Correlation of microstructure with wear behaviour of deep cryogenically treated AISI D2 steel

This study aims to reveal the underlying mechanisms responsible for the enhancement of wear resistance of AISI D2 steel by deep cryogenic treatment (DCT) through in-depth microstructural analyses, and thereby attempt to correlate microstructure with wear behaviour of DCT specimens with reference to that of conventional heat treatment (CHT) and cold treatment (CT). Microstructural characterizations of the differently treated specimens have been done by image analyses of optical and SEM photographs, XRD, and EDX analyses, whereas wear behaviour has been characterized by wear rate, wear resistance, and analyses of worn surfaces, wear debris and subsurfaces. The results indicate that DCT markedly enhances the wear resistance of the selected steel compared to CHT and CT. Formation of white layer and its subsequent delamination have been identified as the operative wear mechanisms; the extent of these phenomena and the consequent wear rate is dependent on the type of treatment that determines the microstructures. The wear behaviour can be unambiguously correlated with the modifications in the precipitation behaviour of secondary carbides and reduction in the retained austenite content of the microstructure, which are the governing mechanisms for the improved of wear resistance of tool steels by DCT.