Microstructure and nanoindentation measurement of residual stress in Fe-based coating by laser cladding

Laser cladding is a surface modification technique for improving surface properties. However, high residual tensile stress is always originated, which can create cracks in cladding coatings. The through-thickness residual stresses in Fe-based coating prepared by laser cladding were measured using a non-destructive nanoindentation technique. The cladding coating with a thickness of 1 mm exhibited a uniform appearance, and no crack or defect was observed. An excellent metallurgic bond was obtained between the coating and the substrate. The XRD pattern implied that the coating was mainly composed of α(Fe, Cr) solid solution, Cr₇C₃ hard phase and Fe₂B stable phase. The residual tensile stress in the cladding coating was found to increase as the increasing of the distance from coating surface. Although the tensile residual stress reaches the highest magnitude of 700 MPa up to the depth of 600 μm, no dehiscence happened. The prepared cladding coating has good plasticity and toughness, as well as low crack sensitivity.