Dry lubrication with soft metals: The tribological behaviour of a thin film of cadmium rubbing on carbon steel

Abstract

Since cadmium has many properties which make it suitable for use as a solid lubricant, a thorough study of its behaviour on a modified pin-on-ring testing device with conformal mating surfaces was made. The subsurface temperature, friction force and wear depth were recorded simultaneously. Pins of fully annealed carbon steel C40 were used. The rings were successively coated by electroplating with nickel, copper and cadmium films to obtain good adhesion to the hard substrate and to minimize diffusion into the hard mating surface. Three velocities, 1, 0.5 and 0.1 m s −1, and two loads, 20 and 100 N, were selected to provide a range of test conditions. Sections of the tested specimens were observed using both an optical microscope and a scanning electron microscope. The persistence of cadmium between the rubbing surfaces at various sliding distances was investigated using X-ray analysis. The behaviour of successive nickel and copper films and nickel films was investigated to confirm the good lubrication and wear properties of cadmium especially under conditions of heavy working.