Structural characteristics and high-temperature tribological behaviors of laser cladded NiCoCrAlY-B4C composite coatings on Ti6Al4V alloy

In order to improve the hardness and tribological performance of Ti6Al4V alloy, NiCoCrAlY-B4C composite coatings with B4C of 5%, 10% and 15% (mass fraction) were fabricated on its surface by laser cladding (LC). The morphologies, chemical compositions and phases of obtained coatings were analyzed using scanning electronic microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD), respectively. The effects of B4C mass fraction on the coefficient of friction (COF) and wear rate of NiCoCrAlY-B4C coatings were investigated using a ball-on-disc wear tester. The results show that the NiCoCrAlY-B4C coatings with different B4C mass fractions are mainly composed of NiTi, NiTi2, alpha-Ti, CoO, AlB2, TiC, TiB and TiB2 phases. The COFs and wear rates of NiCoCrAlY-B4C coatings decrease with the increase of B4C content, which are contributed to the improvement of coating hardness by the B4C addition. The wear mechanisms of NiCoCrAlY-B4C coatings are changed from adhesive wear and oxidation wear to fatigue wear with the increase of B4C content.