Abstract
Alloy 718 is a high temperature nickel base superalloy, broadly used in the aerospace sector due to its exceptional strength at elevated temperature. It is more vulnerable to the segregation of alloying elements and development of laves phase in fusion zone (FZ) owing to the high heat input in Tungsten Inert Gas (TIG) welding which drastically deteriorates the yield strength and ductility of welded joints. To obviate this problem, a newly emerged InterPulsed TIG welding process, principally characterized by electromagnetic constriction and high frequency pulsation of arc, was employed to make the joints of thin Alloy 718 sheets. The three-dimensional (3D) response surface graphs were developed using Response Surface Methodology (RSM) to identify the InterPulsed TIG welding parameters giving maximum yield strength and elongation. The yield strength and elongation of joints were predicted from the parametric mathematical models. The mathematical relationships were also developed to predict yield strength and elongation from volume fraction (%) of laves phase. The InterPulsed TIG welded joints exhibited a maximum of 94.45% and 82.89% of base metal yield strength and elongation. It is attributed to the grain refinement in FZ and substantial evolvement of laves phase in finer discrete morphology.
Published Version
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