Effect of Arc Plasma Sintering Process on Formation of TiO_2 Surface Layer for Ti-6AI-4V Applications

摘要

Titanium has a high affinity with oxygen forming a protective layer TiO_2. At elevated temperature, the TiO_2 layer loses its protective properties. It causes oxygen to diffuse into bulk material and makes the material become brittle, hard and has poor machinability. This experiment aims to minimize the formation of TiO_2 layer during the sintering process. The Ti-6Al-4V powder was compacted and then sintered using an arc plasma sintering (APS) with a current of 40 A, 50 A, and 60 A for 8 minutes to produce a sintered specimen protected from oxidation. As comparison, conventional sintering was carried out with an argon atmosphere with a temperature of 1100°C, 1200°C and 1300°C for 4 hours. Optical Microscope (OM), SEM-EDS, X-Ray Diffraction (XRD), density, and hardness tests were carried out to analyze the results of the sintered process. The TiO_2 layer from the result of the arc plasma sintering process is thinner than the conventional sintering. Phases obtained from the arc plasma sintering and conventional sintering are a and β titanium. The relative density obtained using the arc plasma sintering process can reach up to 99%, higher than the conventional sintering result. Hardness values from arc plasma sintering process at 40 A, 50 A and 60 A are 297, 333, and 378 HV. Meanwhile, the hardness values from conventional sintering are 414, 427, and 469 HV, respectively.