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<p>This study investigates the phase transformations and mechanical properties resulting from Nd: YAG Pulsed Laser Welding (PLW) of 2&#xa0;mm thick Haynes 188 superalloy sheets, widely recognized for their exceptional high strength and better weldability. This research presents the butt welding under the influence of varying laser pulse frequencies (5, 8, and 10&#xa0;Hz). The experiment shows the pulse frequency primarily influences the weld overlapping factor (at 5&#xa0;Hz: 23.3%; 8&#xa0;Hz is 54.1%; and 10&#xa0;Hz: 63.3%). The morphology studies of the base metal (BM) having equiaxed grains with twin boundaries and the average grain size of 19.52&#xa0;μm. The fusion zone mainly shows the FCC gamma (<i>γ</i>) phase matrix structure and observes the columnar dendrites due to the epitaxial grain growth that occurred from the BM during PLW. At a pulse frequency of 10&#xa0;Hz, the average grain size was 50.43&#xa0;μm, which is 35.35% less than 8&#xa0;Hz. Also, the existence of directional solidification in FZ was confirmed by EBSD. The tensile strength at a pulse frequency of 10&#xa0;Hz is 974.03 ± 15&#xa0;MPa, and the hardness is 331.21 ± 5 HV more compared to the 8&#xa0;Hz due to the presence of smaller grains. The pulse frequency of 8&#xa0;Hz has lower tensile strength (9.90%) and average microhardness (5.2%) than the limited 10&#xa0;Hz. Tensile test results and fractography analysis of the welded samples confirm the ductile fracture. The results obtained from the present study are applied for the PLW characteristics of Haynes 188 superalloy for high-temperature applications.</p>

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Influence of Pulse Frequency on the Metallurgical and Mechanical Characteristics of Welded Joints for Haynes 188 Superalloy by Pulsed Laser Welding

  • 期刊论文

  • 发表日期：

    2025年10月29日

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  • Venkatesh Govindan,
  • Anand Ramanathan,
  • Muthukannan Duraiselvam

摘要

This study investigates the phase transformations and mechanical properties resulting from Nd: YAG Pulsed Laser Welding (PLW) of 2 mm thick Haynes 188 superalloy sheets, widely recognized for their exceptional high strength and better weldability. This research presents the butt welding under the influence of varying laser pulse frequencies (5, 8, and 10 Hz). The experiment shows the pulse frequency primarily influences the weld overlapping factor (at 5 Hz: 23.3%; 8 Hz is 54.1%; and 10 Hz: 63.3%). The morphology studies of the base metal (BM) having equiaxed grains with twin boundaries and the average grain size of 19.52 μm. The fusion zone mainly shows the FCC gamma (γ) phase matrix structure and observes the columnar dendrites due to the epitaxial grain growth that occurred from the BM during PLW. At a pulse frequency of 10 Hz, the average grain size was 50.43 μm, which is 35.35% less than 8 Hz. Also, the existence of directional solidification in FZ was confirmed by EBSD. The tensile strength at a pulse frequency of 10 Hz is 974.03 ± 15 MPa, and the hardness is 331.21 ± 5 HV more compared to the 8 Hz due to the presence of smaller grains. The pulse frequency of 8 Hz has lower tensile strength (9.90%) and average microhardness (5.2%) than the limited 10 Hz. Tensile test results and fractography analysis of the welded samples confirm the ductile fracture. The results obtained from the present study are applied for the PLW characteristics of Haynes 188 superalloy for high-temperature applications.