Microstructure and tensile properties of microwave welded hastelloy c-276 joints

Abstract

In this paper, microwave joining of Hastelloy C-276 joints is reported using Hastelloy C-276 powder as an interlayer (~ 15 ± 6 µm). Microwave hybrid heating technique was adopted to develop the joints using a graphite susceptor inside a multimode microwave applicator at 900 W power, frequency of 2.45 GHz and 760 s exposure time. The joints were characterized to study the microstructure, hardness, and tensile properties. Microstructural analysis revealed defect and crack-free joints with adequate metallurgical bonding and diffusion between interface layer and base material. Fine cellular (spherical) microstructure and skeleton-like hard carbides were present at the grain boundaries. Formation of intermetallic phases Fe3Ni and Ni3Cr was confirmed by the XRD analysis, whereas hard carbides Mo2C and W2C were identified by EDS analysis. The welded zone possesses 23% higher microhardness than base metal with an average microhardness of 282 HV. The ultimate tensile strength of the joint was estimated 602 ± 22 MPa with 20% of elongation capacity, and the achieved joint efficiency was 82%. Fractography analysis reveals the failure of the joint due to mixed (shear, ductile, and brittle) modes.