Rapid Formation of Ti Oxycarbide on the Surface of Ti Induced by Electro-Discharge-Heat-Treatment in a Low Vacuum Atmosphere

A single pulse of 2.0 to 3.5 kJ of input energy from a 450 mu F capacitor was applied in a low vacuum atmosphere to a commercially pure Ti rod. The electro-discharge process produced rapid temperature increases from 569 to 2516 degrees C in times as short as 159 mu sec, depending on the input energy. The microstructure with equiaxed alpha grains was preserved after the electro-discharge regardless of applied input energy. At the same time, the original surface of Ti rod was modified by the electro-discharge into the form of primarily titanium oxycarbide from TiO2. A much higher value of hardness that was observed at the edge of the cross-section was thus attributed to carbon- and oxygen-induced solid-solution hardening that occurred during the electro-discharge process. From these results, it is concluded that the rapid formation of titanium oxycarbide on the Ti surface can be induced in times as short as 159 mu sec by the electro-discharge process without changing its unique microstructure.