Spontaneous Formation of Titanium Nitride on the Surface of a Ti Rod Induced by Electro-Discharge-Heat-Treatment in an N2 Atmosphere

A single pulse of 2.0 to 3.5 kJ of input energy from a 450 mF capacitor was applied to a commercially pure Ti rod in a N2 atmosphere. The surface of the Ti rod transformed from TiO2 into titanium nitride in times as short as 159 msec, providing a bimodal morphology of the cross-section. A much higher value of hardness that was observed at the edge of the cross-section was attributed to nitrogen-induced solid-solution hardening that occurred during the electrical discharge process. The activation energy (Ea) for the diffusion process was estimated to be approximately 86.9 kJ/mol. Results show that the electrical discharge process is a possible potential method for the nitriding of Ti; advantages include a short processing time and control of the nitrided layer without dimensional changes