铌基超高温合金表面包埋Si-Y共渗涂层的显微组织

MICROSTRUCTURE OF Si-Y CO-DEPOSITION COATING PREPARED ON A Nb-BASED ULTRAHIGH TEMPERATURE ALLOY BY PACK CEMENTATION PROCESS

通过在1050和1150℃包埋Si-Y共渗5—20 h的方法在铌基超高温合金上制备抗氧化涂层,对涂层结构、相组成和形成过程进行了分析.结果表明:涂层主体为(Nb,X)Si_2(X=Ti,Cr,Hf),向内依次为(Nb,X)_5Si_3过渡层和富Al扩散区;不同共渗条件下制备的涂层具有相似的结构,涂层生长的动力学曲线符合抛物线规律.能谱的半定量分析表明,渗层中的Y含量随共渗温度的升高增加显著,而随共渗时间的延长增加缓慢.

Si-Y co-deposition coatings on an advanced Nb-based ultrahigh temperature alloy were prepared by pack cementation process at 1050 and 1150 ℃ for 5-20 h, respectively. The coating structure, phase constituent and structure formation of the coatings have been analyzed. It has been found that the coating is mainly composed of compact upper layer and loose lower layer （Nb, Z）Si2 （X represents Ti, Cr and Hf）, a （Nb, X）5Si3 transitional layer and an Al-rich diffusion zone just above the substrate. The coating growth kinetics accord with the parabolic laws. The Al-rich zone has a suppressive effect on the growth of the coating. EDS analyses revealed that the content of Y in the coating increased evidently with rising co-deposition temperature, but increased slowly with prolonging co-deposition time.