The Investigation On Antioxidant Of In-situ Synthesis High Tempertature Composite Coatings On Graphite Electrode Surface By Argon Arc Cladding

In this paper, the antioxidant composite coatings of C-Si, C-Si-Ti and C-Si-Zrwere prepared on the graphite electrode surface from the raw materials of Si, Ti andZr power by using the argon arc cladding technology. The microstructure and thephase composition of composite coating were analyzed by using scanning electronmicroscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction（XRD）. Under optimum process, coatings showed the appearance of smooth, metallicsheen, a good combination between the composite coating and the graphite matrix, noobvious defects. At the temperature conditions both1100℃and1300℃, thecomposite coating antioxidant properties both C-Si-Ti system and C-Si-Zr systemwere tested, and the two kinds of coating oxidation mechanism were analyzed.The test results showed that: the C-Si composite coating is prepared with Sipower as the raw material, whose main phases are Si and SiC. The cladding layer iscombined closely with the matrix, and the bond zone has no obvious defects. C-Si-Ticomposite coating is prepared on the surface of the C-Si transtion coating, which iscomposed of Ti₅Si₃、TiSi₂and TiSi. At1100℃and10h, C-Si-Ti composite coatingproduced self-healing oxide film of SiO₂-TiO₂, which could be closed by the presenceof pores and cracks in the coating, so that the oxidation film was dense uniform andblocked the diffusion of oxygen to coating inside. But at1300℃and10h, themicrostructure of oxidation film was subjected to severe thermal erosion, and surfaceoxidation film began to appear failure, leading to oxidation resistance graduallydecreased. C-Si-Zr composite coating is prepared on the surface of the C-Si transtioncoating, which is composed of ZrSi2_and ZrSi. At1100℃and1300℃for10h, thechange rates of the oxidation quality of C-Si-Zr system composite coating were0.866mg/（mm₂·h） and0.934mg/（mm₂·h）, and the quantity of SiO2-ZrO2slowly increasedin coating internal. It was benefit of improving oxidation resistance, the slow increaseof the oxide volume causing oxidation film stress relaxation.