Corrosion resistance of laser clad Cr-alloyed Ni₂Si/NiSi intermetallic coatings

Cr-alloyed Ni₂Si/NiSi nickel silicides coatings with a microstructure consisting of Ni₂Si primary cellular-dendrites and a small amount of interdendritic Ni₂Si/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 H₂SO₄ 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 Ni₂Si primary phase in the Cr-alloyed Ni₂Si/NiSi coatings. Alloying of the coatings with 1.5%Cr and 5.6% Cr considerably enhanced the corrosion resistance of the Ni₂Si/NiSi intermetallic coatings both under anodic polarization and immersion corrosion test conditions.