Residual Stress of Repair Welded 12Cr12Mo Steel Blade Surface after Composite Shot Peening

The surface of 12Cr12Mo martensitic heat-resistant steel gas turbine blade repaired by repair welding was treated by ceramic bead+glass bead composite shot peening. The effects of composite shot peening on residual stress, microstructure and hardness at different positions of blade surface were studied. The results show that a high level of residual compressive stress field was introduced into all areas of the blade surface after composite shot peening; the change of residual stress in the repair welding area was the most obvious, and the residual compressive stress was the largest, which changed from the tensile stress in the range of 35-224 MPa before composite shot peening to the compressive stress in the range of -937——884 MPa. After composite shot peening, the X-ray diffraction half-height width of blade surface decreased with increasing distance from the surface, and the half-height width of X-ray diffraction of repair welding area surface was higher than those of heat affected zone and substrate, indicating that the degree of microstructure deformation decreased with increasing distance from the surface, and the microstructure deformation in repair welding area was the largest, and the microstructure was the finest. The hardness of the blade surface decreased with increasing distance from the surface, and the surface hardness of repair welding area was 621 HV, which was higher than 482 HV of heat affected zone and 431 HV of substrate.