Recent Advances in the Deposition of Diamond Coatings on Co-Cemented Tungsten Carbides

R Polini,G Rubino,M Barletta,S Vesco

doi:10.1155/2012/151629

Abstract

Co-cemented tungsten carbides, namely, hard metals are largely used to manufacture high wear resistant components in several manufacturing segments. Coating hard metals with superhard materials like diamond is of utmost interest as it can further extend their useful lifespan. The deposition of diamond coatings onto WC-Co can be extremely complicated as a result of poor adhesion. This can be essentially ascribed to (i) the mismatch in thermal expansion coefficients between diamond and WC-Co, at the typical high temperatures inside the chemical vapour deposition (CVD) chamber, generates large residual stresses at the interface; (ii) the role of surface Co inside the WC-Co matrix during diamond CVD, which promotes carbon dissolution and diffusion. The present investigation reviews the techniques by which Co-cemented tungsten carbides can be treated to make them prone to receive diamond coatings by CVD. Further, it proposes interesting ecofriendly and sustainable alternatives to further improve the diamond deposition process as well as the overall performance of the coated hard metals.

Highlights

Co-(5.8% wt.) cemented tungsten carbides belong to the class of hard metals, widely used for the manufacturing of cutting tools, sliding bearings, drawing dies, and a large variety of wear-resistant components
High temperature chemical vapor deposition (CVD) of diamond coatings onto Co-cemented tungsten carbide (WC-Co 5.8% wt.) is a highly effective procedure to further increase the useful lifespan of hardmetal components by application on them of a superhard and chemically inert thin layer
(2) The interlayer surface morphology played an important role in determining the performance of thin diamond films

Summary

Introduction

Co-(5.8% wt.) cemented tungsten carbides belong to the class of hard metals, widely used for the manufacturing of cutting tools, sliding bearings, drawing dies, and a large variety of wear-resistant components. High temperature chemical vapor deposition (CVD) of diamond coatings onto Co-cemented tungsten carbide (WC-Co 5.8% wt.) is a highly effective procedure to further increase the useful lifespan of hardmetal components by application on them of a superhard and chemically inert thin layer. The diamond deposition process is affected by several drawbacks These are essentially ascribable to the onset of large residual stresses in the coating due to the mismatch in the thermal expansion coefficients between diamond and WC-Co and to the presence of the Co-based binder. The interlayers are deposited on the WCCo substrate and act as C and Co diffusion barrier during the CVD process They interpose themselves between the WC-Co and diamond reducing the mismatch in their thermal properties [5].

Methods

Results

Conclusion