| By reason of variety of microstructure of gradient coating in specific direction, mechanic property and texture change progressively according to thickness, which eliminates interface of thermal stress between metal substrate and ceramic, assuages thermal stress and advances heat-resisting property of coating.Gradient coating adopts oxidative process, A^Oa powder forming surface ceramic coating, Ni/Al+Al as bonding coating. After spraying, specimens conduct oxidation treatment that modifies structure of coating and acquires A^C^ gradient coating in whole form bonding coating to ceramic coating.Subject to oxidation mechanism, in the bonding coating of oxidized specimens, oxides form in the boundary of grain of alloy element and encircle grain, which acts as prohibiting corrosive medium from eroding bonding coating and substrate.Thesis include two parts: heat-resisting property of coating that is tested by heat-shock experiment and corrosion-resisting property of coating that is tested with corrosion weight loss method. Conclusions is as follows:1. Optimal technology of heat-resisting gradient coating: composition of bonding coating being 95%Ni/Al+5%Al or 85%Ni/Al+15%Al, thickness of bonding coating being 0.25mm, thickness of ceramic coating being 0.15mm, oxidized for 5 hours heat insulation at 900 癈 after spraying. Optimal technology of corrosion-resisting gradient coating: composition of bonding coating being 95%Ni/Al+5%Al. thickness of bonding coating being 0.35mm, thickness of ceramic coating being 0.35mm. oxidized for 3 hours heat insulation at 700癈 after spraying.2. Oxidation temperature is the most important factors that influenced heat-shock property of coating.3. Breaking locations of heat-shock lie in where the bonding strength is lowest. Breaking locations of heat-shock specimens that are not oxidized are located in the interface of bonding coating and ceramic coating.According to oxidation temperature, breaking locations of heat-shock specimens that are oxidized are different where they are situated in the AhO3 ceramic coating at 700癈 and 800 癈, stand in the interface of bonding coating and ceramic coating at 1000癈, sit in the bonding coating or the interface of bonding coating and ceramic coating at 900 "C.4. Pore rate of coating of oxidized specimens is greater than not oxidized specimens. Due to stress of interior coating is released, oxidized specimens' heat-resisting property is improved. Corrosion-resisting property of oxidized coating is contrary to variation of pet-pore rate. Thebigger pet-pore rate is, the shorter the time of corrosive inactivation is.5. The corrosive type of oxidized specimens in the 5% boiling HC1 solution is air-pore corrosion.6. Diffusion of oxygen in the bonding coating and substrate is mainly grain-boundary diffusion. Grain-boundary diffusion coefficient is far greater than intragrain diffusion.
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