Narrow-gap laser-TIG hybrid welding process and mechanical properties of 0Cr13Ni5Mo stainless steel

To address the issues of insufficient impact toughness of the weld metal and low welding efficiency of the traditional arc welding in Pelton turbine runners, a narrow-gap laser-TIG hybrid welding process was proposed in this paper. The influence of process parameters on the weld formation quality in narrow-gap grooves was investigated through a single-factor controlled variable method, and the microstructure and mechanical properties were analyzed. The results indicate that the weld exhibits good formation without defects when the laser power is 3000 W; the welding current is 320 A; the welding speed is 0.2 m/min; the wire feeding speed is 5 m/min; the oscillation angle is 10°, and the deposition efficiency is 2.7 kg/h. By using these optimized welding process parameters, high-quality welding is achieved on a 50 mm-thick super martensitic stainless steel mock-up. Different regions of the weld exhibit distinct microstructural characteristics due to the variations in thermal cycles, and the middle region forms a uniform and fine equiaxed grain structure after experiencing multiple thermal cycles and tempering effects. The microhardness of the weld fluctuates in the range of 303 ~ 320 HV10; the yield strength reaches 937 MPa ± 58 MPa, while retaining good plasticity. The overall impact toughness of the weld is excellent, and the impact absorbed energy at 0 ℃ is 303 J ± 21 J. In summary, the narrow-gap laser-TIG hybrid welding technology can significantly improve the welding quality and efficiency of the runner, providing a new technical path and practical guidance for the welding operations of large-scale runners.