Growth and characterization of multilayer hot-filament chemical vapor deposition diamond coatings on WC–Co substrates

Abstract

The diamond coating of tungsten carbide (WC)–cobalt (Co) hard metals has been the focus of various research activities mainly due to growing interest in diamond-coated tools for industrial machining of different materials. In this work, multilayered diamond coatings have been grown on pretreated tungsten carbide–cobalt substrates by hot-filament chemical vapor deposition. Two types of multilayer coatings have been prepared: (a) three-layer (alternating nanocrystalline diamond and microcrystalline diamond films) and (b) five-layer (alternating ultrananocrystalline and microcrystalline diamond films). The morphology, roughness, structure, thickness, adhesion of these coatings have been investigated using atomic force microscopy, field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, nanoindentantion and Rockwell C indentation tests at 600 N load. Raman spectra of the two types of samples exhibited sharp characteristic bands of nanocrystalline diamond and a centered peak at 1340 cm−1. The displacement of this peak in relation to the natural diamond peak (1332 cm−1) can be attributed to graphitic inclusions in diamond grain boundaries and the thermal coefficient mismatch of the multilayer coating–substrate system. Roughness surface measurements showed very smooth surfaces for both samples. Although the substrate has a high binder content, the results show that well-adhered chemical vapor deposition diamond multilayer coatings were produced.