N. Petsas, G. Papapanos, M. Vardavoulias, PyroGenesis S.A., Lavrio, Greece; J. P. Celis, Katholieke Universiteit Leuven, Leuven, Belgium; P. Matteazzi, CSGI, Vascon di Carbonera (TV), Italy; A. Moutsatsou, National Technical University of Athens, Athens, Greece
The purpose of the present study is to investigate the influence of critical HVOF spray parameters on mechanical properties of WC–12Co coatings, using nanophased powder as feedstock material. For this reason, the Taguchi design of experiments method was used for the development and optimization of process parameters and coating properties. An L9 table was used for the evaluation of the effect of spray distance, oxygen/fuel ratio, gun traverse speed and feed rate on coating microhardness, adhesion strength, porosity and deposition efficiency – thickness. Results show clearly that each parameter affects in a different way and percentage each property. Furthermore, the comparison of XRD diagrams with a respective conventional coating indicates that the nanostructure of the initial powder is maintained in the coating, whereas in the conventional one the formation of W2C phase is evident. Finally, fretting tests show similar behavior in terms of friction coefficient, but a significant improvement regarding wear resistance in the case of the nanophased coating.
Summary: The present study deals with the influence (qualitative and quantitative) of HVOF spray parameters on the properties (microhardness, adhesion strength, porosity, deposition efficiency) of nanophased WC-12Co coatings. The nanostructure is maintained, without the formation of W2C. The tribological behavior is improved compared to a respective conventional coating.
