Abstract: Wire Arc Additive Manufacturing (WAAM) has shown promising attributes in the aspects of higher material deposition rates, however is an inherently complex process to model and control due to relatively large amounts of global heat input as well as rapid solidification
rates . Microstructures in MIG style welding have been well characterized and are commonly known to show epitaxial, columnar and equiaxed morphologies . This paper outlines studies performed on a WAAM machine at the University of Idaho used to deposit Ni-200 wire onto
single crystal substrates using directional solidification principles to manipulate morphologies of deposited material during cooling to promote epitaxial single crystal grain growth. Initial studies were performed on cold rolled Ni-200 plate as well as a piece of zone refined nickel with
randomly oriented grains on the order of 5 mm in diameter, while further studies were performed on 99.995% pure single crystal nickel oriented in the (111) direction. Preliminary test results yielded a strong tendency for columnar grain growth epitaxially from the substrate when grain sizes were within roughly 100 µm, while further tests suggest planar growth with substrate grains in excess of 1 mm.
Authors: Jacob D. Miller and Michael Maughan
Keywords: Nickel, WAAM, Solidification