Effect of hydrostatic pressure on the tribological behavior and mechanism of the multilayered graphite like-carbon (GLC) coating

In this study, the tribological behavior and mechanism of multilayered graphite-like carbon (GLC) coatings under different hydrostatic pressures (0.1–60 MPa) were investigated via a simulated deep-sea friction and wear test system. The morphology and composition of the friction interface were thoroughly characterized. The findings revealed that the coefficient of friction (COF) was greater (but did not surpass 0.02) under conditions of elevated hydrostatic pressure or heavy load. The GLC coating mainly experiences abrasive wear, and the degree of wear intensifies with increasing hydrostatic pressure and load. The graphitization of the friction interface and the production of silicon-based lubrication products are becoming increasingly evident. Consequently, the effect of hydrostatic pressure on the frictional performance of GLC coatings is achieved by changing the state of the frictional contact surfaces. Essentially, hydrostatic pressure modifies the real contact area of the friction pair by generating additional compressive loads such that an increase in hydrostatic pressure has a similar effect on an increase in the applied load. As the hydrostatic pressure and applied load increase, the trend of abrasion smoothing on the surfaces of the friction pair becomes more pronounced. The graphite transfer film and silicon-based material generated during the friction process improve the lubrication performance of the friction pair, resulting in extremely low wear of the friction pair.