Improved CVD diamond coatings on WC-Co tool substrates

Tungsten carbide tools with different cobalt concentrations (3 and 6%) have been treated with different surface cleaning procedures for deposition of diamond and multilayer diamond composite films. Cleaning with organic solvents, surface etching to remove cobalt from the surface, and hydrogen plasma etching to decarburize WC and etch remove cobalt have been used in combination to improve the adhesion of diamond films deposited on the tool substrates. Diamond layers are deposited by microwave plasma chemical vapor deposition (MPCVD) after introducing surface nucleation by suspension with sub-micron size diamond crystallites. TiN and TiC films are deposited as intermediate layers that prevent diffusion of cobalt or as embedding layers that also anchor diamond crystallites to the tool substrate. A continuous top layer of diamond was deposited for different periods of time (15-36 h) to obtain diamond film thickness ranging from 15 to 36 mum. The performance of diamond-coated tools has been tested by machining particleboard. The tool surfaces were characterized using measurements of wear of the cutting edge. Microstructural characterization using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of the composite layers on the tool surfaces is performed. The quantitative evaluation of wear and microstructural characterization were used to determine the mechanisms of wear of the cutting edge. The results are used to conclude the diamond tool coating procedure that provides the best performance in machining particleboard. (C) 2002 Elsevier Science B.V. All rights reserved.