On the Wear Resistance of High Speed Steel of the White Layer Formed by Vacuum Oil-Quenching

Abstract

A white layer is formed on the vacuum oil-quenched high speed steel. The vacuum oil-quenched SKH-9 was rubbed against SUJ-2 in a dry condition by the use of an Ogoshi rapid wear testing machine to clarify the wear resistance of high speed steel on which the white layer was formed.
The formation of the white layer tended to improve the wear resistance of the high speed steel at sliding speeds in excess of 2.0 m/s. As the thickness of the white layer increased, the wear loss decreased, in general. In improvement of the wear resistance, were three types as follows: In the case of the white layer that consists of a large amount of retained austenite and a small amount of M₆C-type carbide as well as martensite, (1) Under light loads the white layer showed higher resistance to wear by itself. (2) Under heavy loads wear rates decreased rapidly as soon as the rotor reached the white layer-matrix boundary. It seemed that the white layer between the rotor and the matrix was effective as lubricant. The thinner layers were less effective. (3) In the case of the thicker layers, the carbide layers which perhaps consisted of M₃C, M-C, and M₂C-type carbide were formed. The carbide layers had high hardness as well as high resistance to decomposition on heating. Consequently, the carbide layers gave the improved resistance to wear all over the range of load tested.