Investigation of oxygen variation in titanium powder and metal injection molding

The control of oxygen is paramount in achieving high-performance titanium (Ti) parts by powder metallurgy such as metal injection molding (MIM). Herein, hydride-dehydride (HDH) Ti powders were modified by pre-oxidation to investigate the effect of oxygen variation on the characteristics of oxide layer on the particle surface and its resultant color feature. The results showed that the thickness and Ti dioxide level of the oxide layer on the HDH Ti powders were increased with the oxygen content, leading to the transition of color appearance from grey, brown to blue. In addition, the development of oxygen content was comprehensively studied during the MIM process using the gas-atomized (GA) Ti-6Al-4V powders. Particularly, the oxygen variation in the form of oxide layer, the change of oxygen content in the powders and the relevant parts were investigated during the process of kneading, injection, debinding and sintering. The oxygen variation was mainly concentrated in the sintering stage, and the content was increased with the increase of sintering temperature. This work provides a piece of valuable information on oxygen detecting, control and manipulation for the powder and processing in the industry of Ti powder metallurgy.