Microstructure, mechanical properties and fracture behavior of NiCoCrTiAl and FeNiCoCr new alternative binders for WC based hardmetals

Abstract

Hardness and fracture strength of WC-Ni-Co-Cr-Ti-Al cemented carbides have been measured at room temperature in as-HIPed and solution-aged conditions. These treatments are applied to modify the size of gamma prime precipitates, which are intrinsically formed within the metallic binder of these ceramic-metal composites during the sintering process. Compositions containing approx. 28-29 vol% metal content exhibit hardness values in the range of those reported for similar grades of WC-Co hardmetals. Optimized aluminum additions lead to materials with fracture strength values only 15% lower than those reported for the same WC-Co commercial references. These results suggest gamma prime precipitation hardening as a potential strategy for improving the performance of WC-Co materials at high temperatures.

Regarding Fe-Ni-Co-Cr alloys are potential candidates for partial substitution of Co content in WC-based hardmetals. It has been investigated WC coarse grade with 15 wt%(FeNiCoCr). The Cr content has been adjusted in order to avoid the precipitation of M7C3 carbides. Within the corresponding carbon windows, fracture strength values range from 2.8 GPa to 3.0 GPa. These values are within the range of standard WC-Co grades with similar binder contents and WC grain sizes.