The purpose of the present work is to investigate the microstructural features and ability to withstand aggressive environment of the bimetallic joint between hastelloy C-276 and advance austenitic stainless steel 254 SMO fabricated by keyhole plasma arc welding using high nickel ERNiCrMo-4 filler. Optical microscopy revealed the complex morphology (presence of columnar grains, columnar dendrites, equiaxed dendrites and cellular grains) in the weld zone. Moreover, scanning electron microscope images confirmed the presence of secondary phase in the weld zone and Energy Dispersive Spectroscopy found secondary phase rich in molybdenum (Mo). Potentiodynamic Polarization of weld zone showed excellent corrosion resistance properties in aggressive environment. The prime aim of the work is to understand the various aspects of the weld between two superior grades of different domain.