Effect of LaB6 doping on the microstructure, microhardness and corrosion behavior of laser cladded FeCoNiCrMo coating on Ti6Al4V

Abstract

In order to improve the microhardness and corrosion resistance of Ti6Al4V alloy, LaB6 powders was added to the FeCoNiCrMo high entropy alloy coatings fabricated by laser cladding on Ti6Al4V. The microstructure, corrosion resistance and microhardness of LaB6/HEA coatings were analyzed by SEM, EDS, XRD, TEM and performance characterization equipment. The results showed that the appropriate content of LaB6 (2 wt%) could significantly reduce the cracking sensitivity of the coating, and in-situ synthesized La2O3 refined the microstructure and achieve fine grain strengthening. The reduction of cracks and refinement of the microstructure improved the corrosion resistance of HEA. At the LaB6 content of 2 wt%, the corrosion current density of the coating was 2.164 × 10−6 A·cm−2, passive potential was 1.339 V, and the number and size of pitting on the surface of the sample were the lowest, indicating that the passivation film had the strongest resistance to corrosive media. In addition, at the amount of LaB6 addition of 2 wt%, the microhardness of the coating could reach up to 987 HV0.3, which could be attributed to the in-situ synthesis of the ceramic phase TiBX and the refinement of the grains.