Sintering behaviour of iron-molybdenum steels withtheadditionof Fe-B-C master alloy powders

Abstract

The effect of addition of Fe-B-C master alloy powders on the sintering behaviour of iron-molybdenum sintered steels has been investigated by dilatometric experiments. The addition ofthe Fe-B-C master alloy powders to the Fe-Mo-B-C sintered steels can activate the sintering process by liquid phase sintering. Liquid phases form owing to the reaction γ-Fe+ (Fe,Mo)₂B+Fe₃(B,C)• L at 1097°C and the reaction γ-Fe+Mo₂C+Fe₃C• L at 1085°C. The temperature of the liquid phase formation depends on the compositions and the amount of the master alloy powders. SEMQ analysis for the Fe-1·2Mo-0·4B-0·5C (wt-%) steelshows thatgrainboundary phasecontains approximately 5·0 wt-%Mo, much higher than that in the grains (approximately 0·95 wt-%Mo) and higher than that of the base powder Astaloy Mo (1·44 wt-%Mo). This means that molybdenum diffuses from particle to particle boundary to form borides and carbide during sintering.