Effects of boron doping on tribological properties of Ni₃Al-Cr₇C₃ coatings under dry sliding

Tribological properties of Ni₃Al-Cr₇C₃ coatings without and with 0.2 wt.% boron doping at room temperature under dry sliding were measured by using a ball-on-disc reciprocating tribotester for investigating effect of boron doping on the tribological properties. Microhardness of the coatings was measured. The worn surfaces of the coatings were examined by scanning electron microscopy (SEM). The results showed that hardness of the coatings was decreased with boron doping. Wear of the coatings decreased a lot at intermediate sliding speed with boron doping. But the wear increased a little at low sliding speed and did not change at high sliding speed with boron doping. Sensitivity of coatings wear to load and sliding speed at intermediate sliding speed had a significant decrease with boron doping. Friction of the coatings at low sliding speed was increased but that at high sliding speed was not changed with boron doping. Wear mechanism of the coatings was changed from brittle fracture to surface cracking with boron doping.