Abstract
In order to establish a commercial method to improve the wear resistance properties of Titanium, surface hardening of Titanium by Oxygen diffusion was studied. Titanium was found to be surface hardened successfully by two methods without serious scaling and embrittlement of the base metal. The first one is direct oxidation in dry oxygen followed by diffusion treatment of the oxide film in an inert atmosphere at 850°C. It was observed that the amount of Oxygen absorbed in the preliminary oxidation had to be in the range of 1 to 2 mg/cm2 to obtain a hardened layer of appreciable depth, and it was also important to degrease the specimen with care before the preliminary oxidation. The second method is heating Titanium in a molten glass bath with an appropriate viscosity at 850°C. In the glass bath, Oxygen seems to be picked up by Titanium as the result of a chemical reaction between Titanium and glass, and inward diffusion of Oxygen through Titanium takes place, producing the hardened layer. To prevent the formation of scale on the surface of Titanium, it is important to use comparatively viscous glass at the operating temperature. The viscosity of the glass seems to play an important role in causing Oxygen to diffuse into the Titanium. The properties of the hardened layers produced by these methods, both based on the diffusion of Oxygen, are quite similar: the surface hardness is about 1000 V.H.N. and the depth is about 0.3 mm when treated at 850°C for 48 hours, three times as deep as that of Titanium nitrided at the same temperature for the same period of time.
