Microstructures, Mechanical and Corrosion Properties of WC-(0-16) mass percent Cr_3C_2-15 mass percent Ni Cemented Carbides

摘要

Microstructures, some mechanical properties and electrochemical corrosive behavior of WC-(0-16)mass percent Cr_3C_2-15 mass percent Ni alloys were studied as a function of carbon and Cr_3C_2 contents of these alloys. It was found that solid solubility of Cr into y phase (Ni phase) of WC-Cr_3C_2-15 mass percent Ni alloy was about 2 percent and 4 mass percent Cr_3C_2 in high and low carbon alloys, respectively. In the range of the excess Cr_3C_2 content more than the solubility limit of Cr, some phases of WC+ gamma +M_2C+M_6C (theta) (M=(Cr,W,Ni), M_6C= theta phase), WC+ gamma +M_2C, WC + gamma +M_2C+M_3C_2, WC+ gamma +M_3C_2 to WC+ gamma +M_3C_2+FC appeared with increasing carbon content in the alloys. Hardness of the alloys increased with increasing the amount of Cr_3C_2. On the other hand, the transverse rupture strength reached the peak value at the solubility limit of Cr because of the finer grain size of WC by the effect of grain growth inhibition. More than the solubility limit of Cr, the transverse-rupture strength decreased with increasing the amount of Cr_3C_2, which was considered to be caused by crystallized M_xC_y acting as fracture source. On the anodic polarization curve in 3 percent NaCl solution, corrosive current density of these alloys decreased with increasing the amount of Cr_3C_2 within the solubility limit of Cr in y phase, but it was saturated more than the solubility limit of Cr.