Influence of Heat Input on Grain Structure in Thin-Wall Deposits using Laser Metal Powder Deposition
2016 (English)In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, -7 p.Conference paper (Refereed)
Laser metal deposition (LMD) is an additive manufacturing method which is used to deposit material directly onto a metal surface layer upon layer until a final component is achieved. The material used in this study is the nickel iron based superalloy Alloy 718. There is a strong thermal gradient associated with this method which generally produces columnar grains growing in the build-up direction. The preferred solidification orientation of the FCC matrix is in the (001) direction which makes it possible to build directionally solidified structures with epitaxial grains growing through the layers. In this study LMD with powder as additive has been used to build thin walled samples, multiple layers high. The main objectives of this research are to assess the influence of the heat input on the grain structure in LMD builds and evaluate how the morphology and texture of the grains are affected by the changes in process parameters. Two different parameter sets are compared where a high and a low heat input have been used. The two samples with different heat inputs have been evaluated using a scanning electron microscope coupled to an electron back scatter diffraction detector in order to obtain quantitative grains size measurements as well as crystallographic information. It was shown that the grain structure was considerably affected by the heat input where the high heat input produced a strong texture with columnar grains growing in the build-up direction. With a low heat input the grains became finer and, although elongated, the grains became more equiaxed.
Place, publisher, year, edition, pages
Lund: Swedish Production Academy , 2016. -7 p.
Laser metal deposition, additive manufacturing, crystallography, iron-nickel superalloy
Manufacturing, Surface and Joining Technology
IdentifiersURN: urn:nbn:se:hv:diva-10248OAI: oai:DiVA.org:hv-10248DiVA: diva2:1053124
7th International Swedish Production Symposium, SPS16, Lund, Sweden, October 25–27, 2016