Abrasive Wear Characteristics of High-Cr Multicomponent White Cast Irons at Elevated Temperatures

Abstract

The abrasive wear phenomenon at elevated temperatures is very common in industries where operations are performed under extreme conditions. The occurrence of abrasive wear at high temperatures is typically far more severe than that under room-temperature conditions. Industrial machine parts are much more prone to wear at extreme temperatures. Wear due to high-temperature abrasion leads to higher costs. Due to the risk of damaging machine parts and increased costs, it is significant to investigate materials that reverse this loss. It has been proven in previous studies that high-chromium white cast irons with multiple components, including vanadium, molybdenum, tungsten, and cobalt, called MWCIs, are among the most useful materials that can be selected as wear-resistant materials at high temperatures because of their dominant behavior against wear. In this study, three series of high-chromium multicomponent white cast irons (18Cr, 27Cr, and 35Cr MWCI) were used to test their abrasive wear resistance capability. A higher percentage of Cr leads to the precipitation of hard M7C3 carbides, which results in a higher carbide volume percentage (CVF) and hence higher hardness. However, the addition of excessive Cr and less C results in carbide refinement and a drop in hardness. The microstructure is primarily austenite. This study shows that, at an operating temperature of 1073 K, the 27CrMWCI performs the best as an abrasive wear-resistant material compared to 18CrMWCI and 35CrMWCI due to its (27CrMWCI’s) higher CVF and hardness.

1. Introduction

Wear is a significant occurrence that drastically damages machine parts. There are two types of wear that are common in industry, named erosive and abrasive wear. Abrasive wear occurs in materials between two contact surfaces with different hardnesses [1]. During the abrasive wear phenomenon, the surface is worn by particles of higher hardness than the surface’s hardness. In our previous study [2], it was found that the addition of Ti has limited contributions to tackling wear under room-temperature conditions. During high-temperature abrasive operations, the degree of abrasive wear is determined by factors such as the difference in hardness between the surfaces of the abrasive particles and the material surface, the applied load, and the creation of oxidation. Understanding the behavior of various materials in operation at elevated temperatures is crucial for designing suitable wear-resistant materials and advancing successful wear-reduction approaches. High-chromium white cast irons (HCCIs) are broadly utilized in circumstances where the wear phenomenon is common [3]. HCCIs are ferrous alloys that have a chromium content varying from 12 to 30 wt.% and a carbon content varying from 1.6 to 3.6 wt.% [4]. A notable number of authors have explored the influence of transitional materials to improve the wear resistance of cast irons. It has been clearly observed in earlier studies that transitional materials can significantly alter their stoichiometry and produce carbides that make a noteworthy contribution to HCCIs’ behavior against the wear phenomenon. The supplementation of transitional alloys aims to reshape eutectic carbides to increase hardness, improve the hardenability of the matrix, and restrain pearlite formation in areas with these alloying elements between the eutectic carbides and the matrix [5,6]. C absorption in the matrix is immensely important for the carbide volume fraction (CVF). Furthermore, the carbide volume fraction (CVF), which increases with increased C percentage, leads to increased hardness and wear resistance [7]. In as-cast situations, these alloys of HCCI mainly contain a metastable austenitic matrix with M7C3 carbides [8], and this can be converted into martensite by heat treatment [9]. These alloys’ high hardness and resistance to wear might be achieved with plenty of eutectic carbides, where the addition of the transition metals Mo, V, and W makes a noteworthy contribution. The effect of the added Mo, V, and W to high-chromium white cast iron is an improvement in hardenability, carbide precipitation, and, finally, hardness. However, high hardness does not always ensure higher abrasive wear resistance. Especially under high-temperature conditions, the abrasive wear resistance of very hard carbides starts to decrease quickly. A greater amount of C and Cr leads to densely precipitated eutectic carbides, resulting in greater hardness and wear resistance; however, it negatively affects toughness [10]. HCCIs solidify as primary austenite dendrites with a network of interdimeric eutectic carbides. Primarily, during the destabilization heat treatment stage, the austenite is converted into martensite [4,11,12,13]; however, for this study on high-temperature abrasive wear, the specimens were not heat-treated as the experimental conditions were extreme. Austenitic irons usually show a hardness in the range of 500–520 HV, and there are specific applications where this type of cast iron can be useful. The supplementation of Ti, Nb, and V can notably assist in the formation of MC primary carbides, which a considerable number of scholars have observed. Bedolla et al. [8,9,14] observed that if Nb and Ti are added to HCCI, NbC and TiC carbides will be formed. Xiaojun et al. noted that TiC can influence the production of primary M₇C₃ carbides, which demonstrates that the final particle size is significantly refined without clustering in the matrix [15]. Wear resistance is also substantially affected by the matrix’s toughness [16]. The addition of W to HCCI assists in increasing the matrix hardness, which decreases the wear rate, according to Anijdan et al. [17]. Molybdenum addition enhances HCCI’s wear resistance, according to Shimizu et al. [18]; Bouhamla et al. [19] reported a similar result. In addition, it has been found in previous research [2] that larger carbides are helpful for tackling wear resistance under room-temperature conditions; however, performance under high-temperature conditions requires further observation.

Studies on the abrasive wear of high-chromium cast irons have been ongoing for a long time; this study contributes new advancements in several key ways. Firstly, this study investigates multicomponent white cast irons (MWCIs) containing vanadium, molybdenum, tungsten, and cobalt in combination with different percentages of chromium (18Cr, 27Cr, 35Cr). This composition has previously been narrowly investigated in the literature, especially for its high-temperature (1073 K) wear resistance. Secondly, this research methodically compares chromium content, carbide volume fraction (CVF), hardness, and microstructural characteristics to abrasive wear resistance, determining the ideal chromium content for attaining the best performance at elevated temperatures and providing significant insight into material design. Thirdly, by focusing on wear behavior at 1073 K, this study addresses an industrially critical temperature range often overlooked in prior research, which predominantly targets room temperature or moderately elevated temperatures.

2. Experimental Procedures

2.1. Material Preparation

For this research, high-chromium white cast iron (HCCI) with 18 wt.%, 27 wt.%, and 35 wt.% Cr (Hokkaido Special Cast Steel, Hokkaido, Japan) was used as the base metal, where 18 wt.% and 27 wt.% Cr HCCI contains 3 wt.% C, and 35 wt.%Cr HCCI contains 2 wt.% C. The alloying elements Mo, W, V, and Co at a concentration of 3 wt.% were incorporated into these base metals to obtain the multicomponent white cast iron (MWCI). There were three test specimens in total. The manufacturing process for the specimens can be described briefly. A high-frequency induction furnace was employed to melt 100 kg of raw material. The melted material was poured into a chemically bonded silica sand mold with dimensions of 1140 mm × 900 mm × 200 mm to produce 12 pieces of plate-like ingots, each with dimensions of 290 mm × 80 mm × 20 mm, and later, the ingots were cut into dimensions of 50 mm × 50 mm × 10 mm using a high-speed precision cutting machine (Refinetech Co., Ltd., RCA-234, Kanagawa, Japan). The accurate weight percent of each alloy was calculated using SPECTROLAB (AMETEK, Inc., Berwyn, PA, USA), and the findings are shown in

Table 1. Chemical composition of the specimens (wt.%).

Test Material	C	Cr	Mo	W	V	Co	Mn	Si	S	Fe
18Cr MWCI	2.91	17.01	2.84	2.61	2.85	2.71	0.24	1.39	0.03	Bal.
27Cr MWCI	2.93	26.59	2.64	2.78	2.93	2.62	0.20	1.10	0.05	Bal.
35Cr MWCI	1.93	34.39	2.79	2.81	2.89	2.66	0.17	0.82	0.01	Bal.

. Scanning electron microscopy (JEOL Ltd., Akishima, Tokyo, Japan) merged with energy-dispersive X-ray spectroscopy (SEM+EDS) was employed to inspect the microstructure before and after etching in 5% nitrohydrochloric acid. The carbide type was determined through the technique of point analysis applied to SEM-EDS mappings. The carbide volume fraction (CVF) was calculated using ImageJ (ImageJ1.53t, National Institutes of Health, MD, USA) software [20]. The carbide size measurement was performed using ImageJ software. Firstly, an SEM image was taken using this software, and the scale was set as the SEM image scale. Later, a line was drawn on individual grains (carbides). This was repeated on every carbide in the image, and results were achieved. X-ray diffraction (Ultima IV, Rigaku, Tokyo, Japan, with a Cu-K∝ source) was employed to investigate the microstructural phase of the material. A 3D laser microscope (Lasertec Hybrid, Yokohama, Japan) was employed to observe the wear depth of the worn surface.

2.2. High-Temperature Abrasive Wear Testing

The investigation of the high-temperature abrasive wear characteristics of the 50 mm × 50 mm × 10 mm specimen took place utilizing a high-temperature abrasion tester designed by our research team, as shown in Figure 1. The test specimen was put in the holder of the machine and heated to the target temperature by a heater, and then a cubic boron nitride (CBN) wheel was pressed onto the specimen’s surface with a load of 61.73 N. The granularity of the CBN was 140, with an average grain size of 105–120 µm, and the wheel was dressed after each test. The test temperature was set at 1073 K, the rotation speed at 350 rpm, and the test time at 30 s. As an evaluation method, we used a formula for finding out the wear rate, shown here in Equation (1). An electronic weighing machine was utilized to weigh the specimens both before and after the test, and then the volumetric loss was measured.

$$\mathrm{Wear}\mathrm{Rate}[{\mathrm{m}\mathrm{m}}^3/\mathrm{N}.\mathrm{m}]={\displaystyle \frac{\left(\mathrm{W}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{R}\mathrm{e}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\right[\mathrm{g}]/\mathrm{D}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}[\mathrm{g}/{\mathrm{m}\mathrm{m}}^3\left]\right)}{\mathrm{L}\mathrm{o}\mathrm{a}\mathrm{d}\left[\mathrm{N}\right]/\mathrm{M}\mathrm{i}\mathrm{l}\mathrm{e}\mathrm{a}\mathrm{g}\mathrm{e}\left[\mathrm{M}\right]}}$$

(1)

2.3. High-Temperature Vickers Hardness Test

An AVK-HF Vickers-type hot hardness tester from Mitutoyo Co., Kanagawa, Japan, was used as the Vickers hardness machine during the high-temperature hardness test in this study. To prepare the specimens for the Vickers hardness test, specimens measuring 7.0 mm × 7.0 mm × 5.0 mm were cut and polished. Hardness measurements for every specimen were performed 5 times at 1073 K in an argon atmosphere. A diamond indenter was utilized with a load of 9.9 N applied for 10 s.

3. Results and Discussion

3.1. Metallographic Observation

The metallographic observation took place using a scanning electron microscope (SEM) for every specimen. To perform the metallographic observation, all the specimens were separately etched in 5% nitrohydrochloric acid for several minutes. The results from the metallographic observation of the specimens are shown in Figure 2. The SEM microphotographs highlight a considerable presence of eutectic carbides dispersed all over the microstructure. Amongst these, M₇C₃ carbide is recognized as the main and most dense carbide, while the matrix in which these carbides are implanted is largely composed of austenite. There are several reasons behind this austenite matrix, such as the fact that the specimens were as-cast, the casting method was rapid cooling, the carbon percent was higher, and there was a micro-segregation effect during solidification. It was detected that the volume fraction of carbides increased gradually with increasing chromium (Cr) content in the white cast iron (WCI) alloys. Precisely, the carbide volume fraction was measured to be 26.69%, 37.36%, and 31.1% for the 18CrMWCI, 27CrMWCI, and 35CrMWCI alloys, respectively. The carbide volume fraction (CVF) of the three series of specimens is displayed in Figure 3. This phenomenon of a surge in the carbide percentage is attributed to segregation during the alloy’s solidification procedure, where Cr-enriched areas encouraged the development of carbides. The metallographic investigation provided additional evidence that Cr has a considerable impact on carbide formation. The existence of Cr encourages the development of M₇C₃ carbides, which tend to dominate in the microstructure as the Cr content increases.

Usually, M₇C₃ carbides consist of a hexagonal Bravais lattice structure; this is usual for these kinds of carbides; however, an orthogonal crystal structure may have been detected a few times in odd scenarios. Increasing the chromium content not only enhances the overall number of M₇C₃ carbides but also acts as an important player in refining these carbides, leading to a more uniform distribution and refined microstructure. This occurrence of carbide refinement (a decrease in the carbides’ average size) is especially observed in the specimens with a higher Cr content, namely the 27CrMWCI and 35CrMWCI alloys. In these specimens, the higher percentage of chromium content results in more densely distributed carbides. This characteristic of carbide refinement improves the alloy’s general wear resistance, leading to its greater mechanical properties.

In this study, with the addition of Mo, W, and V, a fraction of M₂C and M₃C carbides were found instead of MC carbides, and there are several reasons for this, such as interactions between the alloying elements, thermodynamic stability, the solidification sequence, and the carbon percentage. Mo, W, and V interact with C and Cr, which results in complex carbide formation. These alloying elements tend to participate in the formation of M₂C carbides, which are high in Mo and W, while at the same time dissolving Cr [21]. M₂C carbides have the characteristic of being more thermodynamically stable over a specific composition range and under certain cooling conditions in comparison to MC carbides [4,22]. The formation of M₂C carbides is aided by Mo and W in high-chromium white cast irons [23]. In addition, higher percentages of carbon content play a crucial role in forming M₂C and M₃C carbides over MC carbides in high-chromium white cast irons [4].

Remarkably, with the increased chromium percentage added to the material, the production of M₂C carbides declined. This decline in M₂C carbide content in the microstructure is a significant factor that indicates that a higher percentage of Cr content leads to the consumption of much of the carbon content present in the microstructure. This consumption of carbon with greater Cr percentages leads to a lack of M₂C carbide precipitation. At the same time, chromium-enriched M₇C₃ carbides undergo much denser precipitation; this precipitation behavior hinders M₂C precipitation and further increases the number of M₂C carbides. This characteristic illustrates the significant role that chromium plays in regulating carbide precipitation, impacting both the types and distributions of carbides in the alloy. This improvement in Cr content is very likely to improve the wear resistance behavior and overall robustness of high-chromium white cast irons while favoring the formation of hard M₇C₃ carbides and causing a reduction in softer M₂C carbides.

The M₇C₃ carbides in the microstructure of the 18CrMWCI and 27CrMWCI specimens appear to be mainly hexagonal and rod-like; however, in 35CrMWCI, a hexagonal, plate-like shape is observed. In addition, the M₂C carbides appear fishbone-like in all the specimens that are shown in

Table 2. Characteristics of precipitated carbides analyzed by point analysis method.

Alloy	Carbide Type	Carbide Compound	Shape	Carbide Structure
18CrMWCI	MC	-	-	-
	M2C	(Fe59.77Mo2.17W0.49)C5.41	Fishbone-like	Hexagonal
	M7C3	(Fe59.89Cr25.19V1.86)C5.27	Hexagonal rod-like plate	Hexagonal
27CrMWCI	MC	-	-	-
	M2C	(Fe51.28Mo2.38W0.47)C5.95	Fishbone-like	Hexagonal
	M7C3	(Fe51.60Cr33.67V1.17)C5.30	Hexagonal rod-like plate	Hexagonal
35CrMWCI	MC	-	-	-
	M2C	(Fe47.33Mo1.82W0.38)C4.16	Fishbone-like	Hexagonal
	M7C3	(Fe47.48Cr40.10V1.19)C3.91	Hexagonal plate-like	Hexagonal

. This identification of carbides was performed with the point analysis method. Point analysis concentrates on particular characteristics; it involves high-resolution imaging and an elemental investigation to examine material properties, whereas mapping demonstrates the spatial distribution of elements across a larger area. Usually, an SEM image is used to select points or areas of importance, such as grains, inclusions, or defects. Point analysis presents accurate elemental data in these areas, creating a thorough spectrum for every point. EDS mapping enhances this by visualizing elemental gradients and phase distributions throughout the area. Table 2 shows the results of the point analysis, where the types of carbides, carbide compounds, shape, and structure are given. However, it is difficult to discern the carbide type from this point of view. As a result, X-ray diffraction calculations are displayed in Figure 4. The carbide peaks are higher in the samples with a higher Cr content (27Cr MWCI and 35CrMWCI) compared to the sample with a lower Cr content (18CrMWCI). The carbides are mainly M₇C₃ carbides, and there is a small presence of M₂C and M₃C, which shows that Mo and W exist in M₂C carbides, although Cr and V are dominant in M₇C₃. Research findings by A. B. Jacuinde [14], where it is confirmed that vanadium carbide (VC) does not demonstrate precipitation behavior during the solidification process by considering the 17Cr and 2V content of white cast iron materials, are in agreement with the insufficient crystallization of V observed as MC carbides are formed in the present research findings.

The distribution and location of every transition metal in the microstructure of the specimens were investigated utilizing energy-dispersive X-ray spectroscopy (EDS) analysis, and the findings are shown in Figure 5. The authors used point analysis in the SEM and EDS analyses for the 18Cr, 27Cr, and 35CrMWCI specimens to display the chemical composition of carbides. Ten different zones were selected to repeat the experiment, and the results were collected. Not only were Cr, Fe, and C components present in the M₇C₃ carbides, but V was also detected. Fe, Mo, and W comprised much of the M₂C carbides. In contrast, cobalt and iron were equally incorporated into the matrix. Conversely, it could be assumed that cobalt did not function as a carbide-forming agent in the current study. It could be debated that the capability of every supplemented transition metal to produce eutectic carbides and secondary carbides is significantly affected by the complete composition of the materials. A high-temperature abrasive wear test was conducted to determine all these effects on the wear characteristics of the materials; the results will be discussed in the upcoming section.

3.2. High-Temperature Vickers Hardness

The hardness of every material at the time of operation in an environment of elevated heat plays a significant role in determining its capability to resist the wear phenomenon at the actual time of operation. It is notably important to understand these characteristics because materials are often exposed to high temperatures and mechanical pressures in various real operational applications. Figure 6 shows the Vickers’ hardness results at high temperatures. The data indicate that as the Cr content in the specimens increased, there was a subsequent increase in hardness. This property of the materials’ improved hardness highlights that it is important to add more chromium to high-chromium white cast irons to improve the material’s resistance to wear at elevated temperatures. However, the excessive addition of Cr may require further investigation regarding changes in chemical composition. Among all three specimens (18CrMWCI, 27CrMWCI, 35CrMWCI), 27Cr MWCI showed the highest hardness value at 310.63 HV, which is a 66.66% increase. However, with the increase in chromium for the 35CrMWCI specimen, there was a decrease in hardness to 232.90 HV, which is a 25% decrease. The reason behind this decline in hardness for the specimen with the highest Cr content (35CrMWCI) is presumed mainly to be the reduced carbide volume fraction; the carbon content is lower in the 35CrMWCI specimen (1.93 wt.%) compared to the 27CrMWCI specimen (2.93 wt.%). Carbon is necessary for forming carbides, especially for chromium carbides. The lowered percentage of carbon in the 35CrMWCI specimen restricts the formation of carbides, although there is a higher percentage of chromium. In addition, with a higher percentage of chromium (35 wt.%), the alloying composition may alter its equilibrium to stabilize primary austenite at the time of solidification. A greater primary austenite fraction implies limited carbides in the as-cast composition. A CVF graph is illustrated in Figure 3 in the previous section.

3.3. High-Temperature Abrasive Wear Performance

In this study, at 1073 K, a high-temperature abrasive wear test was conducted. Figure 7a shows that the maximum abrasive wear rate was observed in the 18CrMWCI specimen (6.52 × 10⁻² mm³/N.m). However, with the increase in Cr content, the abrasive wear started to decline. The abrasive wear rate in the 27CrMWCI specimen was found to be 3.456 × 10⁻² mm³/N.m. However, due to its lower hardness and carbide volume fraction (CVF), the 35CrMWCI specimen showed an increase in the abrasive wear rate to 3.9420 × 10⁻² mm³/N.m. The abrasive wear rate in the 27CrMWCI specimen was around 47% less in comparison with the abrasive wear rate in the 18CrMWCI specimen and 14% lower than in the 35CrMWCI specimen. Presumably, the higher carbide volume fraction, uniformly formed carbide shapes, and greater hardness are the reasons for the superior wear resistance of the 27CrMWCI specimen. A very evident relationship can be observed between the carbide volume fraction (CVF) and the abrasion wear rate in Figure 7b. After observing Figure 5, Figure 6, Figure 7 and Figure 8, it can be said that in the case of the 18CrMWCI specimen, containing a lower carbide volume fraction (CVF 26.69%), a higher wear rate is observed in comparison with the 27CrMWCI specimen, which contains a higher carbide volume fraction (CVF 37.36%). However, the 35CrMWCI specimen indicates a rise in the rate of wear with a CVF of 31.1%. Another relationship can be drawn from Figure 7c, where the hardness significantly influences the wear rate. It is shown that the specimen with the highest hardness, 27CrMWCI, exhibits the lowest wear rate. So, it can be said that hardness is one of the most significant determiners of the abrasive wear rate.

3.4. Worn Surface Analysis

Figure 8 presents the morphologies of the abrasively worn surfaces of specimens subjected to high-temperature abrasive wear experiments under an applied load of 61.73 N at a temperature of 1073 K. To obtain a thorough understanding of the chemical behavior at the time of the abrasive wear process, an EDS (energy-dispersive spectroscopy) investigation was also performed, and the EDS photographs collected are displayed in Figure 9. Among the experimental specimens, the 27Cr MWCI specimen exhibited exceptional abrasion resistance in comparison to the others. A definite assessment with the help of high-magnification SEM (scanning electron microscopy) showed evidence of microcutting predominantly inside the material’s matrix. This microcutting seems to be present because of the lower microhardness of the matrix, implying that elevating the hardness of the material has a probable contribution to mitigating such wear mechanisms.

Moreover, micro-ploughing is observed on every specimen’s worn surface, particularly clustered in the carbide areas. These ploughing phenomena might be the result of the brittleness of carbides, and these characteristics make them likely to chip and peel off during the high-temperature wear process. It is worth mentioning that during the abrasive wear test of 18Cr MWCI, almost all the M₇C₃ carbides were likely to peel off, although equally, on the surface of the 27Cr MWCI and 35Cr MWCI specimens, the carbides continued to stay on and contribute to keeping the matrix robust. However, fully understanding the distinctive characteristics of M₇C₃ carbides during the abrasive wear phenomenon for the various specimens remains difficult. Consequently, extra cross-sectional inspections were performed on every specimen’s abrasively worn surface to investigate these variations in further detail. These studies aimed to offer a deeper understanding of the wear mechanisms of all three specimens. Figure 10 shows the wear depth of all three specimens. It was found that the highest wear depth was observed in the 18CrMWCI specimen at 443.32 µm; however, for 27CrMWCI, the wear depth was 322.02 µm, and for 35CrMWCI, it was 348.774 µm. This shows that the wear resistance behavior of the 27CrMWCI specimen is profound, which is caused by its hardness and CVF.

3.5. Worn Surface Analysis Through Cross-Section

Figure 11a displays the cross-sectional SEM microphotographs of the three specimens: 18CrMWCI, 27CrMWCI, and 35CrMWCI. To understand the chemical distribution of the elements, the EDS data are also provided in Figure 11b. The 18CrMWCI specimen exhibits severe wear in the matrix, whereas mild wear is observed in the matrix for the 27Cr MWCI and 35CrMWCI specimens, which is in agreement with the worn surface morphologies observed. However, a severely broken phenomenon is observed for the more Cr-enriched specimens, 27CrMWCI and 35CrMWCI. The matrix of the 18CrMWCI specimen seems to be inferior to those of the 27CrMWCI and 35CrMWCI specimens, which could be credited to the decrease in hardness and their less dense carbides. It can be presumed that during the abrasive wear phenomenon, the abrasive wheel particles hit the matrix of the 18CrMWCI specimen because of its lack of carbides; on the other hand, for 27CrMWCI and 35CrMWCI, the carbides face abrasive hits from the stone wheel particles. As the hardness of the matrix is lower than that of the carbides (M₇C₃), the matrix peels off, along with the carbides. However, the matrix conditions of the 27Cr MWCI and 35CrMWCI specimens are better than those of the 18Cr MWCI specimen because of their denser carbides (M₇C₃). The matrix-stabilizing behavior of M₇C₃ gives the matrix extra strength. During the abrasive wear process, the stone wheel particles hit the dense carbides first, and the carbides brake, but the matrix remains comparatively intact. It can, as a result, be summarized that, in the case of the 18CrMWCI specimen, the abrasive particles from the stone wheel would primarily scrape the matrix, resulting in fracturing, peeling, and the formation of microcutting canals, and afterwards, they would strike the carbide particles with rigorous force, resulting in the creation of pits on the worn surface. Since they are fragile, coarser carbides peel off immediately when the abrasive particles meet the M₇C₃ carbides. Accordingly, peeling and microcutting were found to be the primary abrasive wear mechanisms in the current study, and micro-pitting can be considered a sub-mechanism.

4. Conclusions

In this study, a high-temperature abrasive wear experiment was performed using three high-chromium-based multicomponent white cast iron specimens (18CrMWCI, 27CrMWCI, 35CrMWCI). The conclusions of this study can be summarized as follows:

• Adding Cr leads to the precipitation of various carbides, especially M₇C₃ carbides, which precipitate densely. This increase in Cr content leads to a higher CVF, where 27CrMWCI showed the highest CVF; however, the specimen with the highest percentage of Cr showed a decline in the CVF (35CrMWCI).
• The hardness of the specimens is significantly influenced by the CVF. The 27CrMWCI specimen showed the highest hardness, while the 18CMWCI specimen showed the lowest. This decline in hardness was the result of a lack of carbides, and lower hardness contributes to a higher wear rate, which is in agreement with several previous studies.
• The abrasive wear mechanism at high temperatures can be briefly explained as follows: In the 27CrMWCI specimen, the higher percentage of carbides provided better safety against wear by guarding the softer matrix from abrasive particles. In the 18CrMWCI and 35CrMWCI specimens, less carbides left the matrix uncovered, leading to a higher wear rate.