高温合金表面激光熔敷热障涂层组织结构与氧化性能

Structure and Oxidation Properties of Thermal Barrier Coatings by Laser Cladding on Superalloy Substrates

采用 5KW连续CO2 激光器对Ni基高温合金上二次重熔NiCoCrAlY和ZrO2 陶瓷层进行了研究。结果表明 :激光快速熔化和凝固获得定向外延生长、紧密堆积的柱状晶氧化锆陶瓷层。NiCoCrAlY结合层与柱状晶之间存在氧化铝层 ,保证了柱状晶与NiCoCrAlY层的联结。扫描电镜和电子探针联合分析发现 ,氧化锆层与NiCoCrAlY结合层、结合层与基体间均为冶金结合。采用化学改性氧化锆消除了涂层裂纹。高温氧化性能测试得出激光重熔试样氧化动力学近似地遵守抛物线速率方程。在 12 0 0℃ ,空气下激光熔敷TBCs 抗氧化性明显高于等离子喷涂TBCs。

A new type of thermal barrier coating is being developed for gas turbine blades by laser cladding on superalloy substrates.The results show that during rapid melting and and solidification in laser processing,an oriented epitaxial growth,colsely packed columnar structure could be obtained by controlling the process parameters.A alumina layer which exists between the NiCoCrAlY layer and columnar ceramic layer provides for the adherence of the columnar layer to the NiCoCrAlY layer.Scanning electron microscopy and electron probe microanalysis reveal good metallurgical bond between ZrO-2 layer and NiCoCrAlY alloying layer,and between alloying layer and substrate.Chemical modification of ZrO-2 was adopted and eliminated microcrackings of the coatings.High temperature oxidation test reveals oxidation kinetics approximately follow a parabolic rate equation.The oxidation resistance of the laser cladding thermal barrier coatings in air at 1200℃ was significantlky higher than that of plasma sprayed coatings.