Sintering behavior of NbC based cemented carbides bonded with M2 high speed steel

Abstract

Densification behavior of NbC-12 wt.% M2 high speed steel (HSS) cemented carbide was studied using a thermo-mechanical analyzer. To be able to survey the complete sintering process, model-free and model-based kinetic analysis were combined. According to this approach, the sintering process was divided into two main parts. The first part is associated with high shrinkage and according to the model-free analysis, three steps can be identified in this part. In the second part, the presence of solution-reprecipitation can be identified according to the developed models for liquid phase sintering. By dividing the sintering behavior into two main parts, it is possible to overcome the effect of limited NbC solubility in Fe during the heating process. This effect can be observed in the densification curves as a slight expansion at the end of the first sintering part. It is assumed that poor wetting performance at low temperatures results in the outflow of the liquid phase to the surface of the compacts which results in a fake densification. It was evident that wetting performance improves significantly at elevated temperatures (above 1310 °C) inducing a re-infiltration of liquid drops on the surface inside the inner pores and the expansion in the shrinkage curve.