Grain boundary misorientation effects on creep and cracking in Ni-based alloys

Was, Gary S.; Thaveeprungsriporn, Visit; Crawford, Douglas C.

doi:10.1007/s11837-998-0249-y

Cited by 79 publications

(42 citation statements)

References 39 publications

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“…Lehockey and Palumbo 7 have shown that a high fraction of special boundaries significantly enhances the resistance to creep of pure nickel at elevated temperatures. Other studies [10][11][12][13][14][15][16][17][18][19] have demonstrated significant improvements in a number of properties, including stress-corrosion cracking, fatigue, weldability, and creep, with an increase in the special boundary fraction. In terms of stress-corrosion cracking, Ni, Ni-16Cr-9Fe-xC, and Alloy 600 have shown significant improvements with increased fractions of special boundaries, 11,13,16,19 and these findings have been attributed to both the intrinsic corrosion resistance, and the resistance to solute segregation and precipitation exhibited by special boundaries.…”

Section: Methodsmentioning

confidence: 99%

“…In terms of creep resistance, it has also been shown that the presence of a high fraction of special boundaries decreases the creep rate of Ni, Ni-16Cr-Fe, Alloy 625, and Alloy 738. 7,10,15,17,18 In fact, pure Ni microstructures containing special grainboundary fractions in excess of 50% exhibit improvements of 15-fold and fivefold, respectively, in steadystate creep rate and primary creep strain. 7,15 The EBSD hardware and software used in this work were manufactured by EDAX-TSL, Inc. (Mahwah, NJ).…”

Section: Methodsmentioning

confidence: 99%

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The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

et al. 2008

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In situ scanning electron microscopy was performed during elevated-temperature (ഛ760°C) tensile-creep deformation of a face-centered-cubic cobalt-based Udimet 188 alloy to characterize the deformation evolution and, in particular, the grain boundary-cracking evolution. In situ electron backscatter diffraction observations combined with in situ secondary electron imaging indicated that general high-angle grain boundaries were more susceptible to cracking than low-angle grain boundaries and coincident site-lattice boundaries. The extent of general high-angle grain-boundary cracking increased with increasing creep time. Grain-boundary cracking was also observed throughout subsurface locations as observed for postdeformed samples. The electron backscattered diffraction orientation mapping performed during in situ tensile-creep deformation proved to be a powerful means for characterizing the surface deformation evolution and in particular for quantifying the types of grain boundaries that preferentially cracked.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

et al. 2008

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“…Adicionalmente, é conhecido que a difusividade nos contornos de grão depende das características do contorno de grão. Os contornos de grãos são classificados em duas categorias [4][5][6][7]: (i) contornos de alto ângulo (random grain boudaries), altos valores de Σ e (ii) contornos de baixo ângulos (special grain boundaries), que são caracterizados por baixos valores de Σ. Sendo Σ o valor inverso da densidade de sítios coincidentes da rede (coincident site lattice -CSL). Dados experimentais confirmam que contornos de grão com Σ<29 apresentam propriedades especiais, como por exemplo, baixa difusividade [8][9][10].…”

Section: Introductionunclassified

Oxidação Intergranular De Ligas De Níquel Em Altas Temperaturas Usando Ebsd

Trindade¹,

Krupp²

2017

Tecnologia Em Metalurgia Materiais E Mineração

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ResumoEm geral, ligas a base de níquel exibem uma tendência ao ataque de oxidação preferencialmente ao longo de contornos de grãos da liga durante exposição a atmosferas corrosivas em altas temperaturas. Isto é devido ao maior transporte dos elementos e fácil nucleação em contornos de grão. Ligas de Ni contém elementos com alta afinidade por oxigênio, como o Al e o Ti, os quais são geralmente os responsáveis pela oxidação intergranular. Estudos experimentais de oxidação das ligas de níquel Inconel  718 (UNS N07718) e Inconel  625 (UNS N06625) foram realizados à temperatura de 850 °C usando termogravimetria e microscopia eletrônica de varredura (MEV) em combinação com a técnica de EBSD (difração de elétrons retroespalhados). O efeito da difusão do oxigênio e Cr ao longo de contornos de grãos das ligas foi analisado através da técnica de EBSD. Os resultados suportam a hipótese de que contornos de grãos de elevada fração de sítios de rede coincidentes -CSL (baixos valores de Σ) parecem exibir uma maior resistência ao ataque intergranular quando comparado com contornos de grãos de altos ângulos. Palavra-chave: Oxidação intergranular; Ligas à base de Ni; Técnica EBSD; Contornos de grãos de baixo ângulo; Difusão em contornos de grão. HIGH-TEMPERATURE INTERGRANULAR OXIDATION OF NI-BASED ALLOYS USING EBSD AbstractIn general, nickel-base alloys exhibit a tendency to preferred oxidation attack along the alloy grain boundaries during exposure to corrosive atmospheres at high temperatures. This is due to the much faster intergranular transport of the reacting elements in combination with easy nucleation of precipitates. Ni-base superalloys contain elements with a very high oxygen affinity, e.g., Al and Ti, which are often responsible for pronounced intergranular oxidation. Experimental studies on the oxidation behaviour of Ni-base superalloys Inconel  718 (UNS N07718) and Inconel  625 (UNS N06625) were carried out at temperature of 850 °C using thermogravimetry and analytical scanning electron microscopy in combination with EBSD (electron back-scattered diffraction). The effect of oxygen and Cr grain boundary diffusion on the overall oxidation process was analyzed by means EBSD technique. The results supported the assumption that special grain boundaries with a high fraction of coincident lattice sites (low Σ values) seems to exhibit a higher resistance to intergranular attack as compared to random high-angle grain boundaries. Keywords: Intergranular oxidation; Ni-based alloys; EBSD technique; Special grain boundaries; Grain boundary diffusion. INTRODUÇÃOAdição de cromo e alumínio é largamente usada como elementos capazes de proteger o metal base das ligas contra ataques corrosivos em altas temperaturas, através da formação de uma camada externa protetora composta de Cr 2 O 3 ou Al 2 O 3 [1,2]. Uma subcamada de SiO 2 , mesmo que parcial sob camadas de Cr 2 O 3 tem mostrado muito eficiente na proteção contra corrosão em altas temperaturas [2]. No entanto, mesmo com a presença de tais camadas óxidas, corrosão interna (oxi...

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“…Since that time, such manipulations have become known as grain boundary engineering. Grain boundary engineering has been demonstrated to be a viable means of improving certain properties of low to medium stacking fault energy FCC materials such as austenitic stainless and microalloyed steels [2,3], nickel and nickel-based alloys [2,[4][5][6][7][8][9][10][11][12][13][14][15], and lead alloys [16][17][18]. The susceptible properties are typically grain boundary controlled, such as corrosion and stress corrosion cracking [2,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], creep and cavitation [19][20][21][22], and weldability [23].…”

Section: Introductionmentioning

confidence: 99%

“…An additional benefit of the strain annealing lies in the "fine-tuning" of the misorientations to smaller deviations from the exact CSL description. Multiple, or repeated strain annealing treatments on ultrahigh-purity Ni-16Cr-9Fe were performed by Was et al [15] to improve creep and cracking resistance. The improvement in the GBCD resulted from a two or three step deformation and annealing treatment.…”

Section: Introductionmentioning

confidence: 99%

Influence of Processing Method on the Grain Boundary Character Distribution and Network Connectivity

1999

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There exists a growing body of literature that correlates the fraction of "special" boundaries in a microstructure, as described by the Coincident Site Lattice Model, to properties such as corrosion resistance, intergranular stress corrosion cracking, creep, etc. Several studies suggest that the grain boundary character distribution (GBCD), which is defined in terms of the relative fractions of "special" and "random" grain boundaries, can be manipulated through thermomechanical processing. This investigation evaluates the influence of specific thermomechanical processing methods on the resulting GBCD in FCC materials such as oxygenfree electronic (ofe) copper and Inconel 600. We also demonstrate that the primary effect of thermomechanical processing is to reduce or break the connectivity of the random grain boundary network. Samples of ofe Cu were subjected to a minimum of three different deformation paths to evaluate the influence of deformation path on the resulting GBCD. These include: rolling to 82% reduction in thickness, compression to 82% strain, repeated compression to 20% strain followed by annealing. In addition, the influence of annealing temperature was probed by applying, for each of the processes, three different annealing temperatures of 400, 560, and 800°C. The observations obtained from automated electron backscatter diffraction (EBSD) characterization of the microstructure are discussed in terms of deformation path, annealing temperature, and processing method. Results are compared to previous reports on strainannealed ofe Cu and sequential processed Inconel 600. These results demonstrate that among the processes considered, sequential processing is the most effective method to disrupt the random grain boundary network and improve the GBCD.

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Grain boundary misorientation effects on creep and cracking in Ni-based alloys

Cited by 79 publications

References 39 publications

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

Oxidação Intergranular De Ligas De Níquel Em Altas Temperaturas Usando Ebsd

Influence of Processing Method on the Grain Boundary Character Distribution and Network Connectivity

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