Fatigue crack growth behavior of a new single crystal nickel-based superalloy (CMSX-4) at 650 C

Sengupta, A.; Putatunda, Susil K.; Balogh, Michael P.

doi:10.1007/bf02645320

Cited by 11 publications

(12 citation statements)

References 20 publications

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“…Many reports were already published describing anisotropic behavior of single crystal superalloys: tensile strength [2,3], fatigue strength [4][5][6], crack propagation behavior [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In regard to crack propagation behavior of single crystal superalloys, it is well known that cracks tend to propagate on {111} slip planes at low temperature, while cracks usually propagate normal to loading direction independent of crystal orientation at high temperature [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…The former cracking behavior is called stage-I cracking, and the latter is called stage-II cracking. Several studies were performed investigating factors that influence crack propagation rate (CPR) and behavior, namely crystal orientation [7][8][9][10][11], temperature [12][13][14], environment [10,[15][16][17], loading frequency [14,18], microstructure and strength of γ' phase [19]. CPR of polycrystals is usually evaluated by mode I stress intensity factor (SIF) range ΔK I .…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Crystal Orientation and Temperature on Fatigue Crack Growth of Ni-based Single Crystal Superalloy

Kagawa¹,

Mukai²

2012

Superalloys 2012 (Twelfth International Symposium)

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Crack propagation tests were performed by using compact specimens made of Ni-based single crystal superalloy CMSX-4. Three types of specimens with different orientation were machined. In all specimens tested at room temperature, cracks propagated along slip planes (stage-I), resulting fracture surfaces composed of slip planes. In specimens tested at elevated temperature, cracks propagated along the machined notch direction (stage-II) at the beginning of the tests. FEM calculations were conducted for evaluating the relations between mode I-III SIFs and crack length for specimen with inclined cracks.Methods for evaluating stage-I and stage-II crack propagation rates were proposed. Stage-I crack propagation rates were correlated within the range of factor of 4 using resolved shear stress intensity factor range which was calculated from shear stress on a slip plane parallel to the stage-I crack plane. Stage-II crack propagation rates of all specimens were correlated in the range of factor of 3 with energy release rate calculated using anisotropic elastic moduli. It was suggested that the difference in the elastic moduli caused by the difference between specimen orientation and tested temperature influenced primarily stage-II crack propagation rate.While stage-II cracking was predominant, stage-I fracture surfaces were initiated near side faces in some specimens, and the areas of the stage-I fracture surface tended to expand to the inner regions of the specimens with crack propagation. The transition from stage-II to stage-I was evaluated by using resolved shear stress intensity factor range under plane stress condition.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Crystal Orientation and Temperature on Fatigue Crack Growth of Ni-based Single Crystal Superalloy

Kagawa¹,

Mukai²

2012

Superalloys 2012 (Twelfth International Symposium)

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“…The dependence of the stage II planar and stage I crystallographic crack growth modes on temperature, frequency and stress intensity range has been well documented for different alloy systems, 11–14 and the crack growth data from notched tests have also established crack growth rates for each of these mechanisms reasonably well 15–18 . However the effect of different crack growth modes on the rate of initiation in plain specimen fatigue testing is not known.…”

Section: Introductionmentioning

confidence: 99%

Fatigue behaviour and lifing of two single crystal superalloys

MacLachlan

Knowles

2001

Fatigue Fract Eng Mat Struct

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A model has been developed to predict the high temperature cyclic life of single crystal superalloys RR2000 and CMSX‐4 under conditions of creep and fatigue. A combined creep–fatigue model is used, although it is found that failure always occurs by creep or fatigue separately, and that creep–fatigue interaction has a minor influence. Microstructural investigation of a series of interrupted high‐ and low‐frequency tests are presented, these are combined with the results of a series of interrupted creep tests to identify the separate and interactive mechanisms of creep and fatigue. When creep damage is present the material behaves homogeneously. Under these conditions crack growth is initiation controlled, the mechanism of failure is surface or casting pore‐initiated planar crack growth followed by shear on crystallographic planes. As the temperature is lowered or the cyclic frequency increased, the material behaves less homogeneously and shear bands are formed during cycling. Crack growth under these conditions is again initiation controlled and failure is by rapid crystallographic crack growth along shear bands. Such a failure is a distinct fatigue failure and occurs when little creep damage is present. Under certain cyclic conditions, mainly those where the crystallographic failure mechanism is dominant, the material shows an anomalous increase in fatigue resistance with temperature up to approximately 950 °C. This behaviour has been quantified by relating it to the effect of strain rate and temperature on the yield strength of the material.

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“…However, such processes have been generally observed during fatigue at much higher temperatures in similar systems, e.g. [15,17,18]. Even though the fracture surface of the 550ºC test was obscured by oxidation and thus fractography could not yield conclusive results, similar processes could be presumed to be active here as well.…”

Section: Effects Of Oxidation On the Fatigue Crack Growth Behaviourmentioning

confidence: 85%

On the mechanism of oxidation-fatigue damage at intermediate temperatures in a single crystal Ni-based superalloy

Evangelou

Soady²,

Lockyer³

et al. 2019

Materials Science and Engineering: A

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The combined effects of environment (oxidation) and mechanical load (fatigue) that control crack propagation in a single crystal Ni-based superalloy have been investigated with particular focus on the intermediate service temperature range. Fatigue tests have been carried out at different frequencies, hold times and environments, to study the parameters influencing crack propagation at 550 o C. The direct current potential drop method was used to monitor the crack growth while STEM-EDS were used to analyse the fracture mode and crack tip regions.It was found that the micro-mechanism of fatigue crack propagation at intermediate temperatures is a complex process with several competing mechanisms acting on the crack tip simultaneously.Crystallographic slip processes by γ' shearing are active at these temperatures while at the same time thermally activated processes that promote crack propagation through the γ channels also take place.In addition, the effects of oxidation were found to be two-fold. It was demonstrated that these temperatures are not high enough to cause macroscopic embrittlement of the crack tip but finger-like protrusions were found to penetrate the material ahead of the crack tip at the nano-scale. The kinetics of such a mechanism were accentuated by the plastic strains at the crack tip, which given enough time, can promote cleavage fracture at the γ/γ' interface. At the same time, given that the crack driving force is lower than a transition value, oxide formation on the crack tip surfaces can bridge the opening of the crack tip and reduce the effective driving force.

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Fatigue crack growth behavior of a new single crystal nickel-based superalloy (CMSX-4) at 650 C

Cited by 11 publications

References 20 publications

The Effect of Crystal Orientation and Temperature on Fatigue Crack Growth of Ni-based Single Crystal Superalloy

The Effect of Crystal Orientation and Temperature on Fatigue Crack Growth of Ni-based Single Crystal Superalloy

Fatigue behaviour and lifing of two single crystal superalloys

On the mechanism of oxidation-fatigue damage at intermediate temperatures in a single crystal Ni-based superalloy

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