Preliminary Metallurgical and Mechanical Investigations of Microwave Processed Hastelloy Joints

Abstract

In this paper, joining of Hastelloy has been successfully carried out by microwave hybrid heating process. The joints were developed by using a microwave oven at a frequency of 2.45 GHz and 900 W. A thin layer of slurry consisting of nickel-based powder and epoxy resin was introduced between the faying surfaces. The joints obtained by microwave hybrid heating were characterized by XRD, SEM–EDS, Vicker's microhardness, and tensile tests. Microstructure analysis revealed the formation of equiaxed grains, and results of XRD analysis revealed formation of some intermetallics and suppression of carbide formation. This can be attributed to the volumetric heating nature of microwaves. The microhardness study revealed 320 ± 25 HV hardness on grain surfaces and 680 ± 40 HV on grain boundaries. The tensile strength of the microwave processed joints was∼82% of base Hastelloy strength. The fractographic analysis of the fractured samples revealed a ductile fracture coupled with the shearing of brittle carbides in the joint region. An overall study revealed the potential of microwaves in joining of bulk metallic materials.