Investigation on the synthesis mechanism and size control of (Ti,W,Mo,Cr)(C,N) solid solution powder

Abstract

Complex interfaces in cermets limit its application as cutting or heat-work die materials. Interface modification of hard particles by composition optimization is proved to be an effective strategy for high-performance Ti(C,N)-based cermets. Herein, we prepared (Ti,W,Mo,Cr)(C,N) solid solution powder through carbothermal reduction nitridation method. The phase and microstructure were characterized to discover the synthesis mechanism. Oxides of Mo, W, Ti, and Cr participated in the reaction successively, MoO2 transformed to M2X (X is C and/or N, M is W, Mo and/or Cr) directly, both W2C and W formed simultaneously as the reduction products of WO3, TiO2 followed TiO2 → TinO2n-1 → (Ti, M)(C,N) (M is W, Mo and/or Cr), and Cr diffused into (Ti, M)(C,N) and M2X phases directly from its oxide. Finally, the solid solution powder with composition (Ti0.83W0.07Mo0.09Cr0.01)(C0.62N0.38) in the particle size of 0.73 μm with ∼0.14 wt% oxygen and ∼ 0.43 wt% free carbon was obtained at 1750 °C for 2 h. Our findings provide insight into developing advanced cermets with better comprehensive properties.