Effects of pulse power and argon flux flow rate on mechanical and tribological properties of diamond-like carbon coatings prepared using high power impulse magnetron sputtering technology

Abstract

Diamond-like carbon (DLC) coatings were deposited on SKH51 disks using a high power impulse magnetron sputtering (HiPIMS) system. Preliminary experiments were performed to determine the HiPIMS conditions which maximized the DLC coating hardness. The composition, structure, mechanical and tribological properties of the DLC coatings were then systematically explored for different values of the HiPIMS pulse power and argon flux flow rate. For given values of the HiPIMS deposition time, pulse current and deposition distance, a high DLC coating nanohardness (19.77 GPa) was obtained using a pulse power of 5 kW and an argon flux flow rate of 100 sccm. However, the coating exhibited the lowest adhesive strength (i.e., a critical load (Lc) of just 6 N). By contrast, the coating prepared with a pulse power of 5 kW and an argon flux flow rate of 80 sccm had the highest nanohardness (22.88 GPa) and a greatly improved adhesive performance (Lc = 73 N). However, it showed the lowest wear rate among all of the coatings when sliding against an Al2O3 ball under loads of 6–14 N. The coating deposited with a pulse power of 4 kW and an argon flux flow rate of 100 sccm possessed the highest critical load of all the coatings (Lc = 94 N), and thus exhibited the longest wear life when sliding against the Al2O3 ball (∼129,756 cycles). When sliding against an AISI 52100 ball, all of the coatings showed an excellent tribological performance, including a low wear rate and a long wear life (more than 150,000 cycles).