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Article

Mechanical and Tribological Behaviors of Hot-Pressed SiC/SiCw-Y2O3 Ceramics with Different Y2O3 Contents

by
Shaohua Zhang
1,2,3,
Jinfang Wang
2,3,
Meng Zhang
2,3,
Longqi Ding
2,3,
Huijun Chan
2,3,
Xiyu Liu
2,3,
Fengqing Wu
2,3,
Zhibiao Tu
2,3,
Ling Shao
2,3,
Nengyong Ye
2,3,
Sheng Dai
2,3,
Liu Zhu
2,3,* and
Shichang Chen
1,*
1
School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou 310018, China
2
School of Materials Science and Engineering, Taizhou University, Taizhou 318000, China
3
Zhejiang Provincial Key Laboratory for Cutting Tools, Taizhou University, Taizhou 318000, China
*
Authors to whom correspondence should be addressed.
Coatings 2023, 13(5), 956; https://doi.org/10.3390/coatings13050956
Submission received: 18 April 2023 / Revised: 8 May 2023 / Accepted: 15 May 2023 / Published: 19 May 2023
(This article belongs to the Special Issue Advances of Ceramic and Alloy Coatings)
Browse Figures
Versions Notes

Abstract

:
Sintering additives are commonly used to reduce the conditions required for densification in composite ceramics without compromising their performances simultaneously. Herein, SiC/SiCw-Y2O3 composite ceramics with 10 vol.% SiC whiskers (SiCw) and different Y2O3 contents (0, 2.5, 5, 7.5, and 10 vol.%) were fabricated by hot-pressed sintering at 1800 °C, and the effects of Y2O3 content on the microstructure, mechanical properties, and tribological behaviors were investigated. It was found that the increased Y2O3 content can promote the densification of SiC/SiCw-Y2O3 composite ceramics, as evidenced by compact microstructure and increased relative density. The Vickers hardness, fracture toughness, and flexural strength also increased when Y2O3 content increased from 2.5 vol.% to 7.5 vol.%. However, excessive Y2O3 (10 vol.%) aggregated around SiC and SiCw weakens its positive effect. Furthermore, the Y2O3 additive also reduces the coefficient of friction (COF) of SiC/SiCw-Y2O3 composite ceramics, the higher the Y2O3 content, the lower the COF. The wear resistance of SiC/SiCw-Y2O3 composite ceramics is strongly affected by their microstructure and mechanical properties, and as-sintered SiC ceramic with 7.5 vol.% Y2O3 (Y075) shows the optimal wear resistance. The relative density, Vickers hardness, fracture toughness, and flexural strength of Y075 are 97.0%, 21.6 GPa, 7.7 MPa · m1/2, and 573.2 MPa, respectively, the specific wear rate of Y075 is 11.8% of that for its competitor with 2.5 vol.% Y2O3.

1. Introduction

Owing to their excellent mechanical properties and abrasion resistance, silicon carbide (SiC) ceramics have been widely used in aerospace, petrochemical, and other fields [1,2]. However, the strong covalent bonding and low self-diffusion coefficient of SiC ceramics make it hard to sinter completely and get compacted microstructure [3]. Commonly, pure SiC ceramics require at least 2000 °C to get thoroughly compacted, and this considerable energy consumption should be taken seriously [1]. Besides, the high hardness of SiC also means its high brittleness, which may not be adaptable in some complex environments. Thus, it is necessary to improve the comprehensive performance of SiC ceramic against harsh work conditions.
Whisker strengthening is a very effective method to reduce the brittleness of hard ceramics. The commonly used reinforcements include SiC fibers [4], Si3N4 whiskers [5], SiC whiskers (SiCw) [6,7,8,9], and others. SiCw has better compatibility and has been widely used in the toughening study of SiC ceramics, owing to the same chemical composition and similar crystalline structure between SiC and SiCw. SiCw reinforcement has been used to enhance the mechanical properties, particularly the fracture toughness of SiC ceramics, due to its high elastic modulus and strength. The main toughening mechanisms include whisker bridging, pullout, crack deflection, and their combination [6,7,8,9]. Several articles [6,7] mentioned that with SiCw content increase, the mechanical properties of SiC ceramics increase first and then decrease. Yang et al. [8] reported that the proper content of SiCw reinforcements could enhance the wear resistance, which was ascribed to the improved mechanical properties of SiC ceramics. However, few studies on SiCw-reinforced SiC ceramics fabricated by hot-pressed sintering have been reported.
Recently, several articles have shown that SiC powders can be densified by incorporating sintering additives at a lower sintering temperature without compromising their performance [10,11,12,13,14,15,16,17]. Therefore, various additives like Y2O3 [10], La2O3 [11], and RE(NO3)3 [12] (RE = rare earth element), etc., as well as the combination of Al2O3-RE2O3 [13,14,15], AlN-RE2O3 [16,17], and Er2O3-Y2O3 [18] have been used in the sintering of SiC ceramics to improve its sinterability by liquid phase generation. Further, the Y2O3 additive has been used in various ceramics, including SiC [19,20,21,22], Si3N4 [23,24], TiC [25], ZrB2-SiC [26,27,28,29,30], AlN-SiC [31], WC [32,33,34], and cordierite [35], etc. Some references [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35] mentioned that the Y2O3 additive could promote the densification of the materials and influence their mechanical properties. Cheng et al. [25] presented that Y2O3 can improve the mechanical properties of TiC ceramics by pinning at the grain boundary. Zhang et al. [26] discovered that appropriate Y2O3 addition could eliminate surface oxides and suppress grain growth to promote the densification of ZrB2-SiC ceramics. Several articles [10,19,20,21,22] reported that the Y2O3 additive could improve the densification of SiC ceramics at a higher sintering temperature (1900–2000 °C) to achieve excellent performance. It demonstrates that Y2O3 additions can accelerate the diffusion and mass transfer between the SiC matrix during sintering [12,20]. However, a much higher temperature can deteriorate the mechanical properties by vaporizing the liquid phase and generating pores [36]. Gupta et al. [37] reported that a small amount of Y2O3 addition could improve the mechanical and tribological properties of β-SiC ceramics. However, the preparation of SiC/SiCw-Y2O3 composite ceramics and the effect of Y2O3 content on the mechanical and tribological properties have rarely been reported.
To obtain compact SiC ceramics at a comparatively lower sintering temperature and improve their mechanical and tribological properties simultaneously, Y2O3 and SiCw are incorporated to fabricate the SiC/SiCw-Y2O3 composite ceramics by hot-pressed sintering (HP) at 1800 °C. SiCw is used as the reinforcement and kept at 10 vol.%. Y2O3 is the sintering additive, with content increasing from 0 to 10 vol.%. The effects of Y2O3 contents on the microstructure, mechanical properties, and tribological behaviors of the SiC/SiCw-Y2O3 composite ceramics were investigated. This study can provide constructive suggestions and references to the field of SiC ceramic modification.

2. Experimental

2.1. Raw Powders

Alpha-SiC nanoparticles (≥99.9%, ~100 nm, Forsman, Beijing, China), β-SiCw (≥99.9%, D0.5 μm-L12 μm, Forsman, Beijing, China), and Y2O3 nanoparticles (≥99.9%, ~50 nm, Aladdin, Shanghai, China) were used in this study to sinter the SiC/SiCw-Y2O3 ceramics. FE-SEM (scanning electron microscopy, S-4800, HITACHI, Tokyo, Japan) images of the 3 raw powders and their XRD (X-ray diffractometer, D8 Advance, Bruker, Billerica, MA, USA) patterns are shown in Figure 1. SiC powders are irregular polygonal particles with a main crystalline structure of 6H-SiC (PDF-# 72-0018). SiCw has a diameter of ~0.5 μm and a main crystalline structure of 3C-SiC (PDF-# 75-0254). Y2O3 (PDF-# 65-3178) is a subspindle floccule and agglomerated with adjacent ones. The obtained results confirmed the satisfactory morphology, size, and crystallinity of the raw powders.

2.2. Hot-Pressed Sintering of SiC/SiCw-Y2O3 Ceramics

To explore the effect of Y2O3 content on the microstructure and comprehensive properties of SiC/SiCw-Y2O3 ceramics, Y2O3 with volume content of 0%, 2.5%, 5%, 7.5%, and 10% (denoted as Y000, Y025, Y050, Y075, and Y100, respectively) were investigated in this study. SiCw contents were kept constant (10 vol.%), and SiC contents were in balance. The purchased powders were mixed according to their designed formula, then with ZrO2 balls of 10 times the weight of the obtained powder and ethanol in the polyamides jar. The ball-milling of the raw powders was conducted by a planet-ball-grinding machine (MIRT-QMQX-4L, Miqi, Changsha, China), and the mill lasted without intervals for 12 h with a speed of 180 r/min. The ball-milled powders were dried, sieved, and pre-compacted in a graphite mold coated with graphite paper. Then, the green compacts were fabricated by a vacuum hot-pressed sintering furnace (ZT-40-21Y, Chenhua, Shanghai, China) to obtain SiC/SiCw-Y2O3 composite ceramics with dimensions of φ26.5 mm × 6.5 mm. The sintering process was conducted at 1800 °C for 1 h under the pressure of 40 MPa in a vacuum atmosphere. The detailed sintering procedure can be found in Figure 2.

2.3. Sample Characterization

The as-sintered ceramics were polished by the diamond polishing disc and silk flannelette. The diamond spray with sizes gradually decreased to 0.25 μm was used during polishing. The specimen surfaces were finally polished to average roughness below 0.4 μm. The phase compositions of the as-sintered ceramics were detected by the mentioned XRD. Before XRD detection, the composite ceramics were carefully polished. The fracture morphologies of the composite ceramics were obtained by the three-point bending method and observed by the SEM (S-4800, HITACHI). The morphologies and chemical composition of the polished ceramics were examined by a photo-diode back-scattered electron (PDBSE) detector and an energy-dispersive X-ray spectrum (EDS, X-MaxN 20, Oxford, Oxford, UK) detector equipped on the SEM.

2.4. Mechanical Properties

The evaluations of the mechanical properties for each group were repeated at least 5 times, and the obtained results are presented as means ± standard deviations.

2.4.1. Relative Density

Since the compactness of the as-sintered ceramics is closely related to their mechanical properties, thus, the relative density test and the corresponding results and discussion are included in the mechanical properties evaluation section. The bulk density was measured by an analytical balance (ME204, Mettler, Zurich, Switzerland) separately in air and deionized water at least 5 times, and the value of relative density (%) was calculated by the Archimedes method [11].

2.4.2. Vickers Hardness

The Vickers hardness (HV, GPa) of SiC composite ceramics with different content of Y2O3 was tested by a Vickers hardness tester (HV-50Z, Huayin, Laizhou, China) with a load of 20 kgf for 15 s. The length of the diagonal indentation (2a) and the final Vickers hardness value were obtained by the standard GB/T 4340.1-2009.

2.4.3. Fracture Toughness

The indentation fracture toughness (KIC, MPa · m1/2) of each group was obtained by the Vickers hardness tests mentioned above. The parameters, including the length of the diagonal hardness indentation (2a) and the crack along the edge of the indentation (2c), were precisely measured by the metallomicroscope (Axio Imager A2m, Zeiss, Oberkochen, Germany). Young’s modulus (E) of the SiC matrix as 400 GPa was reported by Guo et al. [38]. The value of indentation fracture toughness was calculated by Equation (1) according to the Niihara [9,38,39].
K I C = 0.0181 E 0.4 H V 0.6 a ( c − a ) − 0.5

2.4.4. Flexural Strength

The flexural strength (σ, MPa) was investigated by a universal testing machine (CMT5305, MTS, Eden Prairie, MN, USA) with a cross-head speed of 0.2 mm/min and a span of 14.5 mm. The maximum applied load of the flexural fracture was recorded and calculated according to the 3-point bending method to obtain the value of flexural strength. Besides, the bar-shaped samples for the flexural strength test should conform to the requirement given by the standard GB/T 3851-2015 (a size of 5.5 mm × 6.25 mm × 20 mm).

2.5. Tribological Behavior

A tribometer (MFT-5000, RTEC) was used to investigate the tribological behavior of the SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents. The specimens were polished to surface roughness below 0.4 μm before the tribological test, aiming to reduce the imperfections like scratches that would interfere with the results. The linear-reciprocating wear tests were conducted at room temperature and dry conditions with a frequency of 2 Hz, P is the applied load (20 N), sliding time of 20 min, a stroke length of 5 mm, and s is the friction stroke length (12 m). YG6 balls (6 wt.% Co, Vickers hardness: 20 GPa) with a diameter of 6.35 mm were used as friction pairs in the tests. The tribological test for each group was carried out 3 times, and the representative results were exhibited in Section 3. The coefficient of friction (COF) variation with sliding time was recorded automatically by the tribometer. The partial roughness of the worn surface can be represented by the 2D profiles and 3D morphologies characterization of the wear tracks instead of measuring the entire surface roughness after the wear test. The 2D and 3D profiles of the wear tracks were reconstructed by the equipped white-light interferometric profilometer. SEM images of the wear scar were obtained to analyze the wear morphology and type. The geometric parameters of wear scars (mm) and wear volume (V, mm3) were obtained by white light interferometer data, and the specific wear rate (WR, mm3/(N · m)) was calculated according to Equation (2) that researchers mentioned [8,40].
W R = V P s

3. Results and Discussion

Figure 3 shows the fracture morphologies of SiC/SiCw-Y2O3 composite ceramics obtained by the three-point bending tests. The porous microstructure can be observed in the Y000 and Y025 groups (Figure 3a,b), indicating their low compactness. As Y2O3 content increases, the number of pores on the fracture morphologies of the Y050, Y075, and Y100 groups is significantly reduced, and the connection between the grains becomes tight (Figure 3c–e). Thus, it can be concluded that the increased Y2O3 content can facilitate the compacting of SiC/SiCw-Y2O3 composite ceramics. Besides, the embedded SiCw and their pullout locations (yellow arrow) in the composite ceramics have also been pointed out. The SiCw with high elastic modulus and low crystal defects can withstand the external force and not easy to generate the whisker fracture. The matrix fracture occurs when a high external force is applied and beyond the load-bearing capacity of the SiC matrix and SiCw. During fracturing, when the external force exceeds the interface bonding force between SiCw and SiC matrix, the SiCw pullout phenomenon occurs [8,9].
To further reveal the microstructure characteristic of the compacted ceramic, the morphologies of Y075 and Y100 groups after careful polishing were observed by SEM (PDBSE mode), as shown in Figure 4a,b. The quantitative EDS was performed to estimate the Y2O3 content of the detected points with different grayscale areas, as shown in Figure 4b,c (for Y075) and Figure 4e,f (for Y100). It can be found that Y2O3 (area with lighter grayscale) filled in the gaps between SiC and SiCw, proving that liquefied Y2O3 can promote particle rearrangement and mass transfer to increase the density during sintering [12,25,27]. In the Y075 group, Y2O3 is evenly distributed and presents a slender outline between the SiC and SiCw. Sharma et al. [40] mentioned that the glassy phase distributed between the grain boundaries could enhance the fracture toughness by combining intergranular crack mode and energy-dissipating processes in the crack wake. In contrast, Y2O3 in the Y100 group shows severe aggregation. It can be predicted that excess Y2O3 aggregated around SiC and SiCw may deteriorate the mechanical and relevant properties of the composite ceramics [26,27].
XRD results are used to identify the phase composition of the SiC/SiCw-Y2O3 composite ceramics, as shown in Figure 5. Most of the characteristic peaks of SiC can be detected (regardless of their specific crystalline structure) in all groups. The results in Figure 1 and Figure 4 confirm the existence of SiC and SiCw in the composite ceramics. Except for Y000, the characteristic peaks (29.2° and 48.5°) belonging to PDF-#65-3178 can also be found in the rest groups, indicating the existence of Y2O3 in the composite ceramics. Moreover, the corresponding peak intensity of Y2O3 shows an increased trend with Y2O3 content increase. No new peaks and peaks shifting appear in the diffraction patterns, demonstrating the good stability of the three components during sintering.
The relative density, Vickers hardness, fracture toughness, and flexural strength of SiC/SiCw-Y2O3 composite ceramics are shown in Figure 6. Figure 6a shows that the relative density of composite ceramic increases with Y2O3 content; Y000 has the lowest value of 54.3%. With Y2O3 content increase to 2.5 vol.%, 5 vol.%, 7.5 vol.%, and 10 vol.%, the relative densities reach to 87.6%, 91.5%, 97.0%, and 99.9%, respectively. The relative density results are consistent with the fracture morphologies shown in Figure 3, confirming that the addition of Y2O3 contributes to the compactness of the SiC/SiCw-Y2O3 composite ceramics. It’s worth noting that the poor compactness of Y000 reveals the formula failed when sintering in this process condition; therefore, many valid mechanical and tribological data cannot be obtained. For example, although the Vickers hardness of Y000 was obtained, it was only 1.3 GPa and at least an order of magnitude smaller than the other groups. Hence, the Y000 group was abandoned in subsequent tests. Compare the Y000 specimen with the other 4 groups containing Y2O3, confirming that Y2O3 additives have a noticeable promoting effect on the microstructure and mechanical properties of SiC composite ceramics. With the Y2O3 content increasing from 2.5 vol.% to 7.5 vol.%, the Vickers hardness increases from 10.9 GPa to 21.6 GPa, then decreases to 18.9 GPa when Y2O3 content is 10 vol.%. The results indicate that suitable Y2O3 content (≤7.5 vol.%) can increase the Vickers hardness, and excessive Y2O3 content (10 vol.%) can weaken the Vickers hardness. Similar variations can be found in the fracture toughness (Figure 6c) and flexural strength results (Figure 6d). The values increase when Y2O3 content increases from 2.5 vol.% to 7.5 vol.% and then decrease when Y2O3 content reaches 10 vol.%. Of course, although the tested mechanical properties of Y100 are not the best, it is still slightly better than Y050 and Y025, proving that excessive Y2O3 does not significantly deteriorate the relevant performance dramatically. The hampered mechanical properties of Y100 are strongly affected by their microstructure since the aggregated Y2O3 can decrease its load-bearing capacity attributed to the poorer mechanical properties of Y2O3 compared with SiC [37]. Besides, the excessive Y2O3 made redundant liquid phase connect in a larger potential flaw fracture origin [26].
Seo et al. [19] reported the SiC-2 vol.%Y2O3 ceramic which was fabricated by hot-press sintering at 2000 °C, 40 MPa, N2 for 3 h. The relative density, fracture toughness, and flexural strength are 99.1%, 3.4 MPa · m1/2, and 586 MPa, respectively. SiC-2 vol.%Y2O3 ceramic shows slightly higher relative density and flexural strength than SiC/SiCw-7.5 vol.%Y2O3 composite ceramic (Y075) sintered at 1800 °C in this study. Both studies indicate that Y2O3 can improve the densification of the as-sintered ceramics, and the SiC composite ceramics with an appropriate amount of Y2O3 can reduce the hot-pressed sintering temperature to a comparatively lower one (1800 °C). Furthermore, compared with Y075, the fracture toughness of SiC-2 vol.%Y2O3 ceramics decreased by 55.8%. It can be speculated that the SiCw reinforced [6,7,8,9] and the Y2O3 pinned in [25] can both improve the mechanical properties, particularly the fracture toughness of the SiC composite ceramics. It can be concluded that incorporated Y2O3 and SiCw can work together to improve the compactness of microstructure and the mechanical performance of the SiC composite ceramics.
The COF variations of SiC/SiCw-Y2O3 composite ceramics with sliding time are displayed in Figure 7a. In all groups, the COF sharply rises at the initial stage, then decreases and shows a relatively stable status after sliding for ~200 s. After contact with each other, the asperities on SiC/SiCw-Y2O3 composite ceramic and YG6 ball increase the contact stress between them so that a considerable COF value can be obtained. After the run-in stage, the relatively stable COF indicates that the contact surface of the specimen and ball increases, indicating the decreased surface roughness of the grinding bodies. Although the COF at the stable stage does not change dramatically, slight increases of COF in groups with lower contents (Y025 and Y050) can still be seen. The average COF of Y025, Y050, Y075, and Y100 during the sliding period are 0.36, 0.35, 0.34, and 0.32, respectively, indicating that incorporating Y2O3 can decrease the COF of SiC/SiCw-Y2O3 composite ceramics. Combined with the formula of SiC/SiCw-Y2O3 composite ceramics, it can be boldly speculated that the worn Y2O3 debris can more easily fill the pits of the wear scars than SiC and SiCw, reduce the roughness, and thus slightly reduce the COF. The COF and antifriction effect of Y2O3 is positively correlated with its content [37,40,41,42].
Figure 7b depicts the wear track profiles of SiC/SiCw-Y2O3 composite ceramics. It can be seen both the width and depth of the wear track of composite ceramics decrease in groups with Y2O3 content ≤7.5 vol.%. As the Y2O3 content continues to increase, the width and depth of the wear track of Y100 increase, but it is still smaller than Y050. Besides, the wear scar profiles of Y075 and Y100 are smoother than Y025 and Y050, indicating the more compact microstructure and better mechanical properties of the latter groups. Figure 7c1–c4 vividly displays the 3D morphology of the wear track on each sample surface. These images exhibit the depth and width of the wear track (consistent with Figure 7b) and can reveal the surface roughness inside the wear track. As can be seen, the wear tracks of Y025 and Y050 possess larger roughness than Y100 and Y075, and the Y075 is the smallest. Generally, in the case of the same materials type, the smoother the surface, the lower the friction coefficient, and the better the wear resistance [43,44].
The maximum depth, width, wear volume, and specific wear rate of the wear track of SiC/SiCw-Y2O3 composite ceramics are listed in Table 1. The maximum depth and width are consistent with the results of 2D and 3D profiles in Figure 7b,c1–c4. Moreover, with Y2O3 content increasing from 2.5 vol.% to 7.5 vol.%, the wear volume and specific wear rate reach the lowest value of 3.82 × 10−3 mm3 and 1.59 × 10−5 mm3/(N · m). As the Y2O3 content continues to increase, the wear volume and specific wear rate slightly increase but are still lower than the Y050 group. Thus, it can be concluded that high Y2O3 addition can reduce the COF, and Y2O3 additives can significantly improve the wear resistance of SiC/SiCw-Y2O3 composite ceramics. SiC composite ceramics with 7.5 vol.%Y2O3 shows the best wear resistance than others.
SEM images of wear scars reveal the correlation between the microstructure and wear resistance. As shown in Figure 8, the surface morphologies of wear scars (first line) are in accordance with the 3D profiles shown in Figure 7c1–c4. As for Y025, flaky debris does not connect tight in the microscale covered on the wear scar surface. This morphology was caused by the cold-welded debris onto the edge of the SiC. The flaky debris filled the holes of the hot-pressed ceramic, but due to the low friction heat and insufficient quantity, they do not have tight bonding with the substance below [43]. Meanwhile, the asperities bear greater friction and lead to worse wear resistance. The wear morphology and mechanism of Y050 are similar to that of Y025, but the wear surface of Y050 is mildly flat, and the wear resistance is improved over Y025 due to the increased relative density. Adding Y2O3 up to 7.5 vol.% and 10 vol.% further improves the relative density of composite ceramics, but excessive Y2O3 aggregated around SiC and SiCw (especially Y100) weakens the Vickers hardness and the subsequent wear resistance [27,45]. As seen in Figure 8c2,d2, no sintering holes exist in Y075 and Y100, but the size of cracks in Y100 is larger than in Y075, indicating poor mechanical properties of Y100. The lower hardness of Y2O3 than SiC is also responsible for the decreased wear resistance of Y100 [37]. Y075 group possesses the optimal wear resistance, and the abrasive wear plays an important role, as evidenced by smooth wear scar surfaces and long and thin furrows. The specific wear rate of Y075 is 11.8% than Y025.

4. Conclusions

SiC/SiCw-Y2O3 composite ceramics with 10 vol.% SiCw and different Y2O3 contents were fabricated by hot-pressed sintering at 1800 °C. The effects of Y2O3 content on the microstructure, mechanical properties, and tribological behaviors were systematically investigated. It is found that compact SiC/SiCw cannot be hot-pressed without Y2O3 additives at 1800 °C and 40 MPa. With Y2O3 content increase, the microstructures are getting compact with increased relative density, but excessive Y2O3 leads to its aggregation. Moreover, with Y2O3 content increasing from 2.5 vol.% to 7.5 vol.%, the Vickers hardness, fracture toughness, and flexural strength all increase to the optimal values. As Y2O3 content increased to 10 vol.%, those properties were slightly reduced. Due to the compact microstructure, proper Y2O3 content, and excellent mechanical properties, SiC/SiCw-7.5 vol.%Y2O3 ceramic (Y075) shows optimal wear resistance. The specific wear rate of Y075 is 11.8% of that for Y025 (SiC/SiCw-2.5 vol.%Y2O3 ceramic). The excellent mechanical properties and good wear resistance of Y075 highlight its potential future application.

Author Contributions

Conceptualization, J.W. and L.Z.; methodology, S.Z. and J.W.; software, S.Z. and L.D.; validation, S.Z. and H.C.; formal analysis, X.L. and F.W.; investigation, Z.T., L.S. and S.C.; resources, L.Z.; data curation: S.Z.; data interpretation: S.Z. and S.D. writing—original draft preparation, M.Z., J.W. and S.Z; writing—review and editing, M.Z., J.W. and L.Z.; visualization, N.Y.; supervision, S.D.; project administration, L.Z. and S.C.; funding acquisition, L.S., N.Y. and L.Z. All authors have read and agreed to the published version of the manuscript.

Funding

The authors would like to acknowledge the National Natural Science Foundation of China (No. 21671145 and No. 52201187), the Zhejiang Province key research and development plan project (2023C01082), the General Scientific Research Project of Zhejiang Provincial Education Department (No. Y202249336), the Natural Science Foundation of Zhejiang Province (LQ19E050004), the Agricultural Science and Technology Key R & D Program of Taizhou (NYJBGS202201).

Institutional Review Board Statement

This article does not need ethical approval.

Informed Consent Statement

This article does not involve human experiments.

Data Availability Statement

Data are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare no conflict of interest.

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Coatings 13 00956 g001 550
Figure 1. SEM images of (a) SiC powder, (b) SiCw powder, (c) Y2O3 powder, and (d) the XRD patterns of the raw powders.
Figure 1. SEM images of (a) SiC powder, (b) SiCw powder, (c) Y2O3 powder, and (d) the XRD patterns of the raw powders.
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Figure 2. The schematic diagram of the sintering procedure.
Figure 2. The schematic diagram of the sintering procedure.
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Figure 3. The fracture morphologies of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents. (a) Y000; (b) Y025; (c) Y050; (d) Y075; (e) Y100. The yellow arrow indicates SiCw or its location after being pullout.
Figure 3. The fracture morphologies of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents. (a) Y000; (b) Y025; (c) Y050; (d) Y075; (e) Y100. The yellow arrow indicates SiCw or its location after being pullout.
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Figure 4. The PDBSE images and EDS point scan results of SiC/SiCw-Y2O3 composite ceramics. (a–c) Y075, (d–f) Y100. Points 1 and 3 indicate the lighter grayscale area, and points 2 and 4 indicate the darker grayscale area on the polished morphologies.
Figure 4. The PDBSE images and EDS point scan results of SiC/SiCw-Y2O3 composite ceramics. (a–c) Y075, (d–f) Y100. Points 1 and 3 indicate the lighter grayscale area, and points 2 and 4 indicate the darker grayscale area on the polished morphologies.
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Figure 5. XRD patterns of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents.
Figure 5. XRD patterns of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents.
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Figure 6. The variations of (a) relative density, (b) Vickers hardness, (c) fracture toughness, and (d) flexural strength of SiC/SiCw-Y2O3 composite ceramics.
Figure 6. The variations of (a) relative density, (b) Vickers hardness, (c) fracture toughness, and (d) flexural strength of SiC/SiCw-Y2O3 composite ceramics.
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Figure 7. (a)The coefficient of friction, (b) the 2D, and (c1–c4) the 3D wear track profile of SiC/SiCw-Y2O3 composite ceramics after grinding with YG6 balls at 20 N for 20 min: (c1) Y025; (c2) Y050, (c3) Y075, (c4) Y100.
Figure 7. (a)The coefficient of friction, (b) the 2D, and (c1–c4) the 3D wear track profile of SiC/SiCw-Y2O3 composite ceramics after grinding with YG6 balls at 20 N for 20 min: (c1) Y025; (c2) Y050, (c3) Y075, (c4) Y100.
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Figure 8. The SEM morphologies of the wear track of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents. (a1,a2) Y025; (b1,b2) Y050; (c1,c2) Y075; (d1,d2) Y100. The yellow-dotted polygon outlines the sintering holes filled with wear debris.
Figure 8. The SEM morphologies of the wear track of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents. (a1,a2) Y025; (b1,b2) Y050; (c1,c2) Y075; (d1,d2) Y100. The yellow-dotted polygon outlines the sintering holes filled with wear debris.
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Table
Table 1. The maximum depth, maximum width, wear volume, and specific wear rate of the wear track of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents.
Table 1. The maximum depth, maximum width, wear volume, and specific wear rate of the wear track of SiC/SiCw-Y2O3 composite ceramics with different Y2O3 contents.
Maximum Depth
(mm)		Maximum Width
(mm)		Wear Volume (mm3)Specific Wear Rate
(mm3/(N · m))
Y0252.63 × 10−27.30 × 10−13.25 × 10−21.35 × 10−4
Y0501.25 × 10−25.01 × 10−17.74 × 10−33.23 × 10−5
Y0757.44 × 10−34.09 × 10−13.82 × 10−31.59 × 10−5
Y1008.23 × 10−34.51 × 10−16.46 × 10−32.69 × 10−5
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MDPI and ACS Style

Zhang, S.; Wang, J.; Zhang, M.; Ding, L.; Chan, H.; Liu, X.; Wu, F.; Tu, Z.; Shao, L.; Ye, N.; et al. Mechanical and Tribological Behaviors of Hot-Pressed SiC/SiCw-Y2O3 Ceramics with Different Y2O3 Contents. Coatings 2023, 13, 956. https://doi.org/10.3390/coatings13050956

AMA Style

Zhang S, Wang J, Zhang M, Ding L, Chan H, Liu X, Wu F, Tu Z, Shao L, Ye N, et al. Mechanical and Tribological Behaviors of Hot-Pressed SiC/SiCw-Y2O3 Ceramics with Different Y2O3 Contents. Coatings. 2023; 13(5):956. https://doi.org/10.3390/coatings13050956

Chicago/Turabian Style

Zhang, Shaohua, Jinfang Wang, Meng Zhang, Longqi Ding, Huijun Chan, Xiyu Liu, Fengqing Wu, Zhibiao Tu, Ling Shao, Nengyong Ye, and et al. 2023. "Mechanical and Tribological Behaviors of Hot-Pressed SiC/SiCw-Y2O3 Ceramics with Different Y2O3 Contents" Coatings 13, no. 5: 956. https://doi.org/10.3390/coatings13050956

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