Characteristics and wear performance of borided Ti6Al4V alloy prepared by double glow plasma surface alloying

• Borided layers were prepared on Ti6Al4V by double glow plasma alloying.
• The borided layer consists of a boride layer and a boron diffusion zone.
• The improvement of surface hardness is mainly due to TiB compound and precipitates.
• The layer exhibited excellent bonding strength and impact resistance.
• Plasma boriding on Ti6Al4V can greatly improve wear resistance under low loads.

Many hard or super hard coatings have been successfully prepared on titanium alloys using varieties of technologies for improving their wear resistance. Sometimes, however, enough toughness of the modified layers on titanium alloys is also demanded under some conditions, such as with dynamic impact loads. In this study, a 2 μm thick uniform boride layer, composed of TiB, TiB2, Ti3B4, Fe3B and FeB phases, was formed on the surface of Ti6Al4V alloy using a double glow plasma surface boriding technique with FeB compound solid as precursor. A boron diffusion zone, beneath the boride layer, appeared with a thickness of more than 6 μm consisting of interior-oriented needle-like TiB precipitates within the base. The boride layer and the boron diffusion zone composed jointly the whole borided layer, which presented excellent toughness and bonding strength in scratch and impact tests. The surface hardness of the borided Ti6Al4V alloy was about 8.38 GPa. Compared to as-received Ti6Al4V alloy, the borided alloy exhibited significant improvement of wear resistance, about 35 times, against corundum ball with low normal loads under dry sliding conditions.