Influence of process parameters on microstructural evolution, solidification mode, and impact strength in joining of stainless steel thin sheets

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ABSTRACT

Incorrect selection of process parameters corresponds to 45 % of the entire weld imperfections. Selection of process parameters becomes even more critical when the joining is reduced to micro-level. The current experimentation and computational work emphasise the influence of process parameters on joint characteristics of AISI316L and AISI310 thin sheets. Thin sheets fabricated by a micro-plasma arc welding process at different process parameters (PP) PP₁ (~524 J/cm), PP₂ (~629 J/cm), and PP₃ (~733 J/cm) are experimentally analysed to study the variation in microstructural morphology, mode of solidification, and impact toughness. The dependence of the temperature gradient (G) and solidification velocity (R) on the process parameters are also established. Microscopic images confirm the presence of equiaxed and cellular structure depending on the G/R ratio. As the cooling rate decreases, the transformation from δ-ferrite ⟶ γ-austenite is restricted, which changes the δ-ferrite percentage for different weld conditions. Elemental analysis is used to evaluate the Cr_eq/Ni_eq ratio that predicts the solidification mode using the Schaeffler diagram. The outcome of the present investigation indicates that the highest G/R and maximum G*R corresponds to enhanced joint behaviour due to favourable changes in the metallurgical properties.

KEYWORDS:

• Micro-plasma arc welding
• finite element method
• cooling rate
• solidification parameters
• microstructure

Acknowledgments

The present investigation is a result of research carried out at Indian Institute of Technology Guwahati (IIT Guwahati), Assam. The authors gratefully acknowledge the experimental facility provided by the Department of Mechanical Engineering and Central Workshop of IIT Guwahati, Assam. The authors also gratefully acknowledge the experimental facility provided by Central Research Facility (CRF) of Veer Surendra Sai University of Technology (VSSUT), Burla, Odisha, for the use of Scanning Electron Microscope (SEM). Finally, the authors thank the reviewers for many constructive suggestions.

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author(s).