Tribological Studies on Deep Cryogenic Treated Aisi T42 High Speed Steel Using Response Surface Methodology

Abstract

High – speed steels are the most widely used tool material in small and medium scale industries, owing to their excellent toughness and economic price over their competitors. But the wear resistance and hot hardness of high-speed steels are poor compared to tools made out of carbides. Recent investigations, on the effect of cryogenic treatment have proved to be an alternative option to enhance the hardness and wear resistance of high-speed tool materials. But so far only a limited number of investigations have been made into the effect of cryogenic treatment on different grades of high-speed steels. The present research reports the effect of deep cryogenic treatment on AISI T42 grade high – speed steel, with specific emphasis on mode and mechanism of wear. Wear behavior has been studied using pin-on-disc tribo-meter under dry condition. Response surface methodology was adopted in designing the experiments for two factors with five levels. Mathematical model has been developed incorporating the effect of sliding velocity and load on the wear behavior. Sliding velocity was found to be dominant factor than normal load. Morphology of worn surface and the wear debris was studied using SEM to identify the mode and mechanism of wear. Mild oxidative wear was the dominant mode of wear throughout the range of variables used in this study. Deep cryogenically treated specimens exhibited significant improvement in wear resistance than conventionally heat treated specimens, especially at higher sliding velocities. The wear rate of conventionally heat treated specimen was found to be 3.138 to 2.493 times higher than that of deep cryogenically treated specimens. There was an increase in hardness value form 66.8-67.2 HRC at the end of conventional heat treatment to 69.5-70.2 HRC at the end of deep cryogenic treatment.