High performance tin-based Babbitt coatings deposited by high-pressure cold spraying

Abstract

Tin-based Babbitt alloys are widely used as sliding bearing materials due to their excellent tribological properties such as good friction reduction, friction resistance and embeddedness. In this study, for the first time, tin-based Babbitt coatings (SnSb11Cu6) were deposited on 40Cr steel substrates by a high-pressure cold spraying system with dual downstream injection as a preliminary investigation of anti-friction coatings for sliding bearings. The effects of process parameters on deposition efficiency, microstructure, microhardness, bond strength and tribological properties of cold sprayed SnSb11Cu6 coatings were systematically investigated. Results showed that with the optimization of process parameters, deposition efficiency tends to increase first and then decrease, and the optimal deposition efficiency achieved is 53 %. The coating prepared at the gas pressure of 1.5 MPa and gas temperature of 450 °C has the highest density, and the best overall mechanical and tribological properties. XRD results showed that no phase change and oxidation occurred for coatings under all cold spraying conditions. The highest microhardness of cold sprayed SnSb11Cu6 coatings is 28.8 HV0.05, higher than that of as-cast alloy (~22.5 HV0.05). The bond strength between SnSb11Cu6 coatings and the steel was significantly increased by using bond coat and is highest as 21 ± 3 MPa. The lowest coefficient of friction and wear rate of the SnSb11Cu6 coatings is 0.23 and 7.99 × 10−5 mm3/N·m, respectively (pair: GCr15 ball, 3 N). The deposition mechanisms and wear mechanisms of cold sprayed SnSb11Cu6 coatings were also analyzed. With the optimization of process parameters, the particle physical state transits from semi-molten to fully-molten, and the bonding mechanism is mainly mechanical interlocking. The wear mechanisms of cold sprayed SnSb11Cu6 coatings are abrasive wear and adhesive wear, and abrasive wear dominates.