Effects of SiC on Microstructure and Properties of Coatings Prepared by Plasma Spraying Cr2O3-Al-SiC Powder

Four kinds of chromium carbide composite coatings were successfully prepared on the surface of TC4 titanium alloy by plasma spraying Cr2O3-Al-SiC composite powder. The effects of SiC content in composite powder on the microstructure and properties of the as-prepared coatings were investigated. The results showed that the desired phases of Cr7C3, CrSi2 and Al2O3 were synthesized in situ through the reactions among Cr2O3, Al and SiC powders. However, due to the different content of each phase in coatings, the microstructure and properties were different. When the SiC content increased from 5 to 12 wt.%, the porosity of the coatings decreased, and the microhardness and toughness increased. Continue to increase SiC content to 19 and 30 wt.%, the porosity of the coatings increased, and the microhardness and toughness decreased. When the SiC content was 12 wt.%, the as-prepared coating had the lowest porosity (3.20%), the highest microhardness (1262.2 HV0.1) and the best fracture toughness (3.3 MPa m(1/2)) due to the higher reaction degree and better melting state of the composite powders in the plasma jet.