Influence of Variations of the Steel Substrate-Cr sub 3 Si(Cr)/MoS sub 2- sub x Film System on Wear Properties

The film systems Cr sub 3 Si/MoS sub 1.85 and Cr/MoS sub 1.85 as low-friction composites on steel substrates were deposited by planar high frequency magnetron sputtering. The deposition conditions such as the sputtering parameters, operating gas pressure, target-substrate distance and substrate temperature were kept constant. The film thickness of the intermediate layers Cr sub 3 Si, Cr and MoS sub 1.85 was varied. Tribological investigations by scratch testing and pin-on-disc testing led to an optimum result for 100nm Cr sub 3 Si and 500-1000nm MoS sub 1.85 . For the system Cr/MoS sub 1.85 the optimum result was obtained for about 400nm Cr, and about double the value of MoS sub 1.85 . The friction coefficients mu in air measured by scratch testing lie between 0.03 and 0.07 and the critical loads L sub c reached values up to 25N. In the pin-on-disc tests pins of hard metal, Al sub 2 O sub 3 and 100Cr6 were used as counterpart. For the hard metal pairs numbers of revolution up to 60 000 and 40 000 were measured for Cr sub 3 Si/MoS sub 1.85 and Cr/Mo sub 1.85 respectively. The chemical composition of the layers was determined by ESMA and the in-depth homogeneity by Auger electron spectroscopy. X-ray measurements show very broad maxima, while transmission electron microscopy reveals crystallite sizes ranging from 2 to 6nm.