The Effort to Lower Titanium Oxidation in the Sintering Process of Titanium Alloy: A Review

Titanium alloy Ti-6Al-4V has a combination of mechanical properties for implants such as good ductility, high resistance to corrosion, and good biocompatibility. However, the use of this alloy is limited due to low oxidation resistance at high temperatures from the Metal Injection Molding (MIM) sintering process where oxygen reacts with titanium forming TiO2. The formation of TiO2 gave a negative influence in terms of lowering the ductility so as to make the material fragile (embrittlement). In addition, TiO2 will form pores on the implant and reduce the density of Ti-6Al-4v. Some researchers sought to reduce the formation of TiO2 in several ways, including the reactive oxygen scavenger of rare earth (RE) and the oxygen-stabilized compounds and the control and arrangement of sintering atmospheres. In addition, the use of the new sintering method Arc Plasma Sintering (APS) gives refinement on the surface of sintering results and the short sintering time of APS can minimize the occurrence of oxidation reactions. Unfortunately, there has not been any research that gives a new method on the MIM process to minimize the formation of TiO2. Therefore, this paper aims to review new methods in the MIM process by adding oxygen scavenger from rare earth which is reactive based on Gibbs free energy diagram of standard oxide formation so that the elements and compounds can form the rare earth oxide with a brief variety of sintering time using APS in a controlled argon atmosphere. This new method is expected to provide a solution to reduce the formation of TiO2 in Ti-6Al-4V alloy so that the required mechanical properties as a condition of implant material can be maintained.