Additive Manufacturing of CoCrFeMnNi High-Entropy Alloy/AISI 316L Stainless Steel Bimetallic Structures Rathinavelu Sokkalingam, Zhao Chao, Katakam Sivaprasad, Veerappan Muthupandi, Jayamani Jayaraj, et al. Advanced Engineering Materials, 2023 CoCrFeMnNi high‐entropy alloy (HEA)/AISI 316L stainless steel bimetals were additively fabricated using selective laser melting (SLM). The bimetal structure comprises three regions, i.e., CoCrFeMnNi‐HEA, AISI 316L stainless steel, and an interface between CoCrFeMnNi‐HEA, AISI 316L stainless steel. SLM processing results in the formation of columnar grains extending over many built layers epitaxially in a preferential <100> growth direction. The Vickers microhardness ranges mainly between 250 and 275 HV0.5 in all three observed regions. In addition, only a marginal variation in tensile strength is observed between the CoCrFeMnNi‐HEA, AISI 316L stainless steel, and the CoCrFeMnNi‐HEA/AISI 316L stainless steel bimetal. The unique higher work hardening behavior of the CoCrFeMnNi‐HEA prevents failure along the CoCrFeMnNi‐HEA side in the bimetallic structure during plastic deformation. The CoCrFeMnNi‐HEA shows higher pitting susceptibility than the AISI 316L stainless steel in the bimetallic structure due to its lower pitting potential. Further, the presence of pores and lack of fusion spots further decreases the pitting resistance of the CoCrFeMnNi‐HEA. Hence, the bimetal is prone to more preferential corrosion attack along the CoCrFeMnNi‐HEA side due to its anodic behavior and defects.
Dissimilar welding of high-entropy alloy to Inconel 718 superalloy for structural applications R. Sokkalingam, B. Pravallika, K. Sivaprasad, V. Muthupandi, K. G. Prashanth Journal of Materials Research, 2022 High-entropy alloy, a new generation material, exhibits superior structural properties. For high-temperature applications, where dissimilar materials are in demand, HEAs may be joined with commercially available structural materials to improve their performance-life ratio. In this connection, a dissimilar joint was fabricated by gas tungsten arc welding between Al0.1CoCrFeNi-HEA and Inconel 718. The columnar dendritic grains are growing epitaxially at the Al0.1CoCrFeNi-HEA/weld metal interface, where their compositions are matching. While the composition misfit at the weld metal/Inconel 718 interface, reveals the non-epitaxial mode of solidification. In addition, the fusion zone exhibits the porosity and micro-segregation of NbC and Laves phases. The joint shows a joint efficiency of ~ 88%, where the strength is observed to be 644 MPa with 21% ductility. The results demonstrate the applicability of GTAW in fabricating the dissimilar weld joints between HEA and Inconel 718 for structural applications. Graphic abstract
Microstructure and properties of in-situ high entropy alloy/tungsten carbide composites by mechanical alloying. Rathinavelu Sokkalingam, Marek Tarraste, Kumar Babu Surreddi, Rainer Traksmaa, Veerappan Muthupandi, et al. Material Design and Processing Communications, 2021 Al0.1CoCrFeNi-high entropy alloy (HEA) /tungsten carbide (WC)metal matrix composite was successfully prepared by mechanical alloying and subsequent spark plasma sintering. The different vo ...
Electron-beam welding of high-entropy alloy and stainless steel: microstructure and mechanical properties R. Sokkalingam, P. Mastanaiah, V. Muthupandi, K. Sivaprasad, K. G. Prashanth Materials and Manufacturing Processes, 2020 An autogenously dissimilar Al0.1CoCrFeNi-high entropy alloy/stainless steel (i.e., AISI 304) weld joint was produced by an electron-beam welding technique. The weld metal followed mode A of solidification and resulted in a fully austenitic columnar dendritic microstructure due to rapid cooling and lower chromium equivalent to nickel equivalent (Creq/Nieq) ratio (1.12–1.14). Tensile test sample fractures at the base metal (Al0.1CoCrFeNi-high entropy alloy) and illustrates higher strength (the yield and ultimate strength of 310 ± 10 MPa and 560 ± 15 MPa, respectively) than that of Al0.1CoCrFeNi-high entropy alloy, ensuring the suitability of the electron-beam welding for the Al0.1CoCrFeNi-high entropy alloy/AISI 304 stainless steel joint structures designed with respect to Al0.1CoCrFeNi-HEA properties. The influence of the manufacturing process (electron beam welding) is highlighted in terms of microstructure and mechanical properties.
