Sintering of HDH Ti powder in a solar furnace at Plataforma Solar de Almeria

The brand new technology for sintering of titanium was tested: For the first time, titanium powder was pressure less sintered under argon atmosphere at different temperatures and time, in 5 kW vertical axis solar furnace at Plataforma Solar de Almeria (PSA), Spain. The decrease of final porosity with increasing sintering temperature and time at constant heating rate is observed. The obtained results are compared with those obtained for identical green powder compacts sintered in vacuum furnace. Final porosity below 5% was achieved and shorter sintering times were observed. Radial shrinkage of samples at solar furnace is almost the same as at vacuum furnace. On the contrary axial shrinkage is 20% higher. It was proposed that this can be attributed to argon gas used during sintering and due to the different heating in solar furnace during sintering. Argon at lower temperature acts as a heat transfer medium and helps to distribute the heat more homogeneously into the powder compacts. At higher temperature it remains enclosed in the pores thereby increasing a bit final compact porosity when compared with vacuum furnace. It was further showed that the contents of O, N, H in final compacts depend predominantly on their concentration in original powder. The observed increase due to technology is 300 ppm for oxygen and 80 ppm for nitrogen. Hydrogen concentration decreased significantly. Microhardness dependence on porosity of prepared samples was also investigated and microhardness of bulk Ti prepared in solar furnace was estimated to be 282.2 ± 28.3 HV0.5.