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Influence of Impulse Frequency on Anti-oxidation Property of C-AlPO_4 Coating Prepared by Pulsed arc Discharge Deposition

A C-AlPO4 anti-oxidation coating was prepared on SiC pre-coated C/C composites by pulsed arc discharge deposition.The phase compositions,microstructures and anti-oxidation properties of the as-prepared coatings were characterized by X-ray diffraction,scanning electron microscopy and isothermal oxidation test.The influence of impulse frequency on the microstructure was investigated.Results show that the dense and homogeneous C-AlPO4 coating was achieved when the impulse frequency reaches 1 000 Hz.The as-prepared coatings exhibit excellent anti-oxidation property,which could effectively protect C/C composites from oxidation at 1 773 K in air for 120 h with a mass loss of 0.5%.The anti-oxidation capability decrease of the coating at 1 773 K is due to the generation of cross-holes in the coating,which leads to the failure of self-curing by the metaphosphate glass layer after long time of oxidation.