Influence Of Oxidation On The Pressing And Sintering Properties Of Titanium Aluminide Powder

Due to the high oxygen affinity of titanium aluminides (TiAl), an oxide layer is formed on the surfaces of titanium aluminide powder particles. These oxides impede the conventional powder metallurgy process chain of powder pressing and sintering for TiAl by limiting particle cohesion and therefore green strength. To inhibit oxidation, a process atmosphere with an extremely low oxygen content (<10^-14 ppmv) was used in this work. Oxide-free blank metal surfaces on the TiAl powder particles were produced in silane-doped low-O2 atmosphere by ball milling. In order to differentiate the effect of blank metal surfaces from the effects of grinding, reference powders were exposed to the ambient atmosphere prior to compaction. After processing, the influence of the press and sintering parameters on material properties was analysed. The degree of oxidation showed significant influence on hardness, vibration resistance and splitting tensile strength but not on the sintering density.