Deposition of Ti(C, N)-TiB_2 Composite Coating by Reactive LPPS

Ti(C, N)-TiB2 composite coatings were deposited by means of reactive low pressure plasma spraying (LPPS) based on the technology of self-propagating high-temperature synthesis (SHS). The original powders were mixtures of Ti and B4C powders. The powders were mixed by ball mill and then spray-dried and at last sintered to be suitable for spraying. Two spraying distances were selected for LPPS. Scanning electron microscopy (SEM) was used to investigate the morphologies of powders for spraying and the microstructures of the coatings. The phase compositions of coatings were measured by X-ray diffraction (XRD). Spray-dried and sintered powders are denser and better bond than only spray-dried powders. The composite coating is composed of TiB2, TiC0.3N0.7, TiN0.3, Ti4N3-x and impurity phase of Ti5Si3 with 300 mm spraying distance. Partly unreacted B4C powders remained in the coating for 240 mm spraying distance, which may be inadequate reaction. No titanium oxide was detected in the composite coating for the relative high vacuum degree of LPPS. The anti-corrosion property of LPPS sprayed Ti(C, N)-TiB2 composite coating with 300 mm spraying distance in electrolytic solution is superior to that of 240 mm spraying distance. Microhardness of Ti(C, N)-TiB2 composite coating is relatively low due to the unconsolidated structure of the coating. The solving methods to improve property of composite coating are finally put forward in the paper.