HVOF 制备 MCrAlY 涂层过程中 WC 杂质颗粒的演变遗传行为研究

在热喷涂工业生产过程中,喷涂制备不同材料体系的涂层之前需要对送粉路径(送粉罐、送粉盘、搅拌器、送粉管路、送粉针)进行清理,但由于送粉路径内部结构复杂且存在静电吸附效应,使得残留于喷涂系统的粉末无法被完全去除,通常以微量杂质颗粒的形式被带入新涂层,进而影响新涂层的性能。为此,本文研究了在单晶基材表面采用高速火焰(HVOF)喷涂制备MCrAlY涂层过程中,送粉路径残留的WC杂质颗粒(WC-10Co4Cr)在涂层及涂层与基材界面处的遗传演变行为,分别采用SEM、EDS分析了WC杂质在喷涂态、热处理态涂层中的微观组织和相组成。研究结果表明,WC杂质颗粒确实存在于MCrAlY涂层中,并在后期热处理及氧化试验中进一步分解而固溶于涂层中,甚至扩散至单晶基材内部引起含W碳化物的生成,影响涂层及单晶基材的显微组织,改变局部的成分均匀性。同时,本文还采用ThermoCalc软件进行了热力学计算模拟,辅助分析了WC分解及W与C元素在显微组织中的遗传特性。对于WC类粉末和MCrAlY粉末共用的HVOF喷涂设备,建议给MCrAlY粉末配备单独的送粉路径,以确保涂层的纯净度与质量。

Study on the Hereditary Behavior of WC Impurity Particles in MCrAlY Coatings Deposited by HVOF

In industrial thermal spray production processes, the workshop and route of powder feeding system needs to be cleaned when changing spraying materials. The powder feeding system include powder feeding tank, powder feeding tray, stirrer, powder feeding pipeline, powder feeding needle. Due to the internal structure of the powder feeding system is complex and the electrostatic adsorption effect, the residual powder in the spray system cannot be completely removed and thus affects the properties of the coating. In this paper, the high-velocity oxy- fuel (HVOF) spray technology were adopted to prepare the MCrAlY coatings on the surface of single crystal substrate, the hereditary behavior in the coatings and the interface between coating and substrate of WC impurity particles (WC-10Co4Cr) remaining in the powder feeding system was studied. The microstructure and phase composition of WC impurities in spray and heat treatment coatings were analyzed by SEM and EDS. The results showed that WC impurity particles exist in the MCrAlY coatings and would be dissolved into coating and even diffuse into single crystal substrate to form new W carbides during heat treatment and oxidation processes. As a result, the microstructure of coating and single crystal substrate has been affected and the local composition uniformity has been changed. Thermocalc software was also used to perform thermodynamic calculations for analyzing the hereditary behavior of W and C elements in the microstructures. If the WC powder and MCrAlY powder shared HVOF spraying equipment, it is recommended to provide MCrAlY powder with a separate powder feeding system to ensure the purity and quality of the coating.