INTERMETALLIC BONDED WC-BASED CERMETS BY PRESSURELESS MELT INFILTRATION

Several investigations have explored the use of Fe- and Ni-based alloy s as alternative metallic binders for Co in the WC-Co composites. Rece ntly, with the improved understanding of the mechanical properties of intermetallics, these were also considered as a possible replacement f or Co. Schneibel et al. have processed FeAl-WC composites to near full density (>99%), with intermetallic contents ranging from 40 io 60 vol % for applications requiring the excellent corrosion resistance of FeA l and wear resistance of WC. In this investigation, FeAl bonded tungst en 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 co nventional liquid phase sintering, leading to improvements in the hard ness and bend strength values. The technique has also been demonstrate d to work successfully in the processing of Ni3Al-bonded WC cermets. T ypical microstructures and preliminary mechanical properties are repor ted and discussed. Mechanical property data of Ni3Al/WC suggest that t he interfacial bond strength and the fracture toughness may be control led by alloying. Although bulk FeAl has a much lower ductility than bu lk Ni3Al, the similarity of the fracture toughness data for FeAl/WC an d Ni3Al/WC suggests that the fine FeAl ligaments in these composites h ave high ductilities, consistent with SEM observations. (C) 1997 Elsev ier Science Limited.