Application of the Press-and-Sinter Method to Titanium Powder Produced by a Novel Titanium Dioxide Reduction Technology

Abstract

The Ukrainian VELTA company has developed and patented a novel technology for producing titanium metal powder through a two-stage reduction of titanium dioxide, offering an alternative to currently widespread titanium powder production methods. The key feature of the technology is the use of titanium oxide as the feedstock material, in contrast to the conventional Kroll process, which relies on titanium tetrachloride. Titanium dioxide powder is formed into feedstock elements with a specific shape, structure, and strength. The oxide constituting these elements is reduced in two stages. The first stage consists of reduction using metallic magnesium vapor and the second stage involves final deoxidation using calcium vapor. In addition to the production of pure metallic titanium, the proposed process can be employed to obtain titanium alloy powders by reducing titanium dioxide together with oxides of doping elements. The resulting powder is characterized by a low content of interstitial oxygen, nitrogen, and carbon atoms, at levels not exceeding the standard values for Ti Grade 1. The typical powder used in this study exhibits a broad particle-size distribution with a D50 of approximately 50 μm and consists of compact, irregularly shaped particles along with a significant number of very fine, nearly spherical particles smaller than 2 μm. Classification of the powder into two fractions employing an inexpensive sieving technique makes it suitable for various powder metallurgy applications. When separated into fractions below and above 45 μm, the fine fraction accounts for approximately one-third and the coarse fraction for two-thirds of the original powder weight. Previous studies have shown that the fine fraction (<45 μm) is suitable for metal injection molding (MIM). The aim of this study is to determine the suitability of VELTA’s >45 μm powder fraction for producing compact titanium via the press-and-sinter method.