Effect of alloying elements and processing factors on the microstructure and hardness of sintered and induction-hardened Fe-C-Cu alloys

The SC 100.26 iron powder and the PASC 60 powder (with a P content of 0.6 wt%) were mixed with graphite and copper powders. The blended powder mixtures were compacted, sintered and the P-containing sintered alloys were then induction-hardened. Experimental results show that the microstructure of sintered Fe-C-Cu alloys varies with the copper content. The proeutectoid ferrite becomes refined and decreases in volume when the copper content is increased. The ferritic phase is markedly hardened by the dissolved copper. The P-containing specimens exhibit marked volume expansion following sintering. The volume dilation increases with increasing compacting pressure. The hardness of sintered Fe-C-Cu-P alloys increases with increasing compacting pressure and carbon content. Further strengthening is resulted from the strong solution hardening effect of phosphorus in iron. Hardness variation of sintered alloys, with the carbon content, is dependent on the compacting pressure. Following induction hardening the surface hardness also increases with increasing carbon content and compacting pressure, but by a different mode from that in the as-sintered state. This is promoted by the phosphorus addition.