Influences of WC-Co hard metal substrate pre-treatments with boron and silicon on low pressure diamond deposition

Abstract

Diamond coatings were produced on WC-Co hard metal substrates. To improve the adhesion between the diamond coating and the substrate a substrate surface pre-treatment with boron or with silicon vapor was applied. This surface pre-treatment resulted in an increase in both the diamond nucleation density and the diamond growth rate. Simple adhesion tests confirmed an improved adhesion of thin diamond layers as compared with those on untreated hard metal substrates. Secondary ion mass spectroscopy (SIMS) depth profiles revealed an enrichment of B or of Si at the substrate-diamond interface due to the pre-treatment procedure. The correlation of the Co and W depth profiles in samples coated for 12 and 24 h supports the theory of diamond dissolution into the substrate. Co was detected only in the interface regions and on the surface of the diamond layers but not in the bulk of the thick layers. The SIMS results confirm X-ray examinations of the hard metal Co binder phase.