Comparative evaluation on friction and wear characteristics of SiC, Si(3)N(4), Al(2)O(3), and ZrO(2) sliding against PEEK composite for seawater hydraulic axial piston pumps

Comparative investigation on friction and wear properties of SiC, Si(3)N(4), Al(2)O(3), and ZrO(2) lubricated with seawater was carried out on a ring-on-ring contacted tribological test apparatus, and their worn surfaces were observed by an ultra-depth optical microscope. The results reveal that the friction coefficients of Si(3)N(4) and SiC are obviously lower than those of Al(2)O(3) and ZrO(2) when they slide against the polyetheretherketone (PEEK) composite in seawater, and the friction stability of ZrO(2) is so poor that it is not suitable for seawater hydraulic piston pumps. When the contacted load increases from 400 to 1000 N, the wear rate of Al(2)O(3) is still the highest, while the wear rates of SiC and Si(3)N(4) change from positive to negative, which indicates that plastic transfer is occurred under a heavier load. When they slide against the PEEK in seawater, the main tribological mechanism of SiC, Si(3)N(4), and Al(2)O(3) is slightly abrasive wear, while both abrasive wear and adhesive wear occur for ZrO(2). Generally, both SiC and Si(3)N(4) have wide prospect applied in seawater hydraulic piston pumps, and particularly Si(3)N(4) exhibits excellent friction and wear properties in seawater