Dual‐grained (Ti, W)C–Ni cermets by two‐step carbonization: Hot isotropic press sintering of NiTiW alloys and colloidal graphite

Abstract

Reactive sintering of crushed metals and carbon is advantageous for preparing toughened complete solid-solution cermets (CSCs). Here, dual-grained (Ti 0.6 , W 0.4 )C-18Ni cermets were prepared using a two-step carbonization method. High-energy milling of Ni-Ti-W-C (Ni(Ti 0.6 , W 0.4 ) 4 C) mixture afforded NiTiW solid solution, which was then transformed into Ni 6 W 6 C by heating at 1250°C.Twinned (Ti, W)C platelets were formed by the carbonization of Ni 2 W 4 C during liquid sintering. W atoms that accumulated in the (111) planes of TiC promoted the {111} twin formation, leading to sandwich-type (Ti, W)C platelets. Dense (Ti 0.6 , W 0.4 )C-18Ni cermets were obtained by hot isostatic press sintering in Ar with satisfactory Hv of 12.8 ± 0.2 GPa, high strength of 1960 ± 84 MPa and toughness of 15.80 ± 0.6 MPa·m 1/2 . A higher sintering temperature or graphite content accelerated the carbonization, resulting in coarser platelets with decreased aspect ratio. This study provides a new approach to modify the microstructure of CSCs and a method for preparing dual-grained cermets.