Oxidation Behavior of Bilayered Ceramic Particle-reinforced Enamel Composite Coating on Nickel-based Superalloy K38G at 1000℃
镍基高温合金上双层搪瓷-陶瓷复合涂层1000℃氧化机理

A bilayered enamel-ceramic composite coating,consisted of an inner layer of enamel-50 mass%corundum and an outer layer of enamel-50 mass%quartz,was prepared on nickel-based superalloy K38G by spray-sintering technique.The coating is dense with glaze surface and has good adhesion to the substrate.Its oxidation behavior at 1000°C for 120 h was studied by means of thermogravimetry,SEM,EDS and XRD.Cristobalite,a high-temperature polymorph of quartz, and zircon and albite precipitates were detected in the as-prepared enamel-ceramic composite coating.In addition,Ni,Co and Cr were present in the inner layer of enamel-corundum.The mass gain of the coated alloy after 120 h oxidation was about 0.2 mg/cm~2,quite lower than those of NiCrAlY coatings.Most of the quartz particles in the coating transformed into cristobalite after oxidation tests.Besides,orthoclase was detected too.Ni-enrichment was observed in the outermost region of the outer layer,while Cr-enrichment was found in the inner layer close to the inner/outer interface.And Ni-,Cr-,Al-enrichment were found in the inner layer near the substrate either of the as-prepared samples or of the samples after oxidation tests.