Spark plasma sintering assisted rapid growth of titanium boride layers on titanium: Microstructures and growth kinetics

To increase the surface hardness of titanium (Ti), the boride layers composed of TiB2 and TiB, were prepared on the CP-Ti substrate by spark plasma sintering (SPS) technique with micro-TiB2 powders as boride source. Effects of sintering temperature and holding time on the microstructure, thickness, growth kinetic and hardness of boride layers were investigated. Experimental results showed that the boride layers were composed of a continuous TiB2 top-layer and a TiB nano-whisker sub-layer. The maximum thickness of boride layers of TiB2 and TiB were 2.24 +/- 0.49 mu m and 15.63 +/- 6.97 mu m, respectively. The activation energy of boron atom for the SPS boride process was calculated to be 386.49 kJmol(-1) for the TiB2 layer and 343.57 kJmol(-1) for the TiB layer, which indicates that the SPS can provide enough energy that required in the surface treatment. Boride layers can grow well at a vacuum level of 6 Pa in the SPS. The borided Ti is about six times the hardness of the pure Ti. Boron atoms in the TiB2 powders were activated by the high temperature and plasma, then reacted with Ti to form TiB nano-whiskers. The holding time of the present method was significantly shorter than other boriding processes. This SPS process provides a new approach for boriding of Ti and its alloys.

Automated summary

This study prepared boride layers composed of TiB2 and TiB on a CP-Ti substrate using the SPS technique. The effects of sintering temperature and holding time on the microstructure, thickness, growth kinetic, and hardness of the boride layers were investigated. It was found that the boride layers consisted of a continuous TiB2 top-layer and a TiB nano-whisker sub-layer, with maximum thicknesses of 2.24 μm and 15.63 μm, respectively. The SPS process provided enough energy for the boriding treatment, and the holding time required was significantly shorter than other methods.