Effect of Laser Remelting Energy Density on Microstructure and Properties of Laser Cladding IN 625 Layer

To enhance the comprehensive performance of laser cladding coatings, IN 625 alloy coatings were fabricated on Q345R steel substrates via laser cladding technology, followed by laser remelting treatment under varying laser energy densities. In this paper, the differences in microstructure and properties of the cladding layers without remelting and after laser remelting with different laser energy densities are studied. The experimental results show that laser remelting could effectively improve the surface roughness of the cladding layer. With the increase in laser energy density, the surface roughness initially decreased from 20.82 μm to 7.04 μm at 8 J/mm2 and then increased to 10.28 μm at 12 J/mm2. After laser remelting, the grain size of the cladding layer became more uniform, the number of equiaxed crystals increased, and the columnar crystals in the remelting area were broken to form short, rod-like columnar crystals. With the increase in laser energy density during remelting, the microhardness of the cladding layer gradually increased. The average microhardness of the cladding layer after remelting with 12 J/mm2 laser energy density was about 265 HV0.2, and the microhardness distribution was more uniform. With the increase in laser energy density, the corrosion resistance of the cladding-layer surface changed from an increase to a decrease. After remelting with a laser energy density of 8 J/mm2, the cladding layer showed higher corrosion resistance, with the highest corrosion potential of −0.41 V and the minimum corrosion current density of 0.562 μA/cm2.