铌硅化物基超高温合金Si-Y_2O_3共渗涂层的组织及裂纹形成

采用分别于1 050、1 150、1 250 ℃保温10 h的Si-Y_2O_3包埋共渗工艺,在铌硅化物基超高温合金表面制备了Y改性的硅化物涂层.利用SEM、EDS和XRD等方法分析了Y对涂层形貌及裂纹形成的影响,并与相同温度和时间下单独渗Si涂层的组织进行了对比.结果表明,涂层外层上部为分布均匀致密的(Nb,M)Si_2柱状晶,外层下部为疏松的(Nb,M)Si_2等轴晶;渗剂中添加质量分数为0.75%的Y_2O_3可以细化涂层组织,且当渗剂中的w(Y_2O_3)为0.50%～0.75%时,所制备涂层的纵向裂纹和横向裂纹的总长度均较小.

Microstructure and Crack Formation of the Si-Y_2O_3 Infiltration Coating on Nb-Si-based Ultrahigh-temperature Alloy

Si-Y_2O_3 infiltration coating was prepared from the Nb-Si-based ultrahigh-temperature alloy surface by the pack infiltration of heating for 10 h at 1 050 ℃,1 150 ℃ and 1 250 ℃,respectively.The effects of Y element on coating morphology and crack formation were investigated by SEM, EDS and XRD.Both prepared by the pack infiltration at the same temperature and duration,Si-Y_2O_3 infiltration coating was compared with single Si infiltration coating. The results show that the upper part of the outer coating layer is composed of (Nb,M)Si_2 columnar grains,and the lower part composed of (Nb,M)Si_2 equiaxed grains.The coating microstructure can be refined obviously by adding 0.75% (mass fraction) Y_2O_3 to the pack mixture. The total length of either vertical cracks or horizontal cracks is relatively small when the Y_2O_3 amount in pack mixture is in the range from 0.5% to 0.75%.