Study On Preparation Of Resistance To High Temperature Oxidation Coating For C/SiC Composite

C/SiC composite has become key materials of aerospace thermal structural components because of its excellent properties, but carbon fiber is easy to be oxidized, which limits the use of C/SiC composites at high temperature. The paper based on the purpose of the improvement of C/SiC composite oxidation and ablation resistance, fabricated self-healing ZrB2-MoSi2 coating containing borosilicate glass. Studied and analyzed oxidation resistance of the ablative coating as well as coating failure mechanism.In this paper, the compound powder with spherical morphology and appropriate particle size was synthesized by spray-drying, which meets the requirements of plasma spraying. Optimize the parameters of spray-drying: solid content 40%, binder content 0.3%, inlet temperature 250℃, atomizer frequency 50 Hz, rotate speed of pump rotation 30 rpm.Sintering method and Induction Plasma Spheroidization(IPS) were selected respectively to sintering the agglomerated powders in order to improve the density of the compound powder. The better Sintering method parameter was 800℃ for 2h and the better parameter of the power of IPS was 18 Kw. Compared with sintering method, powders treated by IPS had a better performance.After IPS, the mobility and loose density of powders increased by 57.6% and 96.7%.Atmosphere plasma spraying and high-energy plasma spraying were used respectively to prepare anti-oxidation coating. Study on effect of spraying parameters on microstructure of coating. Optimize the main parameters of atmosphere plasma spraying: work current 950 A, main gas flow rate 70 SCFH, and auxiliary gas flow rate 60SCFH; Optimize the main parameters of high-energy plasma spraying work current 480 A, main gas flow rate 230 LPM, auxiliary gas flow rate 85 LPM, and Powder feed rate 3.0rpm. The coating with a dense structure prepared by using the optimized processing had a good bonding with the substrate.The property of anti-oxidation of coated specimen was test by oxy-acetylene flame, when ablation distance is 30 mm, after ablation time 300 s, mass ablation rate was 15.1×10-4g/s; when ablation distance is 20 mm, after ablation time 300 s, mass ablation rate was 19.1×10-4g/s, while uncoated specimen`s mass ablation rate was 45.8×10-4g/s.During the process of ablation, borosilicate glass sealed pores of ZrO2 skeleton, preventing oxygen diffusion, the coating had good oxidation resistance; at higher temperature borosilicate glass evaporated seriously, ZrO2 with loose structure was unable to impede the diffusion of oxygen and the coating failure in anti-oxidant properties.