Design of Sintered High Speed Steel Alloy Powders for Wear Applications

Abstract

High speed steel (HSS) powders of various compositions including some mixtures diluted with iron powder were compacted and sintered under a range of atmospheres. The aim was to assess the potential of the sintered materials for wear resistant components. The dependence of dimensional stability, mechanical properties, and microstructural development on processing parameters was investigated. It was found that adequate dimensional stability could be achieved after sintering at temperatures up to 1200°C. Above this temperature, dimensional instability occured due to the formation of a liquid phase. The mechanical properties of the compacts were improved by raising the sintering temperature and increasing sintering time. Above 1220°C, the presence of an excessive amount of liquid phase led to the development of grain boundary carbide networks in pure HSS samples and segregation of the carbide particles towards pore regions in diluted HSS compacts. In both cases this resulted in a sharp fall in bend strength. It was also observed that compositional homogenisation was slower than predicted in the HSSFe system. This phenomenon is explained in terms of the dissolution resistance of the carbide particles. PM/0531