TiAl合金表面Si-Co-Y扩散渗层的高温抗氧化性能

High-temperature Oxidation Behavior of Si-Co-Y co-deposited Coating Prepared on a TiAl Alloy by Pack Cementation Process

摘要:

采用扩散共渗方法在TiAl合金表面制备了Si-Co-Y渗层,分析了渗层的组织结构、形成机理及其在950 ℃时的抗氧化性能。所制备的Si-Co-Y渗层组织致密,呈多层结构：主要由TiSi₂表层,TiSi₂+Ti₅Si₄+Ti₅Si₃混合组成的外层,Ti₅Si₃中间层和TiAl₂内层组成；渗层生长过程由Si的向内扩散控制,且遵循先沉积Si后沉积Co的有序过程。氧化实验结果表明,Si-Co-Y渗层具有良好的高温抗氧化性能,在950 ℃氧化100 h后表面形成了由SiO₂, TiO₂和Al₂O₃组成的保护性氧化膜；该氧化膜的生长遵循抛物线规律,氧化增重的抛物线速率常数约为6.3×10_-2 ^mg₂^/cm₄ ^h_1/2^,较基体合金低约一个数量级。

Abstract:

Si-Co-Y co-deposited coating was prepared on the surface of TiAl alloy by pack cementation process. The microstructure, formation mechanisms and oxidation performance at 950 ℃ of the coating were analyzed. The obtained Si-Co-Y co-deposition coating is compact and possesses multilayer structure: mainly composed of a TiSi₂ superficial zone, a TiSi₂ and Ti₅Si₄ mixed outer layer, a Ti₅Si₃ middle layer and a TiAl₂ inner layer. The growth of the Si-Co-Y co-deposited coating is controlled by inward diffusion of Si, and followed an orderly process of depositing Si first and then Co. High-temperature oxidation tests show that the Si-Co-Y co-deposited coating has good anti-oxidation resistance, due to the formation of a protective oxide scale that composed a mixture of SiO₂, TiO₂ and Al₂O₃. The growth of the oxide scale on the coating followed a parabolic law, and the parabolic rate constant of oxidation weight gains is about 6.3×10_-2 ^mg₂^/cm₄^h_1/2^, lower than that of the TiAl substrate by about one order of magnitude.