Corrosion resistance of laser clad Cr-alloyed Ni 2Si/NiSi intermetallic coatings

Abstract

Cr-alloyed Ni 2Si/NiSi nickel silicides coatings with a microstructure consisting of Ni 2Si primary cellular-dendrites and a small amount of interdendritic Ni 2Si/NiSi eutectics were fabricated on a substrate of 0.2%C carbon steel by laser cladding using Ni–Si–Cr elemental powder blends as the precursor materials. Influence of Cr-alloying on corrosion resistance of the coatings was investigated under anodic polarization and immersion corrosion test conditions in H 2SO 4 and NaCl solutions. Results showed that addition of 1.5%Cr has little effect on the microstructure, while alloying with 5.6%Cr significantly increased the volume fraction of Ni 2Si primary phase in the Cr-alloyed Ni 2Si/NiSi coatings. Alloying of the coatings with 1.5%Cr and 5.6% Cr considerably enhanced the corrosion resistance of the Ni 2Si/NiSi intermetallic coatings both under anodic polarization and immersion corrosion test conditions.