Process and properties of hydride formed on gamma titanium aluminide during cathodic charging

A cathodic charging procedure was used to study the process of the formation of the hydride layer on gamma titanium aluminides. This electrolytic process was carried out at constant current densities of 1 and 2 A/m2 for 24 h of charging in a 1N sulfuric acid solution. The hydride layer formed as a result of the charging process was observed using scanning electron microscopy. Nanohardness and microhardness of this hydride layer were also measured. Results show that the hydride forms initially as isolated islands and becomes continuous with increased charging time. The hydride layer is quite brittle and its degree of porosity increases from the metal surface outward. The thickness of the hydride layer also increases with charging current density. This is confirmed by the hardness measurements. EDS signals show the presence of the constitutive elements of gamma titanium aluminide in the hydride. ICPS analysis of the electrolyte indicates increasing metal content with increasing time of exposure probably as a result of the brittle hydride flaking off and falling into the electrolyte during the charging process.