Deposition of B, C, N coatings on WC–Co substrates—Analytical problems indicating c-BN formation

Abstract

BCN-layers were deposited in a cold-wall reactor by decomposition of Tris(dimethylamino)borane on inductively heated hardmetal (WC–Co) substrates. The substrate temperature was varied between 800 and 1200 °C. XRD measurements of the deposited layers showed weak peaks, that might be explained by crystalline BN-phases, beside strong peaks of the substrate phases WC and Co. Indications for the deposition of the BN-phases could also be found in IR spectra. For an explicit BN phase identification thicker layers were deposited by changing certain deposition parameters, which should provide higher intensities of the XRD-peaks of the BN phases. However, with increasing layer thickness, the BN related peaks decreased, which indicates that the phase causing the XRD peak is located near the substrate/coating interface. Through investigations of substrate reactions the eta-phase (Co 6W 6C) was observed which showed XRD peaks similar to c-BN and h-BN. It could be proved, that the eta-phase is responsible for the XRD peaks but an explanation for the detected IR peaks of the BN phases could not yet be found.