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Crack density and microhardness of Alloy 247LC manufactured by laser powder bed fusion
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
2021 (English)Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

Additive manufacturing (AM) enables the manufacturing of complex geometries,with beneficial mechanical properties in components used for aircraft and gas turbines applications. Alloy 247LC produced using laser powder bed fusion (L-PBF)is susceptible to cracking during the production process and must be post-processed using hot isostatic pressing (HIP), in addition to solution heat treatment (ST) and ageing heat treatmentsto heal cracks and attain the desired properties.The purpose of this study is to investigate L-PBF Alloy 247LC in both its as-built and as-built + heat-treated states(HIP and HIP + ST + ageing). Cracks, and microhardness were mainly studied. Sections cut in the built direction and transverse to the built direction were investigated in all the conditions i.e. in as-built and heat-treated states. The grains in the Z-Y direction are columnar and orientated in the build direction, while the grains in the X-Y plane are equiaxed. During the heat-treatments of the samples, substantial grain growth occurred indicating recrystallization. The cracks density appeared to be higher in the X-Y plane compared to the Z-Y plane. Cracks were absent after HIP. The microhardness appearedto be higher in the Z-Y plane compared to the X-Y plane in both low and high indentation load. This indicates anisotropy. In addition, low indentation load produced higher microhardness than a higher indentation load. This was observed in both the X-Y and Z-Y planes. It was also observed in the as-built and heat-treated conditions. HIP conditions had lower microhardness values than both the as-built and HIP + ST + Aged conditions. Microhardness values in the as-built is similar to those of the HIP + ST + Aged conditionswhich suggests that γ' does exist in the as-built state.

Place, publisher, year, edition, pages
2021. , p. 22
Keywords [en]
Alloy 247LC, L-PBF, AM, solution heat treatment, HIP
National Category
Manufacturing, Surface and Joining Technology
Identifiers
URN: urn:nbn:se:hv:diva-17756Local ID: EXP800OAI: oai:DiVA.org:hv-17756DiVA, id: diva2:1610968
Subject / course
Mechanical engineering
Educational program
Masterprogram i tillverkningsteknik
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Available from: 2021-12-06 Created: 2021-11-12 Last updated: 2021-12-06Bibliographically approved

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