Preparation of ultra-fine grain WC-10Co cemented carbide by two-step sintering

Abstract

In this work, the ultra-fine grain WC-10Co alloys were prepared through a two-step sintering process comprising steps of low-temperature sintering for a long time and high-temperature sintering for a short time. The effects of sintering methods (one-step/two-step sintering) on the microstructure, density, grain size and performance of WC-10Co hard metals with or without VC addition were investigated. The densities of all samples were lower than 97.0% in one-step sintering. After two-step sintering, the relative densities of all samples were increased, and those of the samples without VC were higher than 98.5%. In addition, there are a large number of grains with a high aspect ratio in the samples without VC. The pure WC-10Co alloy showed the best comprehensive mechanical properties after long-time (2 hours) sintering at a low temperature (1300 °C) and short-time (10 minutes) sintering at a high temperature (1450 °C), and the grain size, hardness and toughness of the sample were 0.70 μm, 15.35 GPa and 13.54 MPa·m 1/2 , respectively. The grain size of the sample containing 0.5 wt.% VC was only 0.26 μm under the same sintering conditions, which showed a high hardness of 18.14 GPa and a toughness of 8.56 MPa·m 1/2 .