WC-Fe Alloys as Stress Relief Layer Materials for Sinter-Bonding between Cemented Carbides and Steels

Abstract

The applicability of sintered WC-Fe alloys as stress relief layer materials for the sinter-bonding method of cemented carbide and carbon steel has been basically discussed. The structure and mechanical properties of sintered WC-(20-40mass%)Fe alloy compacts were investigated. These WC-Fe alloys compacts sintered at 1553K or higher showed complete densification. η phase (Fe₃W₃C) particles which were coarser than the tungsten carbides particles were formed in the sintered compacts, and also fine pearlite structure were formed in binder metal parts. Though the hardness of sintered compacts were almost independent of sintering temperature being higher than 1553K, the fourpoint bending strength decreases with the increase of sintering temperature. It may be caused by coarsening of rl phase particles. Therefore the restraint in growth of rl phase particles in the WC-Fe alloys is effective for the high bonding strength. Coefficient of thermal expansion α (K^-1) between 303 and 973K for the compacts sintered at 1553K was given by α=(0.093V_Fe+4.12)×10_-6, where V_Fe is volume percent of iron powder.