzekwa, J.; Niedźwiedź, M.; Dercz, G.; Cwynar, K.; Sowa, M.; Bara, M.; Simka, W. Methods of Distributing the IF-WS2 Modifier for Its Introduction into the Structure of the Al2O3 Aluminum Oxide Coating. Coatings 2024, 14, 883. [Google Scholar] [CrossRef]
  30. Radek, N.; Pietraszek, J.; Gadek-Moszczak, A.; Orman, Ł.J.; Szczotok, A. The Morphology and Mechanical Properties of ESD Coatings before and after Laser Beam Machining. Materials 2020, 13, 2331. [Google Scholar] [CrossRef] [PubMed]
  31. Pietraszek, J.; Radek, N.; Goroshko, A.V.; Jana, A.; Ii, P. Challenges for the DOE Methodology Related to the Introduction of Industry 4.0. Prod. Eng. Arch. 2020, 26, 190–194. [Google Scholar] [CrossRef]
  32. Sieber, M.; Morgenstern, R.; Lampke, T. Anodic Oxidation of the AlCu4Mg1 Aluminium Alloy with Dynamic Current Control. Surf. Coatings Technol. 2016, 302, 515–522. [Google Scholar] [CrossRef]
  33. Kwolek, P.; Obłój, A.; Kościelniak, B.; Buszta, R.; Tokarski, T.; Krupa, K.; Gradzik, A.; Nowak, W.J.; Wojnicki, M.; Motyka, M. Wear Resistance of Hard Anodic Coatings Fabricated on 5005 and 6061 Aluminum Alloys. Arch. Civ. Mech. Eng. 2024, 24, 51. [Google Scholar] [CrossRef]
  34. ISO 21920-2:2021; Geometrical Product Specifications (GPS)—Surface Texture: Profile—Part 2: Terms, Definitions and Surface Texture Parameters. ISO: Geneva, Switzerland, 2021.
  35. Meng, F.; Zhou, Y.; Zhang, H.; Wang, Z.; Liu, D.; Cao, S.; Cui, X.; Nong, Z.; Man, T.; Liu, T. Development and Research Status of Wear-Resistant Coatings on Copper and Its Alloys: Review. Crystals 2025, 15, 204. [Google Scholar] [CrossRef]
  36. Krella, A. Resistance of PVD Coatings to Erosive and Wear Processes: A Review. Coatings 2020, 10, 921. [Google Scholar] [CrossRef]
  37. Zak, A.; Feldman, Y.; Lyakhovitskaya, V.; Leitus, G.; Popovitz-Biro, R.; Wachtel, E.; Cohen, H.; Reich, S.; Tenne, R. Alkali Metal Intercalated Fullerene-like MS2 (M = W, Mo) Nanoparticles and Their Properties. J. Am. Chem. Soc. 2002, 124, 4747–4758. [Google Scholar] [CrossRef] [PubMed]
  38. Rapoport, L.; Bilik, Y.; Feldman, Y.; Homyonfer, M.; Cohen, S.R.; Tenne, R. Hollow Nanoparticles of WS2 as Potential Solid-State Lubricants. Nature 1997, 387, 791–793. [Google Scholar] [CrossRef]
Materials 18 03471 g001
Figure 1. Thickness of coatings.
Figure 1. Thickness of coatings.
Materials 18 03471 g001
Materials 18 03471 g002
Figure 2. Microstructures of (a) the fresh cross-section (×10,000) and (b) the surface of the Al2O3/IF-WS2 coating.
Figure 2. Microstructures of (a) the fresh cross-section (×10,000) and (b) the surface of the Al2O3/IF-WS2 coating.
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Materials 18 03471 g003
Figure 3. (a) An example of a friction pair: oxide coating–cast iron pin; (b) photos of friction traces on unmodified Al2O3 oxide coatings (1–4) and modified Al2O3/IF-WS2 (5–8).
Figure 3. (a) An example of a friction pair: oxide coating–cast iron pin; (b) photos of friction traces on unmodified Al2O3 oxide coatings (1–4) and modified Al2O3/IF-WS2 (5–8).
Materials 18 03471 g003
Materials 18 03471 g004aMaterials 18 03471 g004b
Figure 4. (a) Picture of the cast iron pin; (b) SEM image of the etched surface; (c) EDS analysis of area 1 on the SEM image; (d) EDS analysis of point 2 on the SEM image; (e) EDS analysis of point 3 on the SEM image; (f) EDS analysis of point 4 on the SEM image; (g) EDS analysis of point 5 on the SEM image.
Figure 4. (a) Picture of the cast iron pin; (b) SEM image of the etched surface; (c) EDS analysis of area 1 on the SEM image; (d) EDS analysis of point 2 on the SEM image; (e) EDS analysis of point 3 on the SEM image; (f) EDS analysis of point 4 on the SEM image; (g) EDS analysis of point 5 on the SEM image.
Materials 18 03471 g004aMaterials 18 03471 g004b
Materials 18 03471 g005
Figure 5. (a) Wear track on sample 4, non-modified Al2O3; (b) SEM image of the wear track; (c) EDS analysis of area 1 on the SEM image.
Figure 5. (a) Wear track on sample 4, non-modified Al2O3; (b) SEM image of the wear track; (c) EDS analysis of area 1 on the SEM image.
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Materials 18 03471 g006
Figure 6. (a) Wear track on sample 5, modified Al2O3/IF-WS2; (b) SEM image of the wear track from the rectangular area in the “a” image; (c) EDS of area 1 on the “b” SEM image; (d) SEM image of the wear track from the circular area in the “a” image; (e) EDS of area 1 on the “d” SEM image.
Figure 6. (a) Wear track on sample 5, modified Al2O3/IF-WS2; (b) SEM image of the wear track from the rectangular area in the “a” image; (c) EDS of area 1 on the “b” SEM image; (d) SEM image of the wear track from the circular area in the “a” image; (e) EDS of area 1 on the “d” SEM image.
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Materials 18 03471 g007
Figure 7. (a) Pareto chart of the standardised effect for the Rq parameter; (b) plot of marginal means and 95% confidence limits for the Rq parameter.
Figure 7. (a) Pareto chart of the standardised effect for the Rq parameter; (b) plot of marginal means and 95% confidence limits for the Rq parameter.
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Materials 18 03471 g008
Figure 8. Means and standard deviation for the Rq parameter.
Figure 8. Means and standard deviation for the Rq parameter.
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Materials 18 03471 g009
Figure 9. (a) Pareto chart of the standardised effect for the Rk parameter; (b) plot of marginal means and 95% confidence limits for the Rk parameter.
Figure 9. (a) Pareto chart of the standardised effect for the Rk parameter; (b) plot of marginal means and 95% confidence limits for the Rk parameter.
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Materials 18 03471 g010
Figure 10. Means and standard deviation for the Rk parameter.
Figure 10. Means and standard deviation for the Rk parameter.
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Materials 18 03471 g011
Figure 11. (a) Pareto chart of the standardised effect for the Rvk parameter; (b) plot of marginal means and 95% confidence limits for the Rvk parameter.
Figure 11. (a) Pareto chart of the standardised effect for the Rvk parameter; (b) plot of marginal means and 95% confidence limits for the Rvk parameter.
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Materials 18 03471 g012
Figure 12. Means and standard deviation for the Rvk parameter.
Figure 12. Means and standard deviation for the Rvk parameter.
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Materials 18 03471 g013
Figure 13. Means and standard deviation for (a) the Rpk parameter and (b) the Rsk parameter.
Figure 13. Means and standard deviation for (a) the Rpk parameter and (b) the Rsk parameter.
Materials 18 03471 g013
Materials 18 03471 g014aMaterials 18 03471 g014b
Figure 14. 3D visualisation of (a) the surface of Al2O3 before tribological test; (b,d,f,h) the unmodified Al2O3 surface after the tribological test for samples 1, 2, 3, and 4, respectively; (c,e,g,i) the modified Al2O3/IF-WS2 surface after the tribological test for samples 5, 6, 7, and 8, respectively.
Figure 14. 3D visualisation of (a) the surface of Al2O3 before tribological test; (b,d,f,h) the unmodified Al2O3 surface after the tribological test for samples 1, 2, 3, and 4, respectively; (c,e,g,i) the modified Al2O3/IF-WS2 surface after the tribological test for samples 5, 6, 7, and 8, respectively.
Materials 18 03471 g014aMaterials 18 03471 g014b
Materials 18 03471 g015
Figure 15. (a) Pareto chart of the standardised effect for the intensity of the wear pin; (b) plot of marginal means and 95% confidence limits for the intensity of the wear pin.
Figure 15. (a) Pareto chart of the standardised effect for the intensity of the wear pin; (b) plot of marginal means and 95% confidence limits for the intensity of the wear pin.
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Materials 18 03471 g016
Figure 16. Friction coefficient vs. time for (a) the Al2O3 coatings and (b) the Al2O3/IF-WS2 coatings.
Figure 16. Friction coefficient vs. time for (a) the Al2O3 coatings and (b) the Al2O3/IF-WS2 coatings.
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Materials 18 03471 g017
Figure 17. (a) Pareto chart of the standardised effect for the friction coefficient μ; (b) plot of marginal means and 95% confidence limits for the friction coefficient μ.
Figure 17. (a) Pareto chart of the standardised effect for the friction coefficient μ; (b) plot of marginal means and 95% confidence limits for the friction coefficient μ.
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Table 1. Sonication parameters.
Table 1. Sonication parameters.
Dispersion LiquidTime [min]Power [kJ]Frequency [kHz]
Ethanol +15 g/L of IF-WS2 NPs51020
Table 2. Research test conditions.
Table 2. Research test conditions.
Sample
Designation		Test Input Variables
Introducing IF-WS2 NPsLoad [MPa]
1No (−1)0.3 (−1)
2No (−1)0.3 (−1)
3No (−1)0.6 (1)
4No (−1)0.6 (1)
5Yes (1)0.3 (−1)
6Yes (1)0.6 (1)
7Yes (1)0.3 (−1)
8Yes (1)0.6 (−1)
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Korzekwa, J.; Jarząbek, A.; Bara, M.; Niedźwiedź, M.; Cwynar, K.; Oleszak, D. Investigation of the Wear Resistance of Hard Anodic Al2O3/IF-WS2 Coatings Deposited on Aluminium Alloys. Materials 2025, 18, 3471. https://doi.org/10.3390/ma18153471

AMA Style

Korzekwa J, Jarząbek A, Bara M, Niedźwiedź M, Cwynar K, Oleszak D. Investigation of the Wear Resistance of Hard Anodic Al2O3/IF-WS2 Coatings Deposited on Aluminium Alloys. Materials. 2025; 18(15):3471. https://doi.org/10.3390/ma18153471

Chicago/Turabian Style

Korzekwa, Joanna, Adam Jarząbek, Marek Bara, Mateusz Niedźwiedź, Krzysztof Cwynar, and Dariusz Oleszak. 2025. "Investigation of the Wear Resistance of Hard Anodic Al2O3/IF-WS2 Coatings Deposited on Aluminium Alloys" Materials 18, no. 15: 3471. https://doi.org/10.3390/ma18153471

APA Style

Korzekwa, J., Jarząbek, A., Bara, M., Niedźwiedź, M., Cwynar, K., & Oleszak, D. (2025). Investigation of the Wear Resistance of Hard Anodic Al2O3/IF-WS2 Coatings Deposited on Aluminium Alloys. Materials, 18(15), 3471. https://doi.org/10.3390/ma18153471

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