Thermal Fatigue Testing System for the Study of Gamma Titanium Aluminides in Gaseous Environments

To critically assess the thermal fatigue resistance of γ-titanium aluminides in hydrogen and other gases, a thermal fatigue test system and associated procedures were developed. The test equipment consisted of an environmental chamber, a rigid test fixture with fixed grips, and a thermal controller. Direct electrical resistance heating was used to heat the specimen, and cooling was accomplished by a chilled gas jet. Characterization of the thermal-mechanical features of the equipment showed that the system allows for rapid heating and cooling rates with acceptable control of the thermal stresses and has excellent repeatability between cycles.

Proof tests were performed on a Ti-48Al-2Cr alloy in helium, hydrogen, and air, with temperature cycling between 25 and 900°C and a preload equal to 50% of the material's yield strength. The results showed that the equipment and test method developed here are an effective tool for material evaluation, specifically for the critical assessment of materials for high temperature applications in hydrogen and hydrogenous gases.