Heat treatment effects on Inconel 625 components fabricated by wire + arc additive manufacturing (WAAM)—part 1: microstructural characterization

• Published in: International journal of advanced manufacturing technology Vol. 103; no. 9-12; pp. 3785 - 3798
• Main Authors: Tanvir, A. N. M., Ahsan, Md. R. U., Ji, Changwook, Hawkins, Wayne, Bates, Brian, Kim, Duck Bong
• Format: Journal Article
• Language: English
• Published: London Springer London 01-08-2019; Springer Nature B.V
• Subjects: Additive manufacturing; Arc heating; Arc welding; CAE) and Design; Computer-Aided Engineering (CAD; Electric arc melting; Engineering; Heat treating; Heat treatment; Industrial and Production Engineering; Laves phase; Mechanical Engineering; Media Management; Metal carbides; Microstructure; Morphology; Nickel base alloys; Original Article; Phase transitions; Superalloys; Wire; Heat treatment; Inconel 625; Cold metal transfer (CMT); Metal additive manufacturing; Wire + arc additive manufacturing (WAAM)
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-019-03828-6

Wire + arc additive manufacturing (WAAM) is a versatile, low-cost, energy-efficient technology used in metal additive manufacturing. This WAAM process uses arc welding to melt a wire and form a three-dimensional (3D) object using a layer-by-layer stacking mechanism. In the present study, a Ni-based superalloy wire, i.e., Inconel 625, is melted and deposited additively through a cold metal transfer (CMT)-based WAAM process. The deposited specimens were heat-treated at 980 °C (the recommended temperature for stress-relief annealing) for 30, 60, and 120 min and then water quenched to investigate the effect of heat treatment on microstructure and phase transformation and to identify the optimum heat treatment condition. Microstructural results show that the heat treatment, in general, eliminates the brittle Laves phases regardless of the time without changing the grain morphology. However, an increment in the amount of the delta phase is observed with the longer heat treatment periods. Additionally, the size of MC (metal carbide) of Nb is also observed to increase with heat treatment time. This study provides an in-depth understanding of the correlation between heat treatment time and microstructure in additively manufactured Inconel 625, which can facilitate determining the optimum heat treatment condition in a later study.