Tribological Properties of Friction Pair between 316L Stainless Steel and CF/PEEK with Nonsmooth Surface under Seawater Lubrication

Abstract

This work improves the tribological behavior via innovative surface designs for slipper pairs in seawater axial piston pumps. 316L stainless steel and carbon fiber/polyether ether ketone (CF/PEEK) were selected as friction pair matching materials due to their good corrosion resistance, self-lubrication, and wear resistance. One type of smooth surface and five different types of pit nonsmooth surfaces were created on CF/PEEK specimens. Rotational sliding tests were performed on a friction and wear tester at a load of 200 N at five different sliding speeds (0.79, 1.18, 1.57, 1.96, and 2.36 m/s) under seawater lubrication. The experimental results indicate that the friction process of the smooth surface friction pair is mainly based on abrasive wear and adhesive wear. The friction coefficient range is 0.05–0.08, the specimen contact temperature is 38–75 °C, and the wear rates of 316L and CF/PEEK are 2.3 × 10−5 to 1.2 × 10−4 mm3/(MPa·m) and 5.6 × 10−4 to 7.6 × 10−3 mm3/(MPa·m), respectively. Pits on the specimen surface produce a hydrodynamic effect and store wear debris. The friction process of the nonsmooth surface friction pair is mainly controlled by a ploughing mechanism with only a slight amount of adhesive wear. The friction coefficient range is decreased to 0.03–0.07, the specimen contact temperature is decreased to 28–54 °C, and the wear rates of 316L and CF/PEEK are decreased to 1.2 × 10−5 to 9.1 × 10−5 mm3/(MPa·m) and 2.6 × 10−3 to 7.1 × 10−3 mm3/(MPa·m), respectively. The geometrical arrangement of the elliptical and tri-prism pits increases the convergence gap range and produces a higher bearing capacity. As the sliding speed increases, the friction coefficient first decreases and subsequently slightly increases, the specimen contact temperature increases, and the wear rate decreases.