CVD of Alternated MCD and NCD Films on Cemented Carbide Inserts

摘要

Chemical vapor deposition (CVD) diamond coating of cemented carbide cutting tools has been an alternative to increase tool-life. Experiments have shown that residual stresses produced during films growth on cemented carbide inserts significantly increases with increasing film thickness of up to 20 μm and usually leads to film delamination. In this work alternated micro- and nanocrystalline CVD diamond films have been used to relax interface stresses and to increase diamond coatings performance. Cemented carbide inserts have been submitted to a boronizing thermal diffusion treatment prior to CVD diamond films growth. After reactive heat treatment samples were submitted to subsequently chemical etching in acid and alkaline solution. The diamond films deposition was performed using hot-filament chemical vapor deposition (HFCVD) reactor with different gas concentrations for microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films growth. As a result, we present the improvement of diamond films adherence on cemented carbide inserts, evaluated by indentation and machining tests. Samples were characterized by scanning electron microscopy and energy dispersive X ray for qualitative analysis of diamond films. X-ray diffraction was used for phases identification after boronizing process. Diamond film compressive residual stresses were analyzed by Raman scattering spectroscopy.