Thermally induced defects in a polycrystalline diamond layer on a tungsten carbide substrate

Characterisation of thermally degraded polycrystalline diamond

“…This results in the presence of tungsten and carbon in solid solution with cobalt. Tungsten atoms will fit substitutionally in the cobalt (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) wt.% at 1250°C) and carbon atoms will fit interstitially in the cobalt (0-0.2 wt.% at elevated temperatures). The solid solution elements are expected to increase the lattice parameter of the cobalt [26].…”

“…Pin-on-disc experiments performed at high temperatures showed that cracking of the PCD microstructure only occurred at temperatures above 700°C, where graphitisation of the material could be a contributing factor [9]. To a lesser degree, other factors considered in the study of thermal degradation of PCD are oxidation of the diamond [13], oxidation of the cobalt [14,15], the macro-residual stress state between the diamond layer and the tungsten carbide backing [16], and chemical reactions between the rock/cooling fluids used during operations [17].…”

Microstructures and thermal damage mechanisms of sintered polycrystalline diamond compact annealing under ambient air and vacuum conditions

“…After annealing at 500°C in ambient air, the oxidization reaction of W and Co has occurred with the change of the color of WC-Co substrate (Fig. 5b), which has been mentioned in previous reference [17]. However, Fig.…”

“…2c. The previous references [8,17] have indicated that W, with very low quantity, comes from thermal diffusion and infiltration during sintering process.…”

“…With the disappearance of diamond and increasing of Co 3 O 4 , ball-like bugles and micro-holes eventually appeared. Recently, Masina et al [17] heated PDCs by laser in ambient air to explore the thermally induced defects. It presented that the diffusion of Co and W resulted in the formation of Co x O y and W x O y on PDC surface, but no graphitization of diamond was found.…”