TECHNICAL PAPER Effect of Power Input on Metallurgical and Mechanical Characteristics of Inconel-625 Welded Joints Processed Through Microwave Hybrid Heating Ravindra I. Badiger 1 • S. Narendranath 1 • M. S. Srinath 2 • Ajit M. Hebbale 3 Received: 17 August 2018 / Accepted: 5 December 2018 Ó The Indian Institute of Metals - IIM 2019 Abstract In the present study, welding of Inconel-625 through the use of microwave hybrid heating (MHH) has been achieved at two power levels 600 W and 900 W in a low-cost home microwave oven. Nickel-based powder EWAC was used as filler interface between faying sur- faces. Effect of power variation on the metallurgical and mechanical characteristics of the microwave welded joints has been investigated. Developed joints were characterized through XRD, optical microscope, SEM, universal testing machine and Vickers microhardness tester. XRD study of the weld zone indicated the formation of various carbides and intermetallics. Joint microstructures witnessed a com- pletely fused weld interface without any interfacial cracks. EDS analysis of the joint microstructure revealed lesser amount of segregation of niobium and molybdenum with the specimens developed at 600 W which could be attrib- uted to the lower heat input associated with 600 W power that also resulted in fine grain structure. Further, the specimens processed at 600 W exhibited better tensile and flexural properties when compared to their counterparts produced at 900 W power. Fractography study of the specimens revealed a combined ductile and brittle fracture. Keywords Inconel-625 Á Microwave hybrid heating Á EWAC Á Tensile strength Á Flexural strength 1 Introduction Inconel-625 finds widespread use in aeronautical, marine and nuclear industries due to its high strength, excellent fabricability and exceptional corrosion resistance. The alloy is solid solution strengthened by the addition of niobium and molybdenum in its nickel–chromium matrix. The construction and repair of Inconel-625 components generally used in chemical power plants and power gen- erators are commonly carried out using conventional welding techniques such as gas tungsten arc welding (GTAW), laser welding and electron beam welding. [1, 2]. One of the key concerns during welding of nickel-based alloys is the formation of a brittle intermetallic compound known as Laves phase. Formation of Laves phase occurs by consumption of useful elements such as niobium and molybdenum from the alloy and segregation in the inter- granular regions. Further, the Laves phase promotes hot cracking, thereby deteriorating the mechanical properties of welded joints [3, 4]. Reports from the past [5–7] revealed that a slight variation in composition of Nb, Si and C strongly influences the type and amount of secondary phases that are formed during the termination of solidifi- cation process. Several researchers have reported on weldability of nickel-based alloys through GTAW using different filler metals. It has been observed that the quality of the dis- similar joints obtained depends upon proper selection of filler wire which otherwise will lead to solidification cracking, heat-affected zone liquation cracking and for- mation of Laves phase. Patterson and Milewski [8] inves- tigated welding of dissimilar alloys Inconel-625 and SS- 304L using pulsed current GTA process. Hot cracked surfaces rich in S, Nb, P and C were found in the weld- ments along with secondary eutectic phases in the & Ravindra I. Badiger rbadiger74@gmail.com 1 Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, Karnataka, India 2 Department of Industrial and Production Engineering, Malnad College of Engineering, Hassan, Karnataka, India 3 Department of Mechanical Engineering, NMAM Institute of Technology, Nitte, Karnataka, India 123 Trans Indian Inst Met https://doi.org/10.1007/s12666-018-1537-z