Thermal stability and oxidation resistance of FeCrxCoNiB high-entropy alloys coatings by laser cladding

The FeCrxCoNiB (x values in molar ration, x = 0.5-3) high-entropy alloys coatings were prepared by laser cladding on an AISI 1045 steel substrate. Annealing and high temperature oxidation experiments were performed on the FeCrxCoNiB (x = 0.5-3) coatings at 900 degrees C. The phase structure, morphology, and composition of the coatings and oxidation layers were analyzed by XRD, TEM, SEM, and EDS. Results demonstrated that the FeCrxCoNiB coatings are composed of simple face-centred cubic (FCC) phase and boride. The hardness value of the coatings is significantly improved due to the boride, which is achieved 860 HV at x = 0.5. Cr is conducive to inhibiting the coarsening of boride and enhancing the resistance of coatings to high-temperature softening. The oxidation kinetics curve of FeCrxCoNiB coatings basically follows oxidation dynamic the parabolic law. The selective oxidation in the FeCrxCoNiB coatings changed from the oxidation of Fe to the oxidation of Cr as an increase in Cr content, and finally formed continuous Cr2O3 film. The high temperature oxidation resistance of the FeCrxCoNiB coatings dropped with adding boron into the coatings, which improved contributing to Cr increasing. FeCrxCoNiB coatings gain a better high temperature oxidation resistance as x >= 2 (33.3 at.%).