Effect of Cooling Rate on Microstructural Development in Alloy 718

Patel, Ashish; Murty, Y. V.

doi:10.7449/2001/superalloys_2001_123_132

Cited by 15 publications

(8 citation statements)

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“…'Fan-like' microstructures similar to those observed in the top region of the deposit were reported by Antonsson et al [41], that narrated the effect of cooling rates and solidification structures formed of Alloy 718 by Levitation Casting (LC) technique having an undercooling of 40 • C at the highest growth temperature of 1300 • C, leading to an estimated cooling rate of 15,000 • C/s. Dendrites formed in the top region of DED deposits considered in this study are well-developed compared to the LC technique, indicating lower undercooling and relatively low cooling rates of 100-600 • C/s [27,42].…”

Section: Grain Morphologymentioning

confidence: 83%

Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718

Sreekanth

Ghassemali

Hurtig

et al. 2020

Metals

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The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation.

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Section: Grain Morphologymentioning

confidence: 83%

Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718

Sreekanth

Ghassemali

Hurtig

et al. 2020

Metals

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“…The inclination of Re concentration is higher for 100 K/min in comparison with 1 K/min, especially in the adjacent area to the dendrite boundary. According to A. D. Patel and Y. V. Murty, 11) and Wanhong Yang et al, 12) at lower cooling rates, there is enough time for back diffusion in the solid (solidification time is greater than diffusion time); hence, a lower fraction of eutectic laves (Ni 2 Nb) phase. This suggests that in large ingots, the volume fraction of laves phase is the highest at the surface of ingot and decreases towards the center part.…”

Section: Effect Of Re On Solidification Of St-in718 Alloymentioning

confidence: 99%

Influence of Rhenium and Cooling Rate on the Solidification of Ni Base Superalloys, Inconel 718

et al. 2005

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Influence of 2-6% Re additions has been investigated on the solidification phenomenon of a Ni base superalloy, In718. The solidification of each alloy proceeds in the order of primary , eutectic (+NbC) and eutectic (+Ni 2 Nb). Higher additions of Re increase the volume fraction of primary and enlarge the secondary dendrite arm spacing. The influence of cooling rates at 1, 10 and 100 K/min has also been studied on the solidification process of the alloy containing 3.5% Re. With increasing cooling rate, the crystallization start temperatures of primary and eutectic phases decrease and the volume fraction of NbC and Ni 2 Nb increase. EPMA analysis revealed that the distribution of alloy elements in microstructure also changed depending on cooling rate. The redistribution of alloy elements during solidification was evaluated by Clyne-Kurz and Ohnaka theories.

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“…Apesar da energia de soldagem modificar a diluição, o efeito sobre o refino da microestrutura deve estar ligado à alteração na taxa de resfriamento; quanto menor a energia de soldagem, maior a taxa de resfriamento e mais refinada fica a microestrutura. Esta hipótese está em concordância com estudos realizados por Antonsson e Fredriksson [15] e Patel e Murty [16] em lingotes de Inconel 718 (liga similar ao Inconel 625).…”

Section: Microestruturaunclassified

Efeito da energia de soldagem sobre a microestrutura e resistência à corrosão de revestimentos de Inconel 625 aplicados pelo processo GMAW

et al. 2020

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RESUMO A liga de Inconel 625 é uma superliga à base de níquel altamente resistente à corrosão particularmente utilizada na forme de revestimentos sobre um substrato menos nobre. Existem inúmeras formas de aplicação deste material, sendo uma delas o uso de processos de soldagem. Tradicionalmente faz-se uso de processos de deposição por soldagem que promovam baixa diluição (menor contaminação do Inconel com o material do substrato), mas estes processos possuem característica de baixa produtividade devido às baixas taxas de deposição empregadas. Assim, este estudo tem como objetivo avaliar a aplicação de Inconel 625 utilizando o processo GMAW com diferentes energias de soldagem, que possibilita operar com altas taxas de deposição, mas com o inconveniente de promover alta diluição. Para isso, revestimentos foram depositados com três níveis de energias de soldagem, avaliando seus efeitos sobre a microestrutura e a resistência à corrosão dos depósitos. As macros e microestruturas dos depósitos foram avaliadas por microscopia óptica, microscopia eletrônica de varredura (MEV), espectrometria de energia dispersa (EDS) e difração de raios-X (DRX). Foram medidas a diluição, os espaçamentos dendríticos secundários e avaliadas as microestruturas. A resistência à corrosão dos depósitos foi avaliada por ensaios de polarização potenciodinâmica cíclica. Os resultados mostraram que a relação entre energia de soldagem e diluição dependem da amplitude de tecimento. Observou-se também que a energia de soldagem afetou a quantidade de fases, sendo que energias mais baixas produziram estruturas dendríticas mais refinadas. Além disso, o estudo mostrou que os ensaios de corrosão realizados a temperatura de 25 ºC não promoveram corrosão superficial nas amostras independente da energia de soldagem imposta ao revestimento e que os ensaios a 60 º C causaram corrosão em todas as condições.

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Effect of Cooling Rate on Microstructural Development in Alloy 718

Cited by 15 publications

References 1 publication

Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718

Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718

Influence of Rhenium and Cooling Rate on the Solidification of Ni Base Superalloys, Inconel 718

Efeito da energia de soldagem sobre a microestrutura e resistência à corrosão de revestimentos de Inconel 625 aplicados pelo processo GMAW

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