Effect of carbon content on the microstructure and creep properties of a 3rd generation single crystal nickel-base superalloy

Li, X.W.; Liu, Tianshu; Wang, L.; Liu, X.G.; Lou, Langhong; Zhang, J.

doi:10.1016/j.msea.2015.05.039

Cited by 19 publications

(13 citation statements)

References 35 publications

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“…Due to the complicated alloy composition and usage of heavy elements such as W, Mo and Ta, the material inevitably contains defects such as shrinkage pores inherited from the solidification process [1,[4][5][6]. Also, due to the addition of carbon to improve the castability, carbides are common features, located at the interdendritic regions [7][8][9]. These shrinkage pores and carbides are usually associated with fatigue crack initiation under service conditions and can influence fatigue crack propagation depending on the size of the pores and carbides, applied strain amplitude, test temperature and environment [4,[10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Strain accumulation and fatigue crack initiation at pores and carbides in a SX superalloy at room temperature

Jiang

Bull

Evangelou

et al. 2018

International Journal of Fatigue

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Pores and carbides inherited from SX superalloy manufacturing processes usually act as stress concentrators and are preferential sites for fatigue crack initiation. In this study, pore & carbide size, morphology and distribution in a SX superalloy MD2 has been evaluated by X-ray CT. Strain accumulation and fatigue cracking behaviour in MD2, particularly around the pores and carbides, has been investigated by ex-situ SEM-DIC at room temperature along with image-based modelling of the observed MD2 defect populations obtained through X-ray CT imaging. The deformation structures have also been examined by electron channelling contrast imaging under controlled diffraction conditions. The results indicate that the pores & carbides with complicated three-dimensional features are the dominant fatigue crack initiation sites. Deformation is concentrated within intense slip bands and an enhanced strain accumulation around pores is captured by SEM-DIC. Dislocation motion is mainly confined to the γ matrix channels with some dislocation shear cutting of γʹ precipitates also observed ahead of the crack tip. As the crack propagates, strain band density and dislocation density at the crack tip increases correspondingly. Image-based modelling using the observed defect populations in MD2 (micro)structure can effectively predict the stress concentrations and the resultant hot spot for subsequent fatigue crack initiation, which is consistent with the experimental observations.

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Section: Introductionmentioning

confidence: 99%

Strain accumulation and fatigue crack initiation at pores and carbides in a SX superalloy at room temperature

Jiang

Bull

Evangelou

et al. 2018

International Journal of Fatigue

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“…The distributions were obtained by a point matrix scanning technique. This method was often used to characterize segregation [ 9,20,21 ] for the following advantages. First, the contents of all points can show the distribution of elements when the dendritic structures vanished after SHT.…”

Section: Resultsmentioning

confidence: 99%

“…Instead of extruding pores by HIP, the way prolonging solution time reduces porosity by homogenization. According to the literature, [ 20,21,33 ] the porosity and segregation clearly negative relate to the creep life. After the maximum point (HT2 here), both porosity and segregation decrease, as the time increase during SHT.…”

Section: Resultsmentioning

confidence: 99%

“…Adjusting the minor elements [ 18,19 ] was used to reduce S‐pores, but the similar methods have little effect on H‐pores. [ 16,20 ] Many investment [ 10 ] indicated that refining the dendritic structures by increasing the withdraw rate during directional solidification reduces S‐pores, but few of them mentioned the variation of these S‐pores after SHT. Hot isostatic pressing (HIP) seems to be the only effective way to eliminate H‐pore.…”

Section: Introductionmentioning

confidence: 99%

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Variation of Homogenization Pores during Homogenization for Nickel‐Based Single‐Crystal Superalloys

et al. 2021

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The porosity deteriorates the mechanical properties of nickel‐based superalloys, especially the fatigue properties. Herein, the kinetics model of homogenization porosity growth is optimized. The corresponding diffusion processes during solution heat treatment are simulated by the DICTRA software and verified by experiments. The results show that the homogenization porosity increases first and then decreases during the solution heat treatment, due to the imbalanced diffusion flux between dendritic core (DC) and interdendritic areas (IAs). The diffusion flux first flows toward DC and then toward IAs after fully homogenization of the fast diffusion elements. Moreover, the influence of directional solidification parameters on the homogenization porosity process is investigated. With the increase in the withdraw rate, the dendritic structure is refined, and the S‐porosity decreases. Meanwhile, the dendritic arm spacing decreases; thus, homogenization accelerated increases. In this case, after the solution heat treatment, the homogenization porosity decreases. The results provide two bases to propose a new method to control the homogenization porosity.

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“…Consequently, the carburized layer disappeared after 1000 h, and the content of carbon was reduced in the HY5 coating detected by EDS, which indicated that the inhibition of elements diffusion reduced at the same time. This showed that carbon cannot completely hinder interdiffusion but could slow down the inward aluminium diffusion and the outward substrate elements diffusion [ 34 , 35 ].…”

Section: Resultsmentioning

confidence: 99%

The Interdiffusion Behavior of NiCoCrAlYHf Coating Deposited by Arc Ion Plating on Carburized Ni-Based Single Crystal Superalloy

et al. 2021

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In the present study, arc ion plating (AIP) was used to prepare a NiCoCrAlYHf coating (HY5 coating) on a carburized third-generation single-crystal superalloy DD10. The interdiffusion behavior of the carburized superalloy with an HY5 coating was investigated for a 1000 h oxidation time at 1100 °C. Carburization enhanced the interfacial bonding force and improved the microstructure of the NiCoCrAlYHf coating. An interdiffusion zone (IDZ) formed after a 300 h oxidation time, and the formation of a carburized layer effectively suppressed an inward diffusion of cobalt, aluminium, and chromium to the DD10 superalloy as well as an outward diffusion of nickel and refractory elements for instance rhenium and tungsten to the HY5 coating that occurred in static air at 1100 °C. The roles of the carburized layer in affecting thermal cyclic oxidation and element interdiffusion were studied. Subsequently, a modified form of the Boltzmann–Matano analysis was used to present the interdiffusion coefficients of aluminium.

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Effect of carbon content on the microstructure and creep properties of a 3rd generation single crystal nickel-base superalloy

Cited by 19 publications

References 35 publications

Strain accumulation and fatigue crack initiation at pores and carbides in a SX superalloy at room temperature

Strain accumulation and fatigue crack initiation at pores and carbides in a SX superalloy at room temperature

Variation of Homogenization Pores during Homogenization for Nickel‐Based Single‐Crystal Superalloys

The Interdiffusion Behavior of NiCoCrAlYHf Coating Deposited by Arc Ion Plating on Carburized Ni-Based Single Crystal Superalloy

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