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This article focuses on the microstructural evolution and wear behavior of 50wt%WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. The microstructure and chemical composition of the coatings were investigated by X-ray diffraction(XRD), differential thermal analysis(DTA), scanning and transmission electron microscopy(SEM and TEM) equipped with energy-dispersive X-ray spectroscopy(EDS). The wear resistance of the coatings was tested by thrust washer testing. The mechanisms of the decomposition, dissolution, and precipitation of primary carbides, and their influences on the wear resistance have been discussed. The results indicate that the coating sintered at 1175 oC is composed of fine WC particles, coarse M6C(M=Ni, Fe, Co, etc.) carbides, and discrete borides dispersed in solid solution. Upon increasing the sintering temperature to 1225 oC, the microstructure reveals few incompletely dissolved WC particles trapped in larger M6 C, Cr-rich lamellar M23C6, and M3C2 in the austenite matrix. M23C6 and M3C2 precipitates are formed in both the γ/M6 C grain boundary and the matrix. These large-sized and lamellar brittle phases tend to weaken the wear resistance of the composite coatings. The wear behavior is controlled simultaneously by both abrasive wear and adhesive wear. Among them, abrasive wear plays a major role in the wear process of the coating sintered at 1175 oC, while the effect of adhesive wear is predominant in the coating sintered at 1225 oC.
This article focuses on the microstructural evolution and wear behavior of 50 wt% WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. The microstructure and chemical composition of the coatings were investigated by X-ray diffraction (XRD Differential thermal analysis (DTA), scanning and transmission electron microscopy (SEM and TEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The wear resistance of the coatings was tested by thrust washer testing. The mechanisms of the decomposition , dissolution, and precipitation of primary carbides, and their influences on the wear resistance have been discussed. The results indicate that the coating sintered at 1175 oC is composed of fine WC particles, coarse M6C (M = Ni, Fe, Co, etc. ) carbides, and discrete borides dispersed in solid solution. Upon increasing the sintering temperature to 1225 oC, the microstructure reveals few incompletely dissolved WC particulars M23C6 and M3C2 in the austenite matrix. M23C6 and M3C2 precipitates are formed in both the γ / M6 C grain boundary and the matrix. These large-sized and lamellar brittle phases tend to weaken the wear resistance of the composite coatings. The wear behavior is controlled simultaneously by both abrasive and adhesive wear. Among them, abrasive wear plays a major role in the wear process of the coating sintered at 1175 oC, while the effect of adhesive wear is predominant in the coating sintered at 1225 oC.