The effects of synthesis route and LaB6-doping on FeCoNiCrTi coating performance: Morphology, microstructure, microhardness and corrosion resistance

Abstract

In this work, the FeCoNiCrTi HEA coatings were fabricated on the Ti6Al4V surface via laser cladding technology. The effects of synthesis routes (different energy density, Led) and LaB6-doping on the single-track morphology, phase distribution, microstructure, microhardness and corrosion resistance of HEA coatings were comprehensively studied. Interestingly, the regulation of Led and addition of LaB6 significantly reduced the crack sensitivity and dilution rate of the coating. On the one hand, the optimized coating contributed to fine grain size when Led was 73.33 J/mm2. On the other hand, the in-situ generation of TiC, TiB2 and TiC/TiB2 composite structure played an important role in achieving the more excellent propertiy in LaB6/FeCoNiCrTi composite coating. Furthermore, the microhardness and corrosion resistance of the coatings were significantly improved owing to the ceramic phases and fine grain strengthening. Specifically, the average microhardness coating was up to 593 HV0.2. The corrosion current density (Icorr) of the coating with a Led of 73.33 J/mm2 was 4.796 × 10−6 A·cm−2, the carrier density (ND) and thickness (d) of the passivation film were 1.556 × 1022 cm−2 and 3.244 nm, respectively, indicating the best corrosion resistance in HEA coatings. In terms of LaB6/FeCoNiCrTi coating, the Icorr, ND and d were 2.400 × 10−6 A·cm−2, 1.053 × 1022 cm−2 and 4.739 nm, respectively. Consequently, the doping of LaB6 further enhanced the corrosion resistance of HEA coating.