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

Tribological properties of Ni3Al-Cr7C3 coatings without and with 0.2 wt.% b oron doping at room temperature under dry sliding were measured by using a ball-on-disc reciprocating tribotester for investigating effect of boron do ping on the tribological properties. Microhardness of the coatings was meas ured. The worn surfaces of the coatings were examined by scanning electron microscopy (SEM). The results showed that hardness of the coatings was decr eased with boron doping. Wear of the coatings decreased a lot at intermedia te 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. S ensitivity of coatings wear to load and sliding speed at intermediate slidi ng speed had a significant decrease with boron doping. Friction of the coat ings 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 f rom brittle fracture to surface cracking with boron doping. (C) 2001 Elsevi er Science B.V. All rights reserved.