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<p>After the welding forming process, 316&#xa0;L stainless steel welded joints have defects such as microstructural non-uniformity and coarse grains. These defects lead to reduced mechanical properties and service life of the welded structures, seriously affecting their reliability for safe application. To improve the quality of 316&#xa0;L laser welded joints, ultrasonic impact treatment (UIT) was performed, and the effects of UIT on tensile properties, microhardness, nano-hardness, microstructure, and fracture morphology were analyzed. The results show that when the ultrasonic impact current is 2.0 A, the tensile strength increases by 30.7&#xa0;MPa, the yield strength increases by 37.3&#xa0;MPa, and the elongation increases by 13.6%, achieving simultaneous improvement in the strength and ductility of the welded joints. The tensile fractures before and after UIT both exhibit characteristics of ductile fracture. After UIT, the dimple size in the fibrous zone of the fracture increased, and the second-phase particles were uniformly refined, verifying the overall improvement in tensile properties. Meanwhile, UIT introduced high-frequency energy causing plastic deformation, which led to lattice distortion, promoting grain boundary migration and grain refinement, thereby significantly enhancing both microhardness and nano-hardness. The microhardness of the base metal (BM) can be increased to about 300&#xa0;HV<sub>1.0</sub>, while the weld metal (WM) can reach approximately 310&#xa0;HV<sub>1.0</sub>. The result of nano-hardness tests indicated that UIT improved the load-bearing capacity and resistance to plastic deformation of the welded joints. Applying UIT technology to 316&#xa0;L stainless steel welded structures can improve the quality of joints manufactured by laser welding.</p>

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Study on the Effects of Ultrasonic Impact Treatment on Microstructure and Properties of 316L Laser Welded Joints

  • 期刊论文

  • 发表日期：

    2025年4月24日

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  • Guanhua Xu,
  • Feilong Liu,
  • Liqiang Gao,
  • Bangping Gu,
  • Yuchen Yang,
  • Hu Zhou

摘要

After the welding forming process, 316 L stainless steel welded joints have defects such as microstructural non-uniformity and coarse grains. These defects lead to reduced mechanical properties and service life of the welded structures, seriously affecting their reliability for safe application. To improve the quality of 316 L laser welded joints, ultrasonic impact treatment (UIT) was performed, and the effects of UIT on tensile properties, microhardness, nano-hardness, microstructure, and fracture morphology were analyzed. The results show that when the ultrasonic impact current is 2.0 A, the tensile strength increases by 30.7 MPa, the yield strength increases by 37.3 MPa, and the elongation increases by 13.6%, achieving simultaneous improvement in the strength and ductility of the welded joints. The tensile fractures before and after UIT both exhibit characteristics of ductile fracture. After UIT, the dimple size in the fibrous zone of the fracture increased, and the second-phase particles were uniformly refined, verifying the overall improvement in tensile properties. Meanwhile, UIT introduced high-frequency energy causing plastic deformation, which led to lattice distortion, promoting grain boundary migration and grain refinement, thereby significantly enhancing both microhardness and nano-hardness. The microhardness of the base metal (BM) can be increased to about 300 HV1.0, while the weld metal (WM) can reach approximately 310 HV1.0. The result of nano-hardness tests indicated that UIT improved the load-bearing capacity and resistance to plastic deformation of the welded joints. Applying UIT technology to 316 L stainless steel welded structures can improve the quality of joints manufactured by laser welding.