Intermetallic bonded WC-based cermets by pressureless melt infiltration

Abstract

Abstract Several investigations have explored the use of Fe- and Ni-based alloys as alternative metallic binders for Co in the WCCo composites. Recently, with the improved understanding of the mechanical properties of intermetallics, these were also considered as a possible replacement for Co. Schneibel et al. have processed FeAlWC composites to near full density (>99%), with intermetallic contents ranging from 40 to 60 vol% for applications requiring the excellent corrosion resistance of FeAl and wear resistance of WC. In this investigation, FeAl bonded tungsten carbide cermets with intermetallic contents from 10–30 vol% (about 4–14 wt%) were successfully processed with densities greater than 98.5% by a simple and economical melt infiltration process. The densities of these composites are significantly higher than those obtained by conventional liquid phase sintering, leading to improvements in the hardness and bend strength values. The technique has also been demonstrated to work successfully in the processing of Ni3Al-bonded WC cermets. Typical microstructures and preliminary mechanical properties are reported and discussed. Mechanical property data of Ni3Al/WC suggest that the interfacial bond strength and the fracture toughness may be controlled by alloying. Although bulk FeAl has a much lower ductility than bulk Ni3Al, the similarity of the fracture toughness data for FeAl/WC and Ni3Al/WC suggests that the fine FeAl ligaments in these composites have high ductilities, consistent with SEM observations.