The effect of environment and orientation on fatigue crack growth behaviour of CMSX-4 nickel base single crystal at 650 °C

Joyce, Maria; Wu, X.D.; Reed, P.A.S.

doi:10.1016/s0167-577x(03)00423-3

Cited by 35 publications

(37 citation statements)

References 3 publications

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“…Table VI contains two sets of m and C values. This reflects previously reported work [7] that the rate of propagation is influenced by the direction in which the crack is growing on the (001) plane. Clearly cracks growing form a buried flow will be influenced by this apparent anisotropy which in turn will impact on the measured lives.…”

Section: Correlating Pore Impactsupporting

confidence: 90%

The Characterisation and Prediction of LCF Behaviour in Nickel Single Crystal Blade Alloys

Evans¹,

Lancaster²,

Steele³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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The paper focuses on CMSX4 and two experimental alloys, LDSX5 and LDSX6, developed to provide alternative performance attributes. The specific objective in this work was an exploration of the Low Cycle Fatigue (LCF) characteristics of these three alloy variants and the assessment of methods for predicting the observed lives. A comparison of the alloys is presented in relation to their strain control fatigue response and notch fatigue behaviour. Predictions of notch lives are made from the plain specimen data but found to be extremely pessimistic at the lower temperature studied, 650°C. The inaccuracies are attributed to the presence of casting pores. Using measured crack growth data and pore sizes, it is shown that fracture mechanics calculations of residual lives are more appropriate. At 800°C, the higher temperature studied, Walker strain predictions of notch lives are more meaningful. This is explained in terms of the relaxation of stresses at the defects.

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Section: Correlating Pore Impactsupporting

confidence: 90%

The Characterisation and Prediction of LCF Behaviour in Nickel Single Crystal Blade Alloys

Evans¹,

Lancaster²,

Steele³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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“…In Rene N5, preferential oxidation of interdendritic carbides was also observed (Figure 4). A fuller description of the long crack fatigue propagation behaviour in CMSX4 at 650˚C is given in [8]. In brief however, it was observed that the <110> notch direction (Orientation A) has a generally better fatigue crack propagation (fcp) resistance, particularly at lower ∆K levels.…”

Section: Resultsmentioning

confidence: 99%

Comparison of Low Cycle (Notch) Fatigue Behaviour at Temperature in Single Crystal Turbine Blade Materials

Reed¹,

Miller²

2008

Superalloys 2008 (Eleventh International Symposium)

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The scatter in notch fatigue lifetimes of CMSX4 at 650˚C and 725˚C in air and vacuum and with Rene N5 in air at 650˚C is compared under the same (plastic) notch strain range levels. Rene N5 shows shorter lifetimes under equivalent conditions and always exhibits multiple initiation sites. The role of interdendritic porosity in initiating fatigue in both alloys is identified, and the number of initiation sites is found to directly affect fatigue life. In air in CMSX4 and Rene N5, subsurface pores initiate fatigue, and this is believed to be due to the repeated in-filling of surface pores by oxidation product, reducing their associated stress concentration and effectively deactivating them as a fatigue initiation site. Tests in vacuum support this hypothesis as cracks do initiate at surface porosity under vacuum conditions. An attempt to evaluate initiating porosity distributions, has indicated a correlation between total area of initiating porosity and fatigue lifetime, which to some extent may allow for crack coalescence behaviour. A deterministic fracture mechanics based model has been proposed to allow for the effect of pore shape, size and position in determining subsequent fatigue life (and hence scatter). The predictions of the model have been assessed using full factorial design of experiments, assessing the effects of variability in pore shape, size and distance below the notch root, as well as the materials parameters (crack growth laws and K max ) used in the lifing calculation. The model successfully explains some, but not all of the observed scatter in lifetimes.

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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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The effect of environment and orientation on fatigue crack growth behaviour of CMSX-4 nickel base single crystal at 650 °C

Cited by 35 publications

References 3 publications

The Characterisation and Prediction of LCF Behaviour in Nickel Single Crystal Blade Alloys

The Characterisation and Prediction of LCF Behaviour in Nickel Single Crystal Blade Alloys

Comparison of Low Cycle (Notch) Fatigue Behaviour at Temperature in Single Crystal Turbine Blade Materials

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

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