CoCrNiAlY涂层制备工艺对组织形态及高温氧化行为的影响

Effects of Processing Technique on Microstructure and High Temperature Oxidation Behavior of CoCrNiAlY Coating

为了研究CoCrNiAlY涂层微观组织结构对高温氧化行为和剥落行为的影响规律,采用激光熔覆技术和等离子喷涂工艺在718高温合金表面制备CoCrNiAlY涂层,观察其微观组织形态。利用XRD和SEM对1150℃高温氧化试验样品进行氧化层物相分析和形貌观察。结果表明,激光熔覆制备的CoCrNiAlY涂层中形成了胞状亚结构的等轴晶凝固组织,相对于等离子喷涂制备的CoCrNiAlY涂层结构更致密,具有更优异的抗高温氧化性能。在高温氧化过程中,等离子喷涂CoCrNiAlY涂层生成了以Cr_2O_3结构为主的复合氧化膜。激光熔覆CoCrNiAlY涂层生成Al_2O_3结构的单一氧化膜,而且熔覆层中原位形成的Y_2O_3钉扎作用能有效提高氧化膜的抗剥落性。文中系统分析讨论了两种不同工艺制备的组织形态对高温氧化膜形成机制的影响,激光熔覆涂层在高温下主要是以界面扩散方式形成致密的Al_2O_3膜,等离子喷涂涂层在高温下以界面反应的方式快速形成Cr_2O_3复合氧化膜。

CoCrNiAlY coatings on the 718 superalloy surface were produced by laser melting depositing technique and air plasma spraying process. The microstructure was observed to study the effect of microstructure on high temperature oxidation behavior and spallation behavior of the CoCrNiAlY coating. Phase and oxide layer morphology exposed to high temperature oxidation at 1150 °C were analyzed by XRD and SEM. Results show that the surface of the CoCrNiAlY coating prepared by laser melting deposition is denser and exhibits more excellent resistance to high temperature oxidation than that of the air plasma spraying CoCrNiAlY coating. During the high temperature oxidation, the air plasma spraying CoCrNiAlY coating produces an oxide layer containing Cr2O3 as a main component, and the laser melting deposited CoCrNiAlY coating forms the oxide layer with Al2O3 as the main component shows good spalling resistance. In-situ Y2O3 particles formed in the CoCrNiAlY coating during laser melting deposition are thought to be beneficial for anchoring the oxide layer. The effects of processing technique of the CoCrNiAlY coating on microstructure formation and high temperature oxidation mechanism were analyzed. Oxidation of the laser melting deposited CoCrNiAlY coating yields a dense Al2O3 layer through interfacial diffusion,while oxidation of the air plasma spraying coating results in a composite Cr2O3 layer through interface reaction.