Microstructural evolution and wear behaviors of NbC-reinforced Ti-based composite coating

In situ ceramic phase reinforced Ti-based composite coatings were successfully fabricated on Ti-6Al-4V alloys by laser cladding using Ti + Al + Si mixed powders with different NbC contents (0, 5, 10, 15 wt.%). The effects of different NbC content on the microstructural evolution, hardness, and wear behaviors of the Ti-based composite coatings were studied. The results showed that the phase in the cladding layer was mainly consisted of Ti₃Al, TiAl, and Ti₅Si₃ before NbC was added. After NbC was added, the TiC and Ti₃AlC₂ ceramic reinforcement phase was in suit synthesized. In addition, (Ti, Nb)C were also found. The in situ formed phases were proved beneficial to the improvement of the coating property. With the addition of NbC, the hardness of the coating is apparently increased. When the content of NbC is 15%, the maximum hardness of the coating is 1024 HV_0.2, which is almost three times that of the substrate. The coefficient of friction of the coating without NbC was 0.591. With the addition of NbC, the coefficient of friction of S2, S3, and S4 was significantly decreased to 0.450, 0.388, and 0.375, respectively. Furthermore, the addition of NbC improves the worn surface of the coatings.