Investigation of metallurgical and mechanical properties of 21st century nickel-based superalloy 686 by electron beam welding technique

• Published in: Sadhana (Bangalore) Vol. 43; no. 8; pp. 1 - 10
• Main Authors: ARULMURUGAN, B, AGILAN, M, JEROME, S, ARIVARASU, M, MANIKANDAN, M, SRIKANTH, A, ARIVAZHAGAN, N
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.08.2018; Springer Nature B.V
• Subjects: Alloying elements; Base metal; Bend tests; Columnar structure; Corrosion rate; Corrosion resistance; Corrosion tests; Dendritic structure; Ductility; Ductility tests; Electron beam welding; Energy dispersive X ray spectroscopy; Engineering; Grain boundaries; Intermetallic phases; Interpolation; Mechanical properties; Metallurgical analysis; Nickel base alloys; Seawater; Superalloys; Tungsten; Weld strength; Welded joints; X-ray diffraction; electron beam welding; Alloy 686; microsegregation
• ISSN: 0256-2499; 0973-7677
• DOI: 10.1007/s12046-018-0850-x

Electron Beam Welding (EBW) was performed on the highly corrosion resistance superalloy 686. The present research work investigates the metallurgical and mechanical properties of the weld joint fabricated by Electron Beam Welding technique, and the results are compared with the base metal. Optical and Scanning Electron Microscope (SEM) analysis were carried out to study the structural properties of the weld joint. The fine equiaxed dendritic structure was revealed in the Center Fusion Zone (CFZ). The columnar dendrite was noticed in the Transition Fusion Zone (TFZ). Energy-dispersive X-ray spectroscopy (EDS) analysis results show that segregation of Mo and W were noticed in the sub-grain boundary. X-ray diffraction analysis (XRD) confirmed the presence of Mo and W rich phases in the weldment. Tensile testing was carried out to evaluate the strength and ductility of the weld joint. The result revealed that the weld strength was equal to the base metal strength. The presence of Mo and W-rich intermetallic phase reduced the ductility and toughness of the weld joint compared to base metal. Bend test confirmed the defect-free weld joint that was achieved in the Electron Beam Welding technique. The corrosion rate of base metal and EBW weldment are calculated in the synthetic seawater environment with the help of Potentiodynamic polarization experiment, and corrosion rate is measured with Tafel’s interpolation technique. The corrosion test result shows that the resistance of EBW weldment is lesser than base metal corrosion resistance because of the microsegregation of alloying elements in the interdendritic region.