Alloying of sinter hardening PM steels through the masteralloy route – A comparison to commercial PM grades

The masteralloy (MA) approach is an increasingly attractive alloying route for introducing elements into sintered steels. This holds in particular for elements such as Cr, Mn and Si, which are oxygen-sensitive but cheap and non-strategic. In the present study, MAs containing these elements were added to plain Fe base powder, and sintering was performed at 1150 and 1180°C, respectively, with subsequent sinter hardening. It showed that compared to the commercial grade Distaloy DH-1, the MA grades benefited from higher sintering temperature as well as from lower carbon content of 0.6% nominal. At 0.75%C, dissolution esp. of Cr containing MAs is retarded by formation of carbides. Compared to the reference material, the MA variants did not result in fully martensitic microstructures, which however may not be mandatory in service since the sintering contacts are preferentially strengthened. In general, the MA approach was found to require less and cheaper alloy elements to attain attractive hardness-toughness combinations.