Reactive plasma sprayed TiC-SiC composite coatings and its thermal stability
Carbides and silicides with strong covalent bonds are important candidate materials for high temperature protective coatings,but it is difficult for single-phase material to achieve good comprehensive properties.In order to improve the high temperature performance of single TiC ceramics,TiC-SiC composite coatings were prepared by reactive plasma spraying technology with raw materials of Ti,SiC and graphite powders.This study features an examination of the phase composition,microstructure and morphology of coatings by SEM and XRD,as well as a comparative analysis of the micro-hardness and the Weibull distribution.The results show that the Ti powder reacts with graphite powder then forms TiC and the as-sprayed coatings main phases are consisted of TiC and SiC.According to the micro-hardness and the Weibull distribution curves of composite coatings,the average micro-hardness(1 070.8HV0.2)of the coating sprayed with Ti-C-5wt.％SiC powders is slightly lower than that of the coating(1 127HV0.2)prepared with Ti-C-20wt.％SiC powders.However,the dispersion coefficient β and correlation coefficient R of the coating sprayed with Ti-C-5wt.％SiC powders are higher than that of the coating fabricated by Ti-C-20wt.％SiC powders and this can be explained by relatively uniform microstructure of the coating fabricated by Ti-C-5wt.％SiC powders.Besides,based on the test results of 900～1 100 ℃ thermal impact and 1 000 ℃ oxidation resistance of coatings,the coating fabricated with Ti-C-5wt.％SiC powders presents better heat impact resistance and oxidation resistance due to its relatively high compactness which can reduce the opportunities and efficiencies of exposure to the oxygen at high temperature.
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