I. Gorlach, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
Traditionally thermal spraying of WC-Co is done with HVOF. Although, in the past, there were attempts to use HVAF for spraying of WC-Co, they were unsuccessful. The main advantage of HVOF is high particles velocities, which result in dense and hard coatings. However, it is also recognised that excessive oxidisation of WC-Co due to high flame temperatures is the biggest drawback of HVOF. Also, high operating costs of HVOF makes this process economically unviable in many industrial applications, where there is a need for wear resistant coatings. On the contrary, HVAF has lower flame temperatures and the process is substantially cheaper because it uses compressed air, and it does not require water for cooling. In this research, a HVAF system for thermal spraying of WC-Co was developed. The resulting coatings were evaluated using optical, scanning electron microscopy (SEM), and Vickers microhardness measurements. The quality of sprayed WC-Co coatings shows that HVAF can be an alternative of HVOF with substantial savings on operating costs.
Summary: This paper describes the application of the HVAF process for thermal spraying of WC-Co coatings. The developed HVAF system provides high quality coatings at substantially lower costs in comparison with the traditional HVOF method.
