The Effect of Atmosphere on Wear Behaviors of HVOF Sprayed WC-Co Coatings at Elevated Temperatures

Wear behaviors of HVOF sprayed WC-12Co and WC-17Co coatings at temperatures from room temperature (RT,~25 ℃) up to 650 ℃ in air and in argon were studied by a ball-on-disc tribometer. The wear track morphologies,compositions and oxide phases after rubbing tests were investigated by scanning electron microscopy,energy dispersive X-ray spectrometer and Raman spectroscopy. The synergistic effect of oxidation and wear of coatings was investigated. The results show that oxygen played an important role during wear of WC-Co coatings. In air,the oxides on the wear tracks reduced wear at RT ~ 550 ℃,which means that the oxidation inhibited wear. At 650 ℃,the vigorous oxidation degraded the coating properties and resulted in the severe wear,which means that the oxidation aggravated wear. In argon,the wear of coatings was severe at RT ~ 550 ℃ and was significantly higher than that in air. The wear decreased as the temperature elevated due to mild oxidization. At 650 ℃,the wear of the coating was even lower than that in air,which is attributed to the inhibition of vigorous oxidation. As a result,WC-Co coatings should not be used as wear-resistant coatings in the oxygen-deficient environment whether at RT or at elevated temperatures.