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为了抑制铸造碳化钨颗粒(WC/W2C P)在复合材料制备过程中的过度分解,利用SEM、EDS和XRD等测试手段对WC/W2C P在Ni Cr BSi合金中的分解机理及其表面改性渗碳处理进行了研究。结果表明,铸造碳化钨由WC和W2C两相组成,在Ni Cr BSi合金中WC相比W2C相具有更好的化学稳定性。在熔烧法制备WC/W2C P增强Ni Cr BSi基复合材料涂层的过程中,基体熔液和WC/W2C P发生元素互扩散;WC/W2C P中的化学稳定性差的W2C相与从基体熔液中扩散过来的Ni、Cr等元素反应生成了富W、Ni的碳化物,而化学稳定性好的WC相几乎完整的保留下来;基体中的Ni、Cr元素与从WC/W2C P中扩散过来的W、C元素形成了富W、Ni、Cr的碳化物在凝固过程中析出。经渗碳表面改性后,WC/W2C P表面形成了化学稳定性好的WC壳层,该壳层能有效抑制WC/W2C P在基体中的扩散分解,减少基体中碳化物的析出。
In order to suppress the over-decomposition of WC / WC2C particles in the preparation of composites, the decomposition mechanism and surface modification of WC / W2C P in Ni-Cr-BSi alloy were investigated by means of SEM, EDS and XRD. Carburizing treatment was studied. The results show that the cast tungsten carbide is composed of two phases, WC and W2C, and WC has better chemical stability than that of W2C in NiCr BSi alloy. In the process of preparation of WC / W2C P-reinforced NiCrBi-based composite coating by melt sintering, the matrix melt and WC / W2C P interdiffuse each other. The W2C phase with poor chemical stability in WC / The diffused Ni, Cr and other elements react to form W and Ni-rich carbides, while the chemically stable WC phase remains almost intact. The Ni and Cr elements in the matrix react with WC Diffusion of W, C elements formed rich W, Ni, Cr carbide precipitation during the solidification process. After carburizing surface modification, the WC / W2C P surface forms a WC shell with good chemical stability. The shell can effectively inhibit the diffusion and decomposition of WC / W2C P in the matrix and reduce the precipitation of carbides in the matrix.