Laser cladding manufacturing of TiC + TiBx reinforced FeNiCrTi0.3Al0.3 high entropy alloy composite coating: Effects on corrosion and tribology

In this work, FeNiCrTi0.3Al0.3 HEA composite coatings were successfully fabricated on the surface of Ti-6Al-4V substrate by laser cladding technology. The influence mechanism of LaB6 + B4C rare earth (RE) phase on phase composition, microstructure, microhardness, corrosion resistance and tribological properties of HEA coatings were characterized. The result showed that the addition of RE phase could promote the in-situ reaction to generate TiC + TiBx. And it could alter the flow in the molten pool and produce heterogeneous nucleation. The equiaxed crystal to columnar crystal transition in the molten pool was affected. With the addition of RE phase, the maximum average microhardness of HEA composite coating reached 875.2 HV0.2, which was 2.36 times of Ti-6Al-4V substrate, indicating that the hard phase generated in-situ effectively improved the resistance of plastic deformation. The corrosion resistance of HEA composite coating strengthened by RE phase was improved as well. The corrosion property of C3 coating was optimal, and the corrosion current density was 1.79 × 10−5A/cm2, the charge transfer resistance reached to 4.48 × 105 Ω cm2, indicating that HEA composite coating could generate a passivation film which was relatively denser than the substrate and had better corrosion resistance during corrosion. Through XPS analysis, Ti, Al and Cr were found as the key elements for the passive film generation of HEA composite coating. After adding RE phase, HEA composite coating produced dense passive film and good forming quality (less cracks and pores, fine and dense grains). Compared with C0 coating, HEA composite coating could not produce occluded cell corrosion (OCC). During tribology test, the enamel layer could generate on the surface of C2 composite coatings, due to the effect of friction ball on tearing and compacting, which was of great significance to protect the coating.