Microstructure, Growth Kinetics and Some Mechanical Properties of Boride Layers Produced on Pure Titanium by Molten-Salt Boriding

To modify the surface properties of pure titanium, boride layers had been fabricated by the boron molten-salt diffusion on pure titanium surfaces in the temperature range of 900-1100 A degrees C for 5- to 30-h treatments. The results demonstrated that the boride layers were mainly composed of TiB whiskers and TiB2 layers without the rutile titanium oxide TiO2. Two diffusion models were introduced to model the growth kinetics of boride layers. The parabolic growth constants and the boron diffusion coefficients were obtained. The boron activation energies for TiB2 and TiB were 225.617 and 165.266 kJ mol(-1), respectively. The surface microhardness of the borided titanium decreased with the increase in distance from the surface. The results of wear tests indicated that the wear properties had been improved significantly compared to the pure titanium under dry sliding conditions.