A comparative study of the dynamic elastic moduli of gamma titanium aluminide and Inconel 718 under the influence of hydrogen.

摘要

The material gamma titanium aluminide, gamma-TiAl (Ti-46.5A1-4(Cr, Nb, Ta and B), has excellent properties that make it fit for several uses, including application as an advanced turbine material in the aerospace industry where hydrogen is used as fuel. Any variation in the properties of the material as a result of exposure to hydrogen will have important consequences in the design of turbine structures made of gamma-TiAl. The objective of this investigation is to characterize the effect of atomic hydrogen on the dynamic modulus of elasticity of gamma-TiAl and of Inconel 718, which is a material currently used in turbine applications. For this purpose a cathodic charging procedure was used for specimens of convenient dimensions. This electrolytic process was carried out at constant current densities of 1 A/m2 and 2 A/m2 for 24 hours of charging. Before and after this charging process, a vibration-based technique for measuring the change in the modulus of elasticity was used. The hydride layer formed as a result of the charging process was characterized using different techniques such as scanning electron microscopy, nano and micro-hardness measurements and inductively coupled plasma emission spectrometry. It is concluded from the experimental data that hydrogen has a degrading effect on the modulus of elasticity of the gamma-TiAl alloy and has virtually no effect on the elastic modulus of Inconel 718.