The investigation of tribological properties of PAI/PI‐EPN polymer coating filled with WS₂ and SiC at low temperatures

Abstract

To improve the tribological properties of polar crane copper alloy bearings to withstand wear under dry sliding wear and grease lubrication at low temperatures, three kinds of coating materials modified by incorporating WS2 and SiC into polyamide‐imide/polyimide‐phenolic epoxy resin were designed. These composite coatings were sprayed on the surfaces of CuPb22.5Sn2.5 copper alloys by liquid spraying technique. Firstly, the tribological experiments were performed with three different coatings. Then, nanoindentation testing and wear morphology analysis were conducted. The results show that the hardness of the composite coatings decreases with the increase of WS2. As the content of WS2 increases, the coefficients of friction (CoFs) of coatings decreases under dry sliding wear. The S2 coating filled with 7.5 wt% WS2 exhibits the lowest wear rate and the best wear resistance under low temperature and dry sliding wear. The coatings form a lubricating film on the worn surface under dry sliding wear at −70°C, improving the wear resistance of the coatings. The primary wear mechanisms are adhesive wear and fatigue wear. The wear rates of the coatings increase with the increasing content of WS2 under low‐temperature grease lubrication. The S1 coating filled with 5.0 wt% WS2 exhibits the lowest wear. The S1 coating demonstrates a CoF of 0.07 and a wear rate of 6.5 × 10−6 mm3N−1 m−1 at 0°C, showing excellent friction‐reducing and wear‐resistant properties. The primary wear mechanism is adhesive wear. The wear mechanisms of polymer coatings are closely related to temperature. The dominant wear mechanisms transfer from abrasive wear to adhesive wear and fatigue wear under dry sliding wear and decreasing temperature. The wear mechanisms transfer from predominantly adhesive and abrasive wear to adhesive wear, fatigue wear, and abrasive wear under grease lubrication. The hardness of the coatings and the behavior of the polymer at various low temperatures are the primary factors that affect the differing wear mechanisms.