Microstructural evolution and mechanical properties of laser repaired 12Cr12Mo stainless steel

In this study, the laser repairing (LR) method is applied to 12Cr12Mo stainless steel, and the corresponding microstructural evolution, texture characteristic, and hardness variation are investigated. A 50/50 uniaxial tensile-test is conducted, and the mechanical failure mechanism is investigated using scanning electron microscope and transmission electron microscopy. The results show that the microstructure consists mainly of martensite and tiny M₂₃C₆ carbide particles in the deposited zone (DZ), while the substrate contains tempered martensite and coarse M₂₃C₆ carbide. The high laser-power generates a cubic texture in the DZ, while the substrate maintains a texture-free matrix. From the substrate to the DZ, the hardness increases sharply at the fusion line and then decreases gradually along the building direction. The tensile-test result indicates that the overall mechanical properties of LRed 12Cr12Mo stainless steel are comparable to wrought parts. Moreover, the microvoid-coalescence fracture indicates good plasticity of the LRed samples. Using this approach, we successfully repaired a 17th-stage stator cascade of a gas turbine, which indicates that LR can be used for the type of steel investigated in this study.