A boron-doped diamond like carbon coating with high hardness and low friction coefficient.

In this study, boron carbide (B 4 C) was reactively sputtered with acetylene to form a boron containing diamond-like carbon (DLC) coating. The flow rate of acetylene significantly affects the composition and thus the mechanical behavior of the coating. When optimal acetylene flow rate was used (10 sccm in this study), the coating has a B/C ratio of ~1% and possesses the high hardness of B 4 C and the low friction of DLC in addition to good adhesion with the 52100 steel substrate. It was found that the new coating consisted of nanocrystalline boron carbide precipitates homogeneously distributed in an amorphous hydrocarbon matrix forming a boron-doped a-C:H film. The new coating exhibited wear resistance superior to a commercial W-doped DLC coating currently used on rolling element bearings and gears. The best wear resistance and lowest friction coefficients were obtained in coatings with a B/C ratio of ~1%. • Boron carbide was reactively sputtered with acetylene to form a boron containing diamond-like carbon (DLC) coating. • Boron carbide precipitates homogeneously distribute in an amorphous hydrocarbon matrix forming a boron-doped a-C:H film. • The new coating combines the high hardness of boron carbide and the low friction of DLC. • Its wear resistance is superior to a commercial W-doped DLC coating currently used on rolling element bearings and gears. [ABSTRACT FROM AUTHOR]