Corrosion and tribological investigations of the B4C coatings rubbing against SiC ball for high relative humidity engineering application

Abstract

In present investigation, we evaluated the corrosion resistance of the B4C coating by the potentiodynamic polarization tests. Compared with the 304 L steel substrate, the B4C coatings deposited by unbalanced magnetron sputtering technology exhibited excellent corrosion resistance. Furthermore, we systematically tested the B4C coatings rubbing against SiC ball under 85 % RH condition by a ball-on-disk tribometer with various normal loads and sliding speeds. The results showed that disc wear rates were maintained in the order of 10−7 mm3·N−1 m−1 and a much low friction coefficient (∼0.047) was achieved under 5 N and 0.07 m/s. In addition, the tribological performances of B4C coating rubbing against SiC ball under 85 % RH were better than those of DLC/SiC friction pairs. This is mainly due to the formation of a thin tribo-chemical film containing boric acid with passivated edges sites and silica gel on the sliding interface. According to SEM results, the wear mechanism for the B4C coating was also analyzed.