Sub-zero treatments of AISI D2 steel: Part II. Wear behavior

Wear behavior of AISI D2 steel specimens subjected to varied sub-zero treatments, namely: cold treatment, shallow cryogenic treatment and deep cryogenic treatment have been studied with respect to that of the conventionally heat treated ones. The wear behavior has been assessed by dry sliding wear tests under varying normal loads as well as by detailed characterizations of worn surfaces, subsurfaces and wear debris. The obtained results reveal that sub-zero treatments improve the wear resistance of the selected steel; the degree of improvement varies in the ascending order of cold treatment, shallow cryogenic treatment and deep cryogenic treatment, and is function of normal load. The operative mechanism of wear under the investigated conditions is severe delamination and the process of wear is found to proceed with the formation of white layer followed by its delamination, governed by the associated extent of plastic deformation of subsurface. The wear rates are governed by the type of sub-zero treatments and the wear test conditions, and these are in conformity with the characteristics of the worn surfaces, subsurfaces and generated wear debris. The overall wear behavior of the specimens has been explained on the basis of their microstructural characteristics and hardness values, which are detailed in the companion paper (part I).