This paper aims to investigate the effect of coating microstructure, mechanical and oxidation property on the tribological behaviour of low-pressure plasma spraying (LPPS) tungsten carbide/cobalt (WC-Co) coatings.
WC-12Co and WC-17Co coatings were deposited via the LPPS spraying method. Tribological tests on the coatings were performed using a high-temperature ball-on-disc tribometer at temperatures from room temperature (RT, approximately 25 °C) up to 800 °C in ambient air.
WC-12Co coating contained brittle phases, pores and microcracks, which led to the low hardness, and finally promoted the splat delamination and the carbide debonding during wear. WC-17Co coating had higher cobalt content which benefited the coating to contain more WC particles, less brittle phases, pores and nearly no microcracks, and resulted in the high hardness and better wear resistance. Higher cobalt content also decelerated the oxidation rate of the coating and promoted the formation of cobalt oxides and CoWO4, which were able to maintain the load-bearing capacity and improve the tribological behaviour of the coating below 650°C. Above 650°C, the increase of oxidation degree and the decrease of mechanical property deteriorated the wear resistance of coatings.
The LPPS WC-Co coating with higher cobalt content had better tribological properties at different temperatures. The LPPS WC-Co coatings should not be used as wear-resistant coatings above 650 °C.
The authors thank the Natural Science Foundation of Jiangsu Province, China (Grant no. BK20160353), the Natural Science Foundation of Jiangsu Higher Education Institutions of China (Grant no. 16KJB460032), Jiangsu Overseas Visiting Scholar Program for University Prominent Young & Middle-aged Teachers and Presidents, the Research Foundation of SIIT (Grant no. 2017kyqd015) and the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (TAPP) (Grant no. PPZY2015B186) for the financial support. The authors also thank Professor Shu Li, Professor Deli Duan and Associate Professor Yang Liu at the Institute of Metal Research, Chinese Academy of Sciences for the help of the tribological testing.
Geng, Z., Huang, H., Lu, B., Wu, S. and Shi, G. (2019), "Tribological behaviour of low-pressure plasma sprayed WC-Co coatings at elevated temperatures", Industrial Lubrication and Tribology, Vol. 71 No. 2, pp. 258-266. https://doi.org/10.1108/ILT-05-2018-0194Download as .RIS
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