, Volume 22, Issue 2-3, pp 263-271
Date: 14 Nov 2012

Deposition of WC-Co Coatings by a Novel High Pressure HVOF

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Abstract

WC-Co coatings are primarily deposited using the high velocity oxy-fuel (HVOF) spray process. However, the decomposition and decarburization of carbides during spraying affects the wear performance and fracture toughness of the coatings. In this paper, a novel high pressure HVOF was developed to achieve lower particle temperature and higher particle velocity. It enables combustion chamber pressures up to 3.0 MPa. The influence of combustion chamber pressure and oxygen/fuel ratio on WC-Co particle velocity and temperature levels were analyzed by numerical simulation. The experimental results show that the combustion chamber pressure and the oxygen/fuel ratio have a significant influence on particle velocity and melting degree, as well as on the microstructure and microhardness of the coating. High velocity WC-Co particles in different states, i.e., molten, semi-molten, and non-molten can be readily obtained by changing the spraying conditions. A comparison to the conventional JP-5000 was also performed.

This article is an invited paper selected from presentations at the 2012 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray 2012: Proceedings of the International Thermal Spray Conference, Air, Land, Water, and the Human Body: Thermal Spray Science and Applications, Houston, Texas, USA, May 21-24, 2012, Basil R. Marple, Arvind Agarwal, Laura Filofteia-Toma, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and André McDonald, Ed., ASM International, Materials Park, OH, 2012.