Microstructure of Composite Cementation Layer on Two-Phase TiAl-Based Alloy and Its Effects on Oxidation Resistance

摘要

The effects of pack siliconization on oxidation behaviors of TiAl-based alloy were investigated. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-base alloy was greatly improved by pack cementation with 15%Si+85%Al_2O_3. The specimens before and after cycle oxidation were examined by SEM equipped with EDS. The results showed that the cementation layer is composed of Al_2O_3 outer layer and a composite inner layer of Ti_5Si_3 and an appropriate amount of Al_2O_3. No spallation or cracking occurred and the weight gain was very small after cycle oxidation at 900℃ for 238h. The microstructures of composite cementation layer after the oxidation test is similar to that before the oxidation test.