A parametric study of loose sintering of titanium powders

Abstract: There is a demand for titanium and titanium alloy spherical powders for use in powder metallurgy methods such as additive manufacturing, metal injection moulding and hot isostatic pressing. The advantages of spherical powders over irregular shaped powders are high flow properties and dense uniform packing, which are a requirement for the above mentioned processes. There are a number of powder metallurgy techniques used to make spherical powders such as atomisation and spheroidisation. The atomization process uses wires or bars as feedstocks. These feedstocks are currently produced via an ingot metallurgy route making the process to be costly. In this study, a powder metallurgy process known as loose powder sintering was evaluated as an alternative cost effective process of producing billets. Irregular shaped TiHDH -45 μm and TiHDH -150 μm powders were used for making small billets with the objective of understanding the parameters that will affect their densification and dimensional stability. Loose sintering of the TiHDH powders was carried out at temperatures ranging from 1100°C to 1500°C and sintering times of 2 to 4 hours in a Carbolite tube furnace under an argon atmosphere. The highest density of 88% was achieved after sintering TiHDH -45 μm at 1500 °C for 4 hours. TiHDH -150 μm showed to be more dimensionally stable during sintering as compared to TiHDH -45 μm. High densities and dimensional stability were difficult to achieve based on the parameters (sintering temperatures and times) studied in this work.M.Tech. (Metallurgy