Friction-reduction Behavior of Sulfurized Layer on the Surface of a Carbon Steel Electrolytically Sulphurized at Room Temperature

A mild carbon steel disc was carbon nitrided at high temperature and then sulfurized at room temperature by means of room temperature electrolytic sulphurization. This is aimed at improving the friction reduction and wear resistant behavior of the steel. The friction behavior of the sulfurized layer on the steel surface was investigated on an MPX 200 friction and wear tester, by sliding the sulfurized steel disc against a pin made of a tool steel. The worn surface of the sulfurized steel disc was observed with a scanning electron microscope, while the chemical states and phase structure of carbon nitrided carbon steel and of the sulfurized one were examined by means of X ray photoelectron spectroscopy and X ray diffraction. As the results, the sulfide layer on the carbon steel surface is composed of FeS and functions to reduce friction and wear at relatively low load. The friction reduction and wear resistant behavior of the sulfide layer is greatly dependent on its thickness. Thus special attention should be given to selection of optimized sulfide layer thickness in engineering practice, so as to acquire desired tribological modification effect of the carbon steel.