Fracture behavior of superalloy IN738LC with various precipitate microstructures

Balikci, Ercan; Mirshams, Reza A.; Raman, A.

doi:10.1016/s0921-5093(99)00012-x

Cited by 40 publications

(24 citation statements)

References 14 publications

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“…While a unimodal size distribution is represented by a single Gaussian, a multimodal size precipitate microstructure is composed of distinctly different precipitate size distributions and represented by more than one Gaussian. It has been previously reported [17,18] that the c¢ precipitates grow in a unimodal cuboidal morphology up to a critical size, beyond which a bimodal size distribution sets in, where visibly large and small size precipitates coexist. Trimodal precipitate microstructures with large, medium, and small particle sizes have also been reported.…”

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confidence: 89%

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Multimodal Precipitation in the Superalloy IN738LC

Balikci

Erdeniz

2010

Metall Mater Trans A

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ERCAN BALIKCI and DINC ERDENIZIN738LC is a polycrystalline, nickel-base superalloy, which is used in aggressive environments at high temperatures. The required strength is provided by precipitate strengthening. Both unimodal and multimodal precipitate distributions are observed in IN738LC. After reaching a critical size, a unimodal precipitate microstructure transforms to a bimodal one. This transformation is controlled by the precipitate-matrix interface, which is under compression in IN738LC. As the unimodal precipitates grow, the strained interface, due to differential lattice parameter of the matrix and the precipitate phase, stops solute diffusion into the growing precipitates. Hence, the solute atoms, entrapped in the matrix, saturate the matrix and form new, fine precipitates. Dissolution of some large precipitates also supplies solute to supersaturate the matrix. On the other hand, a multimodal precipitate distribution tends to become unimodal at low aging temperatures and bimodal at high aging temperatures. Interestingly, the activation energy is calculated for the coarsening of large precipitates in multimodal distribution and is found to vary with aging time.

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confidence: 89%

“…Additional data points at 1413 K (1140°C) after 30 minutes up to 24 hours are used from an earlier work. [18] A highly linear correlation, pointed out by the R-squared values of the first set of aging treatments at 1223 K (950°C), 1393 K (1120°C), and 1413 K (1140°C), indicates the applicability of Eq. [1] to the superalloy IN738LC.…”

Section: Kineticsmentioning

confidence: 99%

Multimodal Precipitation in the Superalloy IN738LC

Balikci

Erdeniz

2010

Metall Mater Trans A

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“…2. Carburization of inner wall caused to formation carbide precipitates in the austenite matrix and the formation of grain boundary carbides, thus reducing the ductility and fatigue life of the material [13].…”

Section: Reason Of Failurementioning

confidence: 99%

Failure Analysis of Ethylene Cracking Tube

Tari

Najafizadeh

Aghaei

et al. 2009

J Fail. Anal. and Preven.

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Radiant tubes of an ethane furnace at a petrochemical plant fabricated from an austenitic heat resistant steel casting (HP grade) failed along longitudinal direction after a fraction of anticipated service life. To study the cause of failure, microstructures of as-received and used tubes were investigated by optical and scanning electron microscopy and the microchemical composition of tubes and precipitated carbide were determined by energy dispersive X-ray (EDS). Also, the morphology of deposited coke particles was determined by SEM/EDS. Finally to measure the extent of carbon penetration, hardness testing was performed on the inner and outer surface of tube. The experimental results show that the improper coking and decoking cycles remove the protective oxide layer (Cr 2 O 3 ) that forms on the exposed surfaces and that, with this layer removed, the coke could easily deposit on inner, non-protected surface. The carbon diffusion into the metal was accelerated with deposited coke and caused microstructural degradation and drastically reduced the ductility of material at high temperatures.

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“…Morphology of precipitates can have important effect on the mechanical behaviour [6]. Especially, needle like precipitates are more likely to reduce the ductility and toughness [10].…”

Section: Effect Of Number and Morphology Of Precipitatesmentioning

confidence: 99%

“…The presence of rphase not only results in harmful influence on the mechanical properties of the material , but also reduces its corrosion resistance by removing chromium and molybdenum from the austenitic matrix [1][2][3][4][5]. It is well known that morphology, size and distribution of precipitates give rise to different effects on the mechanical behaviour of austenitic stainless steels [6,7]. So it is necessary to understand the metallurgical process taking place in the material under elevated temperature for better safety and economy.…”

Section: Introductionmentioning

confidence: 99%