LATTICE DISORDER AND TEXTURE IN DIAMOND COATINGS DEPOSITED BY HFCVD ON CO-CEMENTED TUNGSTEN CARBIDE

Diamond coatings were deposited by hot filament chemical vapour deposi tion on 5.8 wt.% Co-cemented tungsten carbide (WC-Co). Under the same deposition conditions, two sets of samples were produced by varying th e CH4 percentage (0.5 and 1.0%) in the H-2 atmosphere, and changing th e substrate temperature in the range 650-950 degrees C. The effect of different CH4 percentage and of temperature on diamond microstructure was investigated by scanning electron microscopy (SEM) and X-ray diffr action (XRD). In particular, pole figure measurement and line profile analysis (LPA) were used to study diamond texture and lattice disorder , respectively. Diamond grains were not preferentially oriented for de position temperatures below 800 degrees C. Above this temperature, a [ 111] fibre texture developed in samples deposited with 0.5% CH4 in H-2 . The XRD profile broadening indicated a marked increase of lattice di sorder in the diamond him with increasing deposition temperature. This observation was correlated with the Raman peak broadening, also attri buted to lattice disorder effects. A detailed LPA showed a decrease of crystallite mean size and a corresponding microstrain increase with r aising temperature, although SEM morphological observations indicated a progressive grain coarsening at higher deposition temperatures.