Comprehensive study on the formation of grain boundary serrations in additively manufactured Haynes 230 alloy

Document identifier: oai:DiVA.org:ltu-77902
Access full text here:10.1016/j.matchar.2019.110092
Keyword: Engineering and Technology, Materials Engineering, Manufacturing, Surface and Joining Technology, Teknik och teknologier, Materialteknik, Bearbetnings-, yt- och fogningsteknik, Additive manufacturing, Laser metal deposition, Grain boundary serration, Superalloy, Haynes 230, EBSD, Produktionsutveckling, Manufacturing Systems Engineering
Publication year: 2020
Abstract:

Recently, grain boundary serrations have been introduced in conventionally processed Haynes 230 through a slow-cooling heat treatment. The aim of this work was to utilize these heat treatments to introduce serrations in additively manufactured (Laser Metal Deposition) Haynes 230. Contrary to expectations, serrations already formed during the fast-cooling of the Laser Metal Deposition process. Electron Backscatter Diffraction was used to elucidate the underlying phenomenon for the emergence of serrations during fast-cooling. As a result, a hypothesis regarding a new mechanism responsible for the formation of grain boundary serrations was formulated. Additionally, specific characteristics of the Laser Metal Deposition process have been identified. This includes a columnar-to-equiaxed transition (CET) for slower feed rates, leading to smaller grains despite lower cooling rates; the observation of an abrupt increase in grain growth for a raised solution annealing temperature; the fact that serrations hinder uncontrolled grain growth and finally that the LMD-process leads to a finer carbide morphology compared to conventional manufacturing methods, potentially leading to an increased precipitation strengthening effect.

Authors

Maximilian Haack

Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
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Martin Kuczyk

Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
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André Seidel

Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
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Elena López

Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
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Frank Brueckner

Luleå tekniska universitet; Produkt- och produktionsutveckling; Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
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Christoph Leyens

Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Dresden University of Technology, Institute of Materials Science, Dresden, Germany
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