Effect of heating mode on sinterability of Fe-Ni steels

The present study examines the effect of heating mode on the densifcation, microstructure, and mechanical properties of iron-nickel steel with graphite and phosphorus addition. The compacts were sintered in conventional (radiatively-heated) and microwave (2.45 GHz, multimode) furnaces at 1120°C for 1 hour in forming gas (dissociated ammonia atmosphere, 95% N₂-5% H₂). The experimental results show that microwave sintered alloy has better properties compared with the conventionally sintered counterparts. Detailed analyses by using optical microscopy and scanning electron microscopy (SEM) reveal that microwave sintered sample has finer microstructure. SEM examination of the fractured surfaces indicate that a mixed mode fracture containing both, ductile and brittle types, is present in microwave sintered alloy, in contrast with the brittle fracture only in conventional sintered counterpart.