Research on the multi environmental corrosion characteristics and mechanism of B4C doped Fe–Cr–Ni composite coating produced by laser cladding

Abstract

Different Fe-Cr-Ni composite coatings doped with B 4 C were produced on the surface of Cr12MoV steel by laser cladding. Special attention was paid to the effects of B 4 C content on the phase composition, microstructure, and corrosion resistance of the cladded layers. The results indicated that the Fe-Cr-Ni composite coating was primarily composed of α-(Fe, Cr) and γ-(Ni-Cr-Fe) solid-solution phases, as well as Fe 2 B, M 7 C 3 , Fe 3 Si and M 23 C 6 phases. Once the B 4 C content increased to 10 wt.%, the microstructure of the cladding layer became coarse and exhibited the prominent carbide agglomeration. The composite coatings with different B 4 C contents exhibited superior corrosion resistance compared to the pure substrate in both 3.5 wt.% NaCl and 1 mol/L HCl solutions. Furthermore, as the B 4 C content increased, the corrosion resistance of the coating initially increased and then declined. In particular, the Fe-Cr-Ni composite coating with an 8 wt.% B 4 C content experienced the pronounced passivation in the corrosive media and possessed the optimal corrosion resistance due to the synergistic effect of the passive film and carbide barrier layer.