Role of Eta-carbide Precipitations in the Wear Resistance Improvements of Fe-12Cr-Mo-V-1.4C Tool Steel by Cryogenic Treatment

Abstract

The wear resistance of an Fe-12.2wt%Cr-0.84wt%Mo-0.43wt%V-1.44wt%C alloy tool steel after cold treatment at 223 K (subzero treatment) and after cryogenic treatment at 93 K (ultra-subzero treatment) has been investigated. The wear resistance of steels after cryogenic treatment is superior to that after cold treatment. The effects of cryogenic treatment on the microstructure were also studied by means of X-ray diffraction and transmission electron microscopy methods. Unlike cold treatment, cryogenic treatment improves the preferential precipitation of fine η-carbides instead of ε-carbides. These fine carbide particles enhance the strength and toughness of the martensite matrix and then increase the wear resistance. The formation mechanism of fine η-carbide is discussed. © 1994, The Iron and Steel Institute of Japan. All rights reserved.