Effect of secondary carbides addition on the microstructure and mechanical properties of (Ti, W, Mo, V)(C, N)-based cermets

Abstract

(Ti, W, Mo, V)(C, N)-based cermets were prepared by mixing Mo 2C, WC and TaC with ultrafine (Ti, W, Mo, V)(C, N) powders, and then processed via a conventional P/M technique. The effect of Mo 2C, WC and TaC on the microstructure and mechanical properties of (Ti, W, Mo, V)(C, N)–8 wt.% Ni–7 wt.% Co systems was investigated. The Mo 2C content was varied from 0 to 10 wt.% and additive WC or TaC was added at a level of 5 wt.% with Mo 2C addition. The results show that the densification of (Ti, W, Mo, V)(C, N)–8 wt.% Ni–7 wt.% Co cermets was improved significantly by the addition of Mo 2C. With the increase of Mo 2C content, there is a coarsening tendency in the microstructure of (Ti, 20W, 15Mo, 0.2V)(C, N)–8Ni–7Co system, but the refinement for (Ti, 15W, 5Mo, 0.2V)(C, N)–8Ni–7Co. TaC addition decreases the density of (Ti, 15W, 5Mo, 0.2V)(C, N)–10Mo 2C–8Ni–7Co cermet and thus weakens its bending strength. (Ti, 15W, 5Mo, 0.2V)(C, N)–10Mo 2C–5WC–8Ni–7Co cermet has optimal mechanical properties: bending strength of 1999 MPa, hardness ( H v) of 1677 MPa and toughness of 9.95 MPa m 1/2 respectively by adding WC, which is due to its ultrafine and weak core/rim structure.