Microstructure and Mechanical Properties of NbC Matrix Cermets Using Ni Containing Metal Binder

摘要

The current study reports on the effect of the addition of Al metal and secondary refractory carbides onthe microstructure and mechanical properties of Ni bonded NbC matrix cermets. Powder mixtureswere pressurelessly sintered for 1 h at 1420℃ in vacuum. Microstructural and elemental mapping ofthe sintered cermets were performed by electron probe microanalysis (EPMA) to reveal the effect ofthe additions on the NbC grain morphology, grain growth and binder composition. Results indicatedthat NbC grain growth was suppressed and a homogeneous NbC grain size distribution was obtainedin the cermets with the addition of Al and secondary carbides, i.e. Mo_2C + VC + WC, as compared tothe pure Ni binder. The liquid phase sintered NbC-12 vol% Ni cermet had a Vickers hardness (HV_(10)) of1130 ± 22 kg/mm~2 and indentation toughness of 11.8 ± 0.4 Mpa m~(1/2). With the addition of 4 vol% WC-4 vol% VC-4 vol% Mo_2C, the hardness increased to 1490 ± 15 kg/mm~2, whereas the correspondingtoughness decreased to 9.2 ± 0.4 Mpa m~(1/2). Addition of 4 vol% Mo_2C into WC-13.8 vol% Ni-52.3 vol%NbC mixture further increased the hardness to 1620 ± 19 kg/mm~2 in combination with a moderatefracture toughness of 7.7 ± 0.2 Mpa m~(1/2).