Dissolving mechanism of the WC/W₂C_P in NiCrBSi alloy and surface modification for the WC/W₂C_P by carburizing

In order to restrain the excessive dissolving of the cast tungsten carbide particles (WC/W₂C_P) used in the production of composites, the dissolving mechanism of the WC/W₂C_P in NiCrBSi alloy and the surface modification for the WC/W₂C_P by carburizing were investigated by SEM, EDS, XRD etc. The results show that the cast tungsten carbide consists of WC and W₂C, and WC has a higher chemical resistance in molten NiCrBSi than W₂C. Interdifusion of elements occurred between the molten matrix and the particles during the preparation of WC/W₂C_P reinforced NiCrBSi composite coating by fusion sintering. W₂C in WC/W₂C_P reacted with Ni, Cr and other elements diffusing from molten matrix to form W, Ni-rich carbides, while WC in WC/W₂C_P remained mostly intact. Elements such as Ni and Cr in matrix reacted with W and C diffusing from WC/W₂C_P to form W, Ni, Cr-rich carbides and precipitated from the melt during cooling. After carburization, the cast tungsten carbide particles had a shell of WC, which can effectively restrain dissolving of the particles, and reduce carbide precipitations in the matrix.