Tribological properties of Ni3Al-Cr7C3 composite coating under water lubrication

The tribological properties of Ni3Al-Cr7C3 composite coating under water lu brication were examined by using a ball-on-disc reciprocating tribotester. The effects of load and sliding speed on wear rate of the coating were inve stigated. The worn surface of the coating was analyzed using electron probe microscopy analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show the friction coefficient of the coating is decreased under wa ter lubrication. The wear rate of the coating linearly increases with the l oad. At high sliding speed, the wear rate of the coating is dramatically in creased and a large amount of the counterpart material is transferred to th e coating worn surface. The low friction of the coating under water lubrica tion is due to the oxidizing of the worn surface in the wear. The wear mech anism of the coating is plastic deformation at low normal load and sliding speed. However, the wear mechanism transforms to microfracture and microplo ughing at high load with low sliding speed, and oxidation wear at high slid ing speed. It is concluded that the contribution of the sliding speed to an increase in the coating wear is larger than that of the normal load. (C) 2 000 Published by Elsevier Science Ltd.