Effect of MIG welding process parameters on microstructure and tensile behavior of hastelloy C276 using response surface methodology

The present study aims to construct a new empirical relationship for forecasting the tensile strength of Hastelloy C276 welded joints using Robotic Metal Inert Gas (MIG) welding process. The filler wire employed for this present investigation is hastelloy C276 wire. A logical approach was employed to reveal the result of MIG welding for the process parameters viz., welding current (90-110 amps), welding voltage (14.5-16.5 volts) and welding travel speed (18-22 cm min(-1)) on weld strength using central composite rotatable design matrix. The adequacy of developed model was checked using Analysis of variance (ANOVA) and interaction effect of parameters were studied using response surface methodology. From the experimental results, the sound joints yielded maximum tensile strength of 741 MPa, at welding current of 102 A, welding voltage of 15.5 V and welding speed of 19.8 cm min(-1). It may be attributed to the density distribution of precipitates in the weld region. From the ANOVA, it is observed that welding current is the most significant parameter on establishing the ultimate tensile strength followed by welding voltage and welding travel speed. Bend test was carried out in 90 degrees three point bending machine for both root and face of the welded joints and no defects like cracks or fracture are observed. Erichsen cupping test was executed on the welded joint to examine the formability and observed that the joint has good formability and ductility. Macrograghic examination have been executed to examine the weld joint quality. Microstructure have been explored with field emission scanning electron microscope to study the fusion zone, Heat Affected Zone and fractured surface. The presence of columnar dendrites at the weld zone evidences the plastic fracture during tensile testing owed to its ductile nature.