Wear behaviour and surface hardening of titanium by nitriding

Surface nitriding of pure titanium was performed using gas nitriding increase the surface hardness and improve wear performance. The effect of nitriding temperature (850-1100°C) on the microstructure, composition, and room-temperature tribological properties of the borided samples was investigated using X-ray diffraction, scanning electron microscopy, and ball-on-disc tribometry, respectively. The nitriding temperature had a large effect on the microstructure, mechanical properties, and room-temperature tribological behavior of the nitrided samples, attributed to changes in the composition with increasing nitridng temperature. The surface hardness was approximately increased firstly and then decreased with the nitriding temperature increasing. And the hardness of the diffusion layer reached to the maximum value when the processing temperature at 1050°C. At the same nitriding temperature, the indentation modulus also reached the maximum value of 270 GPa. The wear depth and wear width reached the minimum value were 14.86 μm and 637.98 μm, respectively. The worn surface of the nitrided samples at higher temperatures showed a very good wear resistance. A nitriding condition of 1050°C is considered optimal as it provides the sufficiently high hardness.