Loading...
Publication
Otimização dos parâmetros de impressão 3D e caracterização da liga 1.2709 pelo processo de Selective Laser Melting
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 5.9 MB | Adobe PDF |
Authors
Abstract(s)
O fabrico aditivo de metais tem ganho uma grande relevância nas últimas duas décadas, pela capacidade de produzir peças complexas e otimizadas, com menor desperdício de material e elevada liberdade geométrica, que seriam difíceis ou até mesmo impossíveis de obter por processos convencionais. Entre as várias tecnologias existentes dentro do fabrico aditivo, o selective laser melting consolidou-se como uma das tecnologias mais promissoras, na medida
em que permite a produção de ligas de alto desempenho, como o aço maraging 1.2709, com elevada densidade e propriedades mecânicas competitivas. Esta tecnologia utiliza um feixe de laser de elevada potência para fundir camadas de pó metálico, previamente espalhadas sobre a plataforma de construção. Contudo, é reconhecido que pequenas variações nestes parâmetros podem ter impacto significativo no desempenho final do material, o que justifica a necessidade de trabalhos experimentais que explorem e otimizem estas condições. Apesar das
vantagens, o fabrico por selective laser melting (SLM) introduz desafios específicos. De referir a solidificação rápida e os gradientes térmicos elevados, que originam microestruturas com presença de austenite retida, porosidade e anisotropias dependentes da orientação de construção, bem como a rugosidade superficial elevada, característica intrínseca do processo que pode afetar negativamente o seu desempenho, nomeadamente em fadiga. Neste contexto,
a presente dissertação teve como objetivo estudar a influência dos parâmetros de impressão, nomeadamente a energia volumétrica e a estratégia de varrimento (chessboard e stripes), bem como do tratamento térmico de envelhecimento, nas propriedades finais do aço maraging 1.2709 produzido por SLM. Para tal, foram fabricados provetes cúbicos e de tração, que foram submetidos a ensaios de massa volúmica, rugosidade, dureza Vickers e tração, tanto no estado
como impresso como após envelhecimento. A metodologia seguiu normas internacionais de ensaio e recorreu a uma matriz experimental que permitiu avaliar de forma comparativa diferentes combinações de parâmetros de processo. Os resultados mostraram que energias elevadas conduzem a provetes densificados (99,5%) e com boas propriedades mecânicas, enquanto energias reduzidas originam porosidade elevada e degradação significativa do desempenho. A dureza aumentou de 350-380 HV no estado como impresso para 540-580 HV após envelhecimento, confirmando o endurecimento por precipitação. Nos ensaios de tração, registou-se um aumento da resistência última de 1014 MPa para 1923 MPa após envelhecimento, acompanhado de uma redução da deformação na rotura de 8% para 2%. Em conclusão, este estudo demonstrou que a combinação de parâmetros de fabrico adequados e tratamento de envelhecimento permite produzir aço maraging 1.2709 por SLM com propriedades equivalentes às obtidas por meios convencionais. Estes resultados reforçam o potencial desta tecnologia para aplicações estruturais de elevado desempenho e fornecem dados experimentais úteis para futuros trabalhos.
Additive manufacturing of metals has gained significant relevance over the last two decades due to its ability to produce complex and optimised parts with less material waste and high geometric freedom, which would be difficult or even impossible to achieve using conventional processes. Among the various technologies available within additive manufacturing, selective laser melting has established itself as one of the most promising technologies, as it allows the production of high-performance alloys, such as 1.2709 maraging steel, with high density and competitive mechanical properties. This technology uses a high-power laser beam to melt layers of metal powder, previously spread over the build platform. However, it is recognised that small variations in these parameters can have a significant impact on the final performance of the material, which justifies the need for experimental work to explore and optimise these conditions. Despite its advantages, selective laser melting (SLM) manufacturing introduces specific challenges. These include rapid solidification and high thermal gradients, which give rise to microstructures with retained austenite, porosity and anisotropies dependent on the build orientation, as well as high surface roughness, an intrinsic characteristic of the process that can negatively affect its performance, particularly in terms of fatigue. In this context, the aim of this dissertation was to study the influence of printing parameters, namely volumetric energy and scanning strategy (chessboard and stripes), as well as ageing heat treatment, on the final properties of 1.2709 maraging steel produced by SLM. To this end, cubic and tensile test specimens were manufactured and subjected to density, roughness, Vickers hardness and tensile tests, both in the as-printed state and after ageing. The methodology followed international testing standards and used an experimental matrix that allowed for the comparative evaluation of different combinations of process parameters. The results showed that high energies lead to densified specimens (99.5%) with good mechanical properties, while low energies result in high porosity and significant performance degradation. Hardness increased from 350-380 HV in the as-printed state to 540-580 HV after ageing, confirming precipitation hardening. In tensile tests, an increase in ultimate strength from 1014 MPa to 1923 MPa was recorded after ageing, accompanied by a reduction in deformation at break from 8% to 2%. In conclusion, this study demonstrated that the combination of appropriate manufacturing parameters and ageing treatment allows the production of 1.2709 maraging steel by SLM with properties equivalent to those obtained by conventional means. These results reinforce the potential of this technology for high-performance structural applications and provide useful experimental data for future work.
Additive manufacturing of metals has gained significant relevance over the last two decades due to its ability to produce complex and optimised parts with less material waste and high geometric freedom, which would be difficult or even impossible to achieve using conventional processes. Among the various technologies available within additive manufacturing, selective laser melting has established itself as one of the most promising technologies, as it allows the production of high-performance alloys, such as 1.2709 maraging steel, with high density and competitive mechanical properties. This technology uses a high-power laser beam to melt layers of metal powder, previously spread over the build platform. However, it is recognised that small variations in these parameters can have a significant impact on the final performance of the material, which justifies the need for experimental work to explore and optimise these conditions. Despite its advantages, selective laser melting (SLM) manufacturing introduces specific challenges. These include rapid solidification and high thermal gradients, which give rise to microstructures with retained austenite, porosity and anisotropies dependent on the build orientation, as well as high surface roughness, an intrinsic characteristic of the process that can negatively affect its performance, particularly in terms of fatigue. In this context, the aim of this dissertation was to study the influence of printing parameters, namely volumetric energy and scanning strategy (chessboard and stripes), as well as ageing heat treatment, on the final properties of 1.2709 maraging steel produced by SLM. To this end, cubic and tensile test specimens were manufactured and subjected to density, roughness, Vickers hardness and tensile tests, both in the as-printed state and after ageing. The methodology followed international testing standards and used an experimental matrix that allowed for the comparative evaluation of different combinations of process parameters. The results showed that high energies lead to densified specimens (99.5%) with good mechanical properties, while low energies result in high porosity and significant performance degradation. Hardness increased from 350-380 HV in the as-printed state to 540-580 HV after ageing, confirming precipitation hardening. In tensile tests, an increase in ultimate strength from 1014 MPa to 1923 MPa was recorded after ageing, accompanied by a reduction in deformation at break from 8% to 2%. In conclusion, this study demonstrated that the combination of appropriate manufacturing parameters and ageing treatment allows the production of 1.2709 maraging steel by SLM with properties equivalent to those obtained by conventional means. These results reinforce the potential of this technology for high-performance structural applications and provide useful experimental data for future work.
Description
Keywords
Metal additive manufacturing Selective laser melting Processing parameters Mechanical properties Heat treatment Process optimization Fabrico aditivo metálico Parâmetros de processamento Propriedades mecânicas Tratamento térmico Otimização do processo