Effect of a small increase in the Ni content on the properties of a laser surface clad Fe-based alloy

Two Fe-based alloys with a small variation in the Ni content, Fe-15.2Cr-5.1Ni and Fe-15.7Cr-7.1Ni (wt.%), were fabricated on a martensitic stainless steel 1Cr13 substrate by laser surface cladding (LSC) using a CO2 laser and Ar shielding gas that was blown into a molten pool. Both LSC alloys exhibited typical rapid directional solidification structures. However, 2 wt.% Ni increase led to ∼9% increase in the weight fraction of austenite, and ∼5% increase in the area proportion of interdendritic regions, which contained the higher Cr contents. These microstructural changes caused a great reduction in the microhardness and great improvements in the resistance to electrochemical corrosion in 0.5 M H2SO4 solution and high temperature oxidation in air at 900 °C. The reasons for these differences are discussed in detail.