Full length article Study on uni-axial tensile strength properties of Ytterbium fiber laser welded Hastelloy C-276 sheet Kalinga Simant Bal a , Jyotsna Dutta Majumdar b , Asimava Roy Choudhury a,⇑ a Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur, West Bengal 721302, India b Department of Metallurgical & Materials Engineering, Indian Institute of Technology, Kharagpur, West Bengal 721302, India article info Article history: Received 11 January 2018 Received in revised form 24 May 2018 Accepted 12 July 2018 Keywords: Hastelloy C-276 Laser beam welding Ytterbium fiber laser Tensile test abstract Failure of as-welded Hastelloy C-276 specimen in uni-axial tensile test has been reported to occur at the weld joint with around 50% reduction in elongation length relative to that of as-received Hastelloy C-276 specimen. The proposed reason for such an occurrence is due to the micro-segregation of elements during solidification of the weld zone. Micro-segregation causes formation of brittle inter-metallic phases, mainly at the grain boundaries of the weld zone, leading to a change in deformation behavior of the welded spec- imen. Reduction in the linear heat input required for welding tends to reduce micro-segregation. Ytterbium fiber laser with its higher melting efficiency, requires lower linear heat input for welding, in comparison to other sources of heat. In the present investigation, Ytterbium fiber laser has been used for welding of 3 mm thick Hastelloy C-276 sheet and the tensile strength properties of the as-welded spec- imens have been studied. It is observed that the fiber laser as-welded specimens fail at the base metal, and the percent elongation is found to be increase twice as compared to that of previous reported literatures. Analysis of the fiber laser as-welded specimen showed (a) Reduction in micro-segregation within the weld zone due to high cooling rate (=1000 °C/s) of the melt pool; (b) Cooling time through the sensitization temperature range at the heat-affected zone was found to be 1.01 s as compared to 360 s required for pre- cipitation of inter-metallic phase; (c) Ductile nature of the weld zone due to presence of inclined cellular dendrites at the weld centerline facilitating plastic deformation; and (d) Significant increase in elongation of heat-affected zone grains as compared to that of the base metal grains. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Application of Hastelloy C-276 as structural components in chemical processing industries requires defect-free and high- strength weld joints [1]. Hastelloy C-276 has been reported to have good weldablity property, however welded specimen have few limitations such as hot cracking tendency, failure at weld joint, and reduction in percent elongation. In the survey of literature of welding of Hastelloy C-276 and some allied Ni-base and Ni-rich alloys, it was found that investigations have been carried out in some specific directions to understand the limitations as men- tioned above. Following that, a brief survey is presented as below. 1.1. Linear heat input in welding Gas tungsten arc welded (GTAW) Hastelloy C-276 specimen face the problem of hot crack tendency due to formation of inter-metallic phases because of micro-segregation in the weld zone [2]. Razavi [3] has reported that lower heat input required for laser beam welding provides advantage over conventional fusion welding processes. Taheri et al. [4] carried out surface re- melting of aged Inconel 617 by gas tungsten arc (GTA) and pulsed Nd:YAG laser beam, and observed that cracks were produced in specimen treated by GTA process, while no cracks were observed in laser treated surface. Similarly, Authors [5,6] have reported improvement in tensile strength properties due to decrease in the heat input at the weld zone. Manikandan et al. [7] carried out continuous Nd:YAG laser beam welding of Hastelloy C-276 sheet using lower value of heat input, and observed that ultimate tensile strength of the welded specimen was comparable to that of the base metal. However, they observed that welded specimen fractured at the weld zone. 1.2. Grain morphology at weld centreline Study carried out by Kumar et al. [8] on pulsed Nd:YAG welding of different grades (SS 304 and SS 316) of stainless steel shows that https://doi.org/10.1016/j.optlastec.2018.07.018 0030-3992/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: archie@mech.iitkgp.ernet.in (A. Roy Choudhury). Optics and Laser Technology 108 (2018) 392–403 Contents lists available at ScienceDirect Optics and Laser Technology journal homepage: www.elsevier.com/locate/optlastec