Mechanical properties of WC coatings evaluated using instrumented indentation technique

Abstract

Instrumented indentation tests have been conducted on the surface and cross-section of the two WC based coatings obtained by means of high velocity oxygen fuel thermal spray techniques in order to investigate their mechanical properties. The yield strength of the coatings has been determined by means of the Zeng and Chiu model. In addition, the absolute hardness of the coatings has been determined by means of the modified proportional specimen resistance model. Additionally, conventional spherical indentation tests were carried out on the surface of the coatings, aimed at determining the yield strength by means of the equations employed in classical elastic contact mechanics. The analysis indicates that the yield strength determined from the Zeng and Chiu model is of 3·5 and 3·1 GPa for the WC–10Co–4Cr and WC–12Co coatings respectively. The absolute hardness of the WC–10Co–4Cr coating was found to be of 11·1 GPa, whereas that of the WC–12Co was of 9·3 GPa.

Keywords:

• WC–Co coatings
• Instrumented indentation tests
• Spherical indentation
• Elastic contact mechanics equations
• Yield strength

Acknowledgements

The present investigation has been carried out with the support of the Scientific and Humanistic Development Council of the Universidad Central de Venezuela (CDCH-UCV) through project nos. PI-08-7823-2009/2 and AIB-08-8539-2012. The authors acknowledge the assistance of G. Cariello for conducting the spherical indentation experiments. Professor Puchi-Cabrera gratefully acknowledges the financial support of the Conseil Régional Nord-Pas de Calais, France, through the International Chair Program 2011.