Replacement of conventionally complex processing for low alloy steel 20Cr2Ni4A by rare earth carburising at lower temperature

This paper deals with the effects of rare earth (RE) addition on the micros tructure and properties of 20Cr2Ni4A steel carburised at 860 degreesC. Comp ared with conventional 920 degreesC carburising and other complex treatment s, finer and more dispersed carbide precipitates formed in the surface laye rs. A superfine martensitic structure and a less residual austenite were ob tained by direct quenching after RE 860 degreesC carburising. The microstru cture exhibited a higher microhardness, a wear resistant surface layer, and it also led to an increase in impact toughness. In addition, the heat trea tment period for this steel was remarkably reduced by the replacement of co nventional complex treatments by RE 860 degreesC carburising. (C) 2001 IoM Communications Ltd.