Preparation and tribological properties of WS2 solid lubricating coating with dense structure using HiPIMS

In this study, a dense WS2 coating was deposited via high-power impulse magnetron sputtering (HiPIMS) after solving the glow discharge problem, and it was compared with WS2 coating deposited via radio frequency (RF) sputtering. The latter showed a columnar growth, with a loose and porous microstructure. The columnar crystal growth of the former was inhibited, resulting in a more compact coating structure and a more uniform, flatter and smoother surface. Therefore, the structure and tribological properties of WS2 coating prepared via HiPIMS were investigated under different loads and frictional frequencies. Under low loads (up to 15 N), the coefficient of friction (COF) decreased with polishing wear mechanism. Under a high load of 20 N, the COF rapidly increased, the wear rate was the highest, and the wear mechanism changed from polishing to abrasive wear. At low frequencies (5 and 10 Hz), the coating had a low and stable COF, good wear resistance and the wear mechanism was abrasive wear. At high frequencies (≥15 Hz), the COF and wear rates rapidly increased and the wear mechanism changed from abrasive to adhesive wear and plastic fracture. However, the friction and wear rates were similar across different wear mechanisms.