718 Superalloy Forging Simulation: A Way to Improve Process and Material Potentialities

Spath, N.; Zerrouki, Véronique; Poubanne, P.; Guedou, J.Y.

doi:10.7449/2001/superalloys_2001_173_183

Cited by 18 publications

(24 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this version, the gas turbine disk is typically produced by 'hot-die' forging followed by aging. Grain refinement during forging is critical in this process for improved LCF life of the disk [3,4]. It is desirable that the fatigue critical disks are produced with a fine grained microstructure in the range of 5-20 μm to maximize fatigue benefits.…”

Section: Introductionmentioning

confidence: 99%

Surface Effects on Low Cycle Fatigue Behavior in IN718 Alloy

Bhowal¹,

Stolz²,

Wusatowska-Sarnek³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

View full text Add to dashboard Cite

Superalloys used in gas turbine engine rotating components require superior low cycle fatigue (LCF) properties, but often, the intrinsic LCF capability of the rotor, as determined by laboratory specimen tests, is limited by presence of fine particles such as carbides, borides and ceramic inclusions, as well as, pores, voids, and large grains in the alloy. Further, manufacturing processes such as turning, milling, and broaching can limit LCF life if they introduce surface damage and/or tensile residual stress. In IN718, prior studies have shown that fatigue initiation from MC carbides is promoted at lower test temperature and high stress, and the LCF life is significantly reduced. The present study investigates the effect of machining that can introduce carbide damage on LCF life, and a few post-machine processing methods for LCF recovery. The IN718 material used in this study came from a gas turbine disk forging that was directly aged without the conventional solution heat-treatment. The microstructure was fine-grained with an average grain size of 11 μm. Smooth and notched LCF properties were evaluated with machined and polished surfaces at test temperature and stress that promoted carbide initiation of fatigue cracks.Majority of the tests were performed at temperature of 560 K and at stresses of 1102 and 1240 MPa for smooth, and nominal stresses of 595 and 650 MPa for notched specimens. The min to max stress ratio (R) was 0.05. The cycles to failure were analyzed in terms of machining effect on surface carbides, and the fatigue initiation sites were studied by scanning electron microscopy (SEM). Smooth LCF specimens included asmachined (lathe-turned) and polished (600 grit SiC) surfaces and the notched LCF specimens included single-point bored (SPB) and media-polished notch surfaces. Lathe-turning and SPB cracked or damaged surface and subsurface carbides, considerably impacting the LCF life by factors of 3-15X (depending on test conditions). For a smooth lathe-turned surface, shot peening was effective in recovering LCF life by 5-10X at minimum over the as-machined surface. Some conventional post-machine processes for holes, such as mechanical honing, extrude hone and jig grinding and their influence on LCF life were studied as well.

show abstract

Section: Introductionmentioning

confidence: 99%

Surface Effects on Low Cycle Fatigue Behavior in IN718 Alloy

Bhowal¹,

Stolz²,

Wusatowska-Sarnek³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

View full text Add to dashboard Cite

show abstract

“…In such homogeneous microstructures, the main crack very commonly initiates on a crystallographic cleavage on a grain located on the surface of the specimen [13]. The crack initiation mode is thus very similar to what has been identified on the AGG containing samples.…”

Section: µMmentioning

confidence: 56%

Characterization of Microstructures Containing Abnormal Grain Growth Zones in Alloy 718

Flageolet¹,

Cormier²,

Yousfi³

et al. 2010

7th International Symposium on Superalloy 718 and Derivatives (2010)

View full text Add to dashboard Cite

A well known issue encountered by forgers transforming Alloy 718 consists in the appearance of coarse grain zones during the thermo-mechanical process. Although some industrial solutions have been implemented in order to get rid of this type of microstructural defect, the consequences of the presence of such coarse grained areas on the material's mechanical properties are of great interest.In this work, some zones that have undergone abnormal grain growth (AGG) have primarily been characterized from a microstructural point of view by means of both optical and EBSD observations. Special attention has been paid to grain orientation, grain boundaries and grain size distributions. In addition the effects of these microstructures on 350°C deformation controlled fatigue crack initiation mechanisms and the subsequent lifetime have been assessed as well as on 350°C tensile properties have also been evaluated.The results will be discussed with regard to microstructure/mechanical behavior relationships.

show abstract

“…[1,3,[8][9][10]). The effect of grain size reduction ,assumed to be beneficial on fatigue lives, was more particularly studied for conventional and DA 718 alloys (see e.g.…”

Section: Fatigue Crack Initiation Sitesmentioning

confidence: 99%

“…The effect of grain size reduction ,assumed to be beneficial on fatigue lives, was more particularly studied for conventional and DA 718 alloys (see e.g. [1,2,10]). These studies confirmed that the reduction in grain size produces a significant increase in fatigue life, as shown in Figure 1, where the material is tested at 350°C and a frequency of 1Hz under strain controlled conditions (Rε t =ε min /ε max =0) [10,3].…”

Section: Fatigue Crack Initiation Sitesmentioning

confidence: 99%

“…[1,2,10]). These studies confirmed that the reduction in grain size produces a significant increase in fatigue life, as shown in Figure 1, where the material is tested at 350°C and a frequency of 1Hz under strain controlled conditions (Rε t =ε min /ε max =0) [10,3]. These fatigue studies also revealed that for very low grain size (lower than 10µm) obtained by DA heat treatment the results of fatigue life measurements were largely scattered.…”

Section: Fatigue Crack Initiation Sitesmentioning

confidence: 99%

See 1 more Smart Citation

Probabilistic Life of DA718 for Aircraft Engine Disks

Deyber¹,

Alexandre²,

Vaissaud³

et al. 2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

View full text Add to dashboard Cite

The micro-mechanisms of crack initiation and propagation identified for DA 718, as well as the competition between initiation site types and locations, cannot be accurately accounted for by current certified methods used to establish aircraft engine disks life,essentially phenomenological.Once identified, these micro-mechanisms have been modelized by mesoscopic models using very few parameters and depending strongly on material mechanical behavior. LCF data scatter was mainly attributed to probabilistic nature of particle presence in a given volume, and probability of fracture at the first LCF cycle.In order to describe these effects and develop a model able to account for LCF scatter by the only means of physical mechanisms description, a global macroscopic and probabilistic model has been proposed. This model can be used as a post-processing routine of a finite element analysis.Confrontation of the global probabilistic model to experimental data gathered on notched samples gives good results, and the proposed method shows more realistic than the standard one on the cases exposed. Contrary to the standard method, it allows in addition to determine the predominant initiation site as a function of loading, material behavior and microstructure inherited from forging process, giving way to possible material and forging route optimisation at the design stage, to fulfill given structural life objectives.

show abstract

718 Superalloy Forging Simulation: A Way to Improve Process and Material Potentialities

Cited by 18 publications

References 4 publications

Surface Effects on Low Cycle Fatigue Behavior in IN718 Alloy

Surface Effects on Low Cycle Fatigue Behavior in IN718 Alloy

Characterization of Microstructures Containing Abnormal Grain Growth Zones in Alloy 718

Probabilistic Life of DA718 for Aircraft Engine Disks

Contact Info

Product

Resources

About