Publication
Laser powder bed fusion of INCONELĀ® 718: optimization of process parameters and residual stress analysis before and after heat treatment
| dc.contributor.advisor | Silva, Francisco JosƩ Gomes da | |
| dc.contributor.author | Barros, Rafael de SĆ” | |
| dc.date.accessioned | 2020-03-27T17:18:16Z | |
| dc.date.available | 2020-03-27T17:18:16Z | |
| dc.date.issued | 2019 | |
| dc.description.abstract | Metals Additive Manufacturing (AM) is a āflourishingā technology, developing fast and successfully. Laser Powder Bed Fusion (LPBF) is among the most used metals AM processes in industry. InconelĀ® 718 (IN718) is a nickel-based superalloy that maintains its exceptional properties at high and low temperatures, thereby, it is a material commonly used to fabricate high performance components. The purpose of this work is to study the residual stress (RS) evolution of IN718 parts fabricated by LPBF, before and after heat treatment. Firstly, specimens with different combinations of parameters were fabricated to select the optimal LPBF process parameters. With the results from that part of the work, the influence of the individual process parameters on the porosity was studied. Then, new specimens were fabricated with the selected parameters and the RS analyzed by the hole-drilling strain-gage method, in as-built, solution annealed (SA) and SA plus double-aged (DA) conditions. It was concluded that increasing the scanning speed contributes to the reduction of the porosity. Also, for lower scanning speeds, 400 mm/s and lower, a hatching distance of 0.13 mm was defined as optimal. For higher scanning speeds, 600 and 800 mm/s, no relevant influence of the hatching distance, from 0.05 to 0.11 mm, on the porosity was observed. Laser power and layer thickness were not studied. Larger pores were found in specimens with higher porosity. Also, the specimens with higher porosity presented irregular pores and with lower porosity presented spherical-like pores. Regarding the RS evolution, as-built top surface presented uniform RS distribution of approximately 400 MPa. Lateral surface presented anisotropic distribution, with RS magnitudes of 600 to 800 MPa in build direction and 200 to 300 MPa horizontally. After the SA heat treatment, the RS decrease greatly to values between 50 ā 200 MPa. Series of carbides were found at the grain boundaries, which were attributed as the cause for oscillations in the RS profile. SA plus DA condition presented RS between 10 to 50 MPa. Heat-treated specimens revealed compressive RS at immediately near the surface. | pt_PT |
| dc.description.abstract | A fabricaĆ§Ć£o aditiva (FA) de metais Ć© uma tecnologia āflorescenteā, em rĆ”pido desenvolvimento e com sucesso. FusĆ£o a laser em leito de pĆ³ (LPBF) estĆ” entre os processos de FA de metais mais usados na indĆŗstria. InconelĀ® 718 Ć© uma superliga Ć base de Nickel, que mantĆ©m as suas propriedades excecionais a altas e baixas temperaturas, desse modo, Ć© comummente usada para produzir componentes de alto desempenho. O objetivo deste trabalho Ć© estudar a evoluĆ§Ć£o das tensƵes residuais (TR) de partes produzidas por LPBF, antes e pĆ³s tratamento tĆ©rmico. Primeiramente, produziram-se amostras com diferentes combinaƧƵes de parĆ¢metros do processo LPBF para selecionar os melhores parĆ¢metros. Com os resultados obtidos dessa parte do trabalho, foi estudada a influĆŖncia na porosidade dos diferentes parĆ¢metros. EntĆ£o, produziram-se novas amostras com os parĆ¢metros selecionados e foram analisadas as TR pelo mĆ©todo do furo cego incremental, nas condiƧƵes: āas-builtā, recozido (SA) e SA mais envelhecimento duplo (DA). Concluiu-se que o aumento da velocidade de varredura contribuĆ para a reduĆ§Ć£o da porosidade. TambĆ©m, para velocidades mais baixas, 400 mm/s e abaixo, a distĆ¢ncia entre passagens de 0.13 mm foi definida como Ć³tima. Para velocidades mais altas, 600 mm/s e 800 mm/s, a influĆŖncia da distĆ¢ncia entre passagens, de 0.05 a 0.11 mm, na porosidade Ć© desprezĆvel. A potĆŖncia do laser e a espessura das camadas nĆ£o foram estudados. Poros maiores foram observados nas amostras com maior porosidade. TambĆ©m, as amostras com maior porosidade exibiram poros irregulares, e com menor porosidade poros esfĆ©ricos. Em relaĆ§Ć£o Ć evoluĆ§Ć£o das TR, a face superior āas-builtā apresentou uma distribuiĆ§Ć£o das TR uniforme de aproximadamente 400 MPa. A face lateral apresentou distribuiĆ§Ć£o anisotrĆ³pica, com TR entre 600 e 800 MPa na direĆ§Ć£o de deposiĆ§Ć£o, e entre 200 e 300 MPa horizontalmente. Nas amostras SA, as TR reduziram substancialmente para valores entre 50 e 200 MPa. Foram detetados conjuntos de carbonetos, aos quais se atribuiu a ocorrĆŖncia de oscilaƧƵes no perfil das TR. A condiĆ§Ć£o SA mais DA apresentou TR entre 10 e 50 MPa. As amostras tratadas termicamente revelaram TR Ć compressĆ£o bem prĆ³ximo da superfĆcie. | pt_PT |
| dc.identifier.tid | 202343618 | pt_PT |
| dc.identifier.uri | http://hdl.handle.net/10400.22/15667 | |
| dc.language.iso | eng | pt_PT |
| dc.subject | Metals Additive Manufacturing | pt_PT |
| dc.subject | Laser Powder Bed Fusion | pt_PT |
| dc.subject | InconelĀ® 718 | pt_PT |
| dc.subject | Residual stresses | pt_PT |
| dc.subject | Hole-drilling strain-gage method | pt_PT |
| dc.subject | FabricaĆ§Ć£o aditiva de metais | pt_PT |
| dc.subject | FusĆ£o a laser em leito de pĆ³ | pt_PT |
| dc.subject | TensƵes residuais | pt_PT |
| dc.subject | MĆ©todo do furo cego incremental | pt_PT |
| dc.title | Laser powder bed fusion of INCONELĀ® 718: optimization of process parameters and residual stress analysis before and after heat treatment | pt_PT |
| dc.type | master thesis | |
| dspace.entity.type | Publication | |
| rcaap.rights | openAccess | pt_PT |
| rcaap.type | masterThesis | pt_PT |
| thesis.degree.name | Mestrado em Engenharia MecĆ¢nica - Materiais e Tecnologias de Fabrico | pt_PT |