Development of a New Titanium Powder Sintering Process with Deoxidation Reaction Using Yttrium Metal
Akihiro Iizuka, Takanari Ouchi, Toru H. Okabe
Abstract
Oxygen (O) contamination in titanium (Ti) is difficult to control using conventional Ti powder-metallurgy technologies, owing to the strong affinity between Ti and O. In this study, we developed a new sintering process that can remove O from Ti by placing Ti green and yttrium (Y) in molten salt. This study demonstrates that the O concentration in Ti can be reliably controlled in the range of 200–2000 ppm O by varying aY in the Y/Y2O3 equilibrium at 1300 K in NaCl–KCl (l), such that the sintering reaction of Ti powder simultaneously proceeds. Furthermore, it is also shown that the O concentration in Ti can be reduced to 30–60 ppm O in YCl3 (l) in the sintering process, when the Y/YOCl/YCl3 equilibrium is employed. This study demonstrates the feasibility of a new sintering process that can control the O concentration in Ti to approximately 30–2000 ppm O. The process ensures economical rationality because the cost of Y metal is negligibly small in recent years. By developing this process, inexpensive high-O-concentration Ti powder can be applied for fabricating the desired low-O-concentration Ti products.