Influence of heat input on bead profile and microstructure characteristics in laser and laser-hybrid welding of Inconel 617 alloy

Abstract

Bead profile and microstructure analysis are greatly influenced by heat input in any welding process. The present work provides a comprehensive comparative investigation on these aspects during Autogenous Laser welding (ALW) and Laser-MIG Hybrid welding (LHW) processes in Inconel 617 superalloy. In case of LHW, weld bead profile formed was a typical wine-cup shaped one, whereas, in case of ALW, bead profile observed was Y-type shape on account of differences in number of heat sources and intensity profiles. Weld bead width and penetration depth were found to increase with heat input in both ALW and LHW processes. The fusion zone (FZ) area of LHW was found to increase by 3 times as compared to ALW as a result of high heat input in LHW than ALW. Indeed, the addition of MIG source to laser in LHW produced wide upper bead width (trebled) as compared to ALW. Radius of curvature (ROC) at neck zone, an important bead profile characteristic for assessing liquation cracking susceptibility, was found to increase with heat input and was significantly higher in LHW than ALW due to heat stagnation at neck zone. In comparison with ALW, LHW showed a coarser columnar/cellular dendritic microstructure in FZ with segregation of inter-dendritic carbides relatively richer in Mo and Cr. Secondary dendritic arm spacing (SDAS), cooling rates and microhardness will also be discussed.

Keywords:

• Inconel 617
• laser-MIG hybrid welding
• autogenous laser welding
• heat-input
• bead-profile
• radius of curvature

Acknowledgements

The authors extend their thanks to Director, ARCI for granting permission to publish the work. We also acknowledge the experimental support provided by Mr K.V. Phani Prabhakar, Scientist, ARCI and Mr Anbu Rasu E, Technical Officer, ARCI. Authors would also like to thank DST-FIST and DST-PURSE grant for the FESEM-EDS facility and its maintenance at School of Engineering Science and Technology, University of Hyderabad.

Disclosure statement

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

Additional information

Funding

Department of Science and Technology (DST), New Delhi is acknowledged for funding the project ‘National Centre for Development of Advanced Materials and Manufacturing Processes for Clean Coal Technologies for Power Applications’ (Program code. SNCD), under which this work was undertaken.