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Title: Fatigue crack initiation, slip localization and twin boundaries in a nickel-based superalloy

Abstract

The study of fatigue in metals, and fatigue initiation specifically, lends itself to analysis via an emerging set of characterization and modeling tools that describe polycrystals on the meso- or microstructural length scale. These include three-dimensional characterization techniques, elastic anisotropic and visco-plastic stress models, new approaches to the statistical description of stress and strain distributions, synthetic microstructure modeling, and improved tools for manipulating the large datasets generated. A specific example of analysis in both 2D and 3D of fatigue cracks in a nickel-based superalloy is given where all the cracks are effectively coincident with coherent twin boundaries. A spectral method is used to analyze the stress state based on a fully anisotropic elastic calculation. The results indicate that, although a high resolved shear stress is associated with the locations of the observed cracks, the length of the trace of the twin boundary is more strongly correlated with crack formation.

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Air Force Research Laboratory (AFRL) - Air Force Office of Scientific Research (AFOSR); National Science Foundation (NSF); Air Force Research Laboratory (AFRL)
OSTI Identifier:
1392070
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Current Opinion in Solid State and Materials Science; Journal Volume: 18; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
Crack initiation; superalloy

Citation Formats

Stein, Clayton A., Cerrone, Albert, Ozturk, Tugce, Lee, Sukbin, Kenesei, Peter, Tucker, Harris, Pokharel, Reeju, Lind, Jonathan, Hefferan, Christopher, Suter, Robert M., Ingraffea, Anthony R., and Rollett, Anthony D. Fatigue crack initiation, slip localization and twin boundaries in a nickel-based superalloy. United States: N. p., 2014. Web. doi:10.1016/j.cossms.2014.06.001.
Stein, Clayton A., Cerrone, Albert, Ozturk, Tugce, Lee, Sukbin, Kenesei, Peter, Tucker, Harris, Pokharel, Reeju, Lind, Jonathan, Hefferan, Christopher, Suter, Robert M., Ingraffea, Anthony R., & Rollett, Anthony D. Fatigue crack initiation, slip localization and twin boundaries in a nickel-based superalloy. United States. doi:10.1016/j.cossms.2014.06.001.
Stein, Clayton A., Cerrone, Albert, Ozturk, Tugce, Lee, Sukbin, Kenesei, Peter, Tucker, Harris, Pokharel, Reeju, Lind, Jonathan, Hefferan, Christopher, Suter, Robert M., Ingraffea, Anthony R., and Rollett, Anthony D. Fri . "Fatigue crack initiation, slip localization and twin boundaries in a nickel-based superalloy". United States. doi:10.1016/j.cossms.2014.06.001.
@article{osti_1392070,
title = {Fatigue crack initiation, slip localization and twin boundaries in a nickel-based superalloy},
author = {Stein, Clayton A. and Cerrone, Albert and Ozturk, Tugce and Lee, Sukbin and Kenesei, Peter and Tucker, Harris and Pokharel, Reeju and Lind, Jonathan and Hefferan, Christopher and Suter, Robert M. and Ingraffea, Anthony R. and Rollett, Anthony D.},
abstractNote = {The study of fatigue in metals, and fatigue initiation specifically, lends itself to analysis via an emerging set of characterization and modeling tools that describe polycrystals on the meso- or microstructural length scale. These include three-dimensional characterization techniques, elastic anisotropic and visco-plastic stress models, new approaches to the statistical description of stress and strain distributions, synthetic microstructure modeling, and improved tools for manipulating the large datasets generated. A specific example of analysis in both 2D and 3D of fatigue cracks in a nickel-based superalloy is given where all the cracks are effectively coincident with coherent twin boundaries. A spectral method is used to analyze the stress state based on a fully anisotropic elastic calculation. The results indicate that, although a high resolved shear stress is associated with the locations of the observed cracks, the length of the trace of the twin boundary is more strongly correlated with crack formation.},
doi = {10.1016/j.cossms.2014.06.001},
journal = {Current Opinion in Solid State and Materials Science},
number = 4,
volume = 18,
place = {United States},
year = {Fri Aug 01 00:00:00 EDT 2014},
month = {Fri Aug 01 00:00:00 EDT 2014}
}
  • In recent years, the design requirements of advanced gas turbine engines have led to the development of directionally solidified single crystal nickel-based superalloys. Among these alloys, CMSX-4 is a new second-generation single crystal nickel-based superalloy containing rhenium. This alloy has been developed from the first-generation CMSX alloys. It has superior hot corrosion resistance and higher creep-rupture strength than first-generation single crystal nickel-based superalloys and is an attractive candidate for complex components that require continuous exposure to very high temperatures. Due to its potential applications in turbine blades, rotors and nuclear reactors, etc., the fatigue crack growth rate (FCGR) and fatiguemore » threshold (FT) data of this material are extremely important for safe life prediction as well as failure safe design at elevated temperatures. Preliminary studies by these authors have indicated that this material is probably undergoing dynamic strain aging (DSA) in the temperature range of 260 to 800 C. However, the effect of DSA on FCGR and FT is not well known or established for single crystal nickel-based superalloys. The objective of this investigation was to determine the effect of DSA on FCGR and FT of CMSX-4 at the temperature range of 650 and 800 C.« less
  • The fatigue crack growth behavior of an experimental, single crystal alloy, of equivalent nominal chemical composition to Inconel 718 is presented. Fracture modes under cyclic loading were determined by scanning electron microscopy. The results of the fractographic analyses are presented on a fracture mechanism map that shows the dependence of the fatigue fracture mechanisms on the maximum stress intensity factor, K[sub max], and the stress intensity factor range, [Delta]K. Crack-tip deformation mechanisms associated with fatigue crack growth were studied using transmission electron microscopy. The relative effects of [Delta]K and K[sub max] on the fatigue crack growth behavior of this materialmore » are discussed within the context of a two-parameter crack growth law. The influence of grain boundaries on the fatigue crack growth resistance of materials such as Inconel 718 is also discussed in light of the results of this investigation.« less
  • An investigation was carried out to determine the growth kinetics of [gamma][prime] precipitates in a newly developed single-crystal nickel-base superalloy containing rhenium (CMSX-4G). The investigation also examined the influence of [gamma][prime] precipitates (size and distribution) on fatigue crack growth behavior of the material in a room-temperature ambient atmosphere. The influence of load ratio on fatigue threshold of the material and crack growth mechanisms in fatigue was also studied. Compact tension specimens were prepared from a single-crystal nickel-base superalloy, CMSX-4G, with the <001> crystallographic direction. These specimens were given two different heat treatments to produce two different [gamma][prime] size precipitates. Fatiguemore » crack growth behavior of these materials was studied at three different load ratios (R = 0.10, 0.50, and 0.90) in room-temperature ambient atmosphere. The results of the present investigation demonstrate that rhenium additions in CMSX-4G substantially lowers the [gamma][prime] coarsening kinetics of this alloy. The smaller [gamma][prime] precipitate size was found to be beneficial for fatigue resistance and has resulted in a higher fatigue threshold and lower fatigue crack growth rate in the threshold region. The fatigue threshold was found to decrease with an increase in load ratio. The crack growth mechanism in the threshold region was found to occur by a combination of microvoid coalescence and striations.« less
  • CMSX-4 is a recently developed rhenium containing single crystal nickel-based superalloy. This alloy has potential applications in many critical high-temperature applications such as turbine blades, rotors, nuclear reactors, etc. The fatigue crack growth rate and the fatigue threshold data of this material is extremely important for accurate life prediction, as well as failure safe design, at elevated temperatures. In this paper, the fatigue crack growth behavior of CMSX-4 has been studied at 650 C. The investigation also examined the influence of [gamma][prime] precipitates (size and distribution) on the near-threshold fatigue crack growth rate and the fatigue threshold. The influence ofmore » load ratio on the fatigue crack growth rate and the fatigue threshold was also examined. Detailed fractographic studies were carried out to determine the crack growth mechanism in fatigue in the threshold region. Compact tension specimens were prepared from the single crystal nickel-based superalloy CMSX-4 with [001] orientation as the tensile loading axis direction. These specimens were given three different heat treatments to produce three different [gamma][prime] precipitate sizes and distributions. Fatigue crack growth behavior of these specimens was studied at 650 C in air. The results of the present investigation indicate that the near-threshold fatigue crack growth rate decreases and that the fatigue threshold increases with an increase in the [gamma][prime] precipitate size at 650 C. The fatigue threshold decreased linearly with an increase in load ratio. Fractographs at 650 C show a stage 2 type of crack growth along [l brace]100[r brace] type of crystal planes in the threshold region, and along [l brace]111[r brace] type of crystal planes in the high [Delta]K region.« less
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