Microstructures, Mechanical and Corrosion Properties of WC-(0-16)mass%Cr₃C₂-15mass%Ni Cemented Carbides

Abstract

Microstructures, some mechanical properties and electrochemical corrosive behavior of WC-(0-16)mass% Cr₃C₂-15 mass% Ni alloys were studied as a function of carbon and Cr₃C₂ contents of these alloys.
It was found that solid solubility of Cr into γphase (Ni phase) of WC-Cr₃C₂-15 mass%Ni alloy was about 2% and 4mass% Cr₃C₂ in high and low carbon alloys, respectively. In the range of the excess Cr₃C₂ content more than the solubility limit of Cr, some phases of WC+γ+M₂C+M₆C (θ) (M =(Cr, W, Ni), M₆C=θphase), WC+γ+M₂C, WC+γ+M₂C+M₃C₂, WC+γ+M₃C₂ to WC+γ+M₃C₂+FC appeared with increasing carbon content in the alloys.
Hardness of the alloys increased with increasing the amount of Cr₃C₂. 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 Cr₃C₂, which was considered to be caused by crystallized M_xC_y acting as fracture source.
On the anodic polarization curve in 3%NaCl solution, corrosive current density of these alloys decreased with increasing the amount of Cr₃C₂ within the solubility limit of Cr in yphase, but it was saturated more than the solubility limit of Cr.