Friction and wear behavior of TiN/Ti6Al4V composite material synthesized in-situ using laser directed energy deposition.

Laser directed energy deposition (LDED) was employed to fabricate Ti6Al4V titanium alloy and TiN/Ti6Al4V composites through nitrogen-assisted in-situ synthesis. Two fabrication routes were investigated, including direct deposition under a mixed nitrogen-argon atmosphere (TS sample) and nitrogen-assisted remelting under a pure nitrogen atmosphere (TR sample). Dry sliding tribological tests were conducted at room temperature and 300 °C. The results showed that nitrogen-assisted processing promoted the in-situ formation of TiN within the Ti6Al4V matrix. Compared with the Ti6Al4V sample, the TR sample exhibited a higher friction coefficient but significantly improved wear resistance, with the wear volume reduced by approximately 44.8% at room temperature and 78.8% at 300 °C. In contrast, the TS sample containing relatively sparse and smaller TiN particles showed limited improvement in wear resistance. At elevated temperature, all samples exhibited reduced wear loss, which was likely associated with oxidation-assisted surface protection during sliding. Microstructural observations indicated that the remelting-assisted process promoted the formation of larger TiN particles with a denser distribution in the TR sample, significantly influencing the wear evolution behavior. However, the tribological response was likely affected by the combined effects of TiN reinforcement and processing-induced microstructural evolution associated with different thermal histories. This study demonstrates that nitrogen-assisted remelting is an effective approach for improving the tribological performance of Ti6Al4V alloys and provides insight into the influence of TiN distribution on wear behavior in LDED-fabricated titanium matrix composites.