Evaluation of the IN 939 Alloy for Large Aircraft Engine Structures

Sjöberg, Göran; Imamovic, D.; Gabel, Johannes; Cabellero, O.; Brooks, Jeffery; Ferte, J.-P.; Lugan, A.

doi:10.7449/2004/superalloys_2004_441_450

Cited by 16 publications

(4 citation statements)

References 10 publications

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“…For welding purposes, lower hardness is favorable as it leads to lower levels of stress during the welding operation and hence lower risk of crack formation upon welding [3]. Accordingly, the lower hardness of the samples upon over aging rather than solution annealing tends to decrease the formation of liquation cracks in the HAZ [19]. The lowest hardness value (302 HV) was measured for the HTC sample, although the heat treatment time was the longest for this sample, suggesting less than enough time for particle growth.…”

Section: Hardness Of Pre-weld Heat-treated Samplesmentioning

confidence: 99%

“…The over aging operation has been investigated by various researchers [10,11,17,18]. According to a study on IN939, pre-weld heat treatment of the base metal at 1160 °C for 4 h and then cooling at a very slow tend to reduce liquation cracking in the HAZ [19]. In another study on the 939 alloy, pre-weld heat treatment via stepped cooling was proposed to attenuate weld cracking [10].…”

Section: Introductionmentioning

confidence: 99%

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Effects of pre- and post-weld heat treatment cycles on the liquation and strain-age cracking of IN939 superalloy

2019

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Performing heat treatment cycles on precipitation-hardened nickel-based superalloy before and after welding imposes significant contributions to reduced welding cracks. In this study, different pre-and post-weld heat treatment cycles were performed on IN939 alloy to study their effects on microstructure and mechanical properties of the weldments. Three types of pre-weld heat treatment cycles were performed to over age the microstructure and reduce the hardness of the base alloy. Results indicated that hardness of over-age heat-treated samples decreased to about 300 to 315 HV (∼35%). Standard post-weld heat treatments (PWHT) were applied on weldments for strain-age cracking examination. Microstructural investigations showed that the above-mentioned treatments impose significant effects on reducing the liquation and strain-age cracking in heat-affected zone (HAZ) of IN939 weld. Slow furnace cooling heat treatment was found to be the optimal pre-weld heat treatment for the tungsten inert gas (TIG) welding of IN939. Based on the results obtained upon mechanical and microstructural analyses, the four-stage PWHT cycle was found to be a suitable one for IN939 welding. A joint efficiency of 79% was achieved in the optimum pre-and post-weld heat treatment cycles.

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Section: Hardness Of Pre-weld Heat-treated Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of pre- and post-weld heat treatment cycles on the liquation and strain-age cracking of IN939 superalloy

2019

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“…It was developed as a high corrosion resistant material which can operate at temperatures around 850˚C for long periods of time. Intended application was vanes and blades for the industrial land base gas turbine engines [5]. IN939 alloy has been actively used in industrial gas turbines as it was developed for turbine airfoils [6].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Isothermal Oxidation Performance of IN 939 Produced by Casting and Additive Manufacturing

Başbozkurt,

Sarıoğlu

2023

Preprint

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The focus of this study is to compare the isothermal oxidation behavior of IN 939 nickel-based superalloys manufactured by powder bed fusion (PBF) and casting methods. Oxidation experiments were performed on heat treated and non-heat treated IN 939 specimens to reveal the role of heat treatment and manufacturing methods on oxidation behavior. Microstructure of as cast IN 939 had a dendritic structure with gamma prime precipitates. After heat treatment two kinds of gamma prime precipitates were visible. IN 939 manufactured by Powder bed fusion exhibited clearly visible melt pools and no trace of gamma prime precipitates. After heat treatment the melt pools disappeared, and gamma prime precipitates formed. Weight gain results showed that all samples experienced similar mass gain characteristics however, PBF IN 939 with heat treatment showed slightly superior spallation behavior than other samples at 1000˚C. Spallation did not occur at 800 and 900˚C whereas at 1000˚C all samples experienced spallation. All samples followed a parabolic rate law. The activation energies of all samples, calculated for three temperatures (800, 900 and 1000˚C,) were similar, ranging between 260.99-287.51 kJ/mole. XRD and EDS analyses were performed to investigate the oxidation products on the surface. Results indicated that the oxide scale that formed on all IN 939 samples were mainly Cr2O3 and TiO2 in rutile form. In conclusion, based on oxidation weight gain (kinetics) results and oxide scale analysis, additively manufactured IN939 superalloys showed similar oxidation resistance compared to as cast IN939 alloy. These results supported the replacement of as cast manufacturing technique with additive manufacturing techniques for IN 939 alloys with respect to high temperature oxidation resistance.

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“…As the latter acquire random orientation during the solidification process in a conventional cast, fatigue processes that depend on grain orientation become random processes themselves [5,7,8,15]. This is especially true for Nickel (Ni-) based superalloys as are applied in high temperature applications like gas turbine design [32,34]. Superalloys often come with a comparatively coarse grain structure, which prevents homogenization effects at scales which are relevant for the design.…”

Section: Introductionmentioning

confidence: 99%

Probabilistic Modeling of LCF Failure Times Using an Epidemiological Crack Percolation Model

M.¹,

P.²,

L.³

et al. 2022

Preprint

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The analysis of standardized low cycle fatigue (LCF) experiments shows that the failure times widely scatter. Furthermore, mechanical components often fail before the deterministic failure time is reached. A possibility to overcome these problems is to consider probabilistic failure times. Our approach for probabilistic life prediction is based on the microstructure of the metal. Since we focus on nickel-base alloys we consider a coarse grained microstructure, with random oriented FCC grains. This leads to random distributed Schmid factors and different anisotropic stress in each grain. To gain crack initiation times, we use Coffin-Manson-Basquin and Ramberg-Osgood equation on stresses corrected with probabilistic Schmid factors. Using these single grain crack initiation times, we have developed an epidemiological crack growth model over multiple grains. In this mesoscopic crack percolation model, cracked grains induce a stress increase in neighboring grains. This stress increase is realized using a machine learning model trained on data generated from finite element simulations. The resulting crack clusters are evaluated with a failure criterion based on a multimodal stress intensity factor. From the generated failure times, we calculate surface dependent hazard rates using a Monte Carlo framework. We compare the obtained failure time distributions to data from LCF experiments and find good coincidence of predicted and measured scatter bands.

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Evaluation of the IN 939 Alloy for Large Aircraft Engine Structures

Cited by 16 publications

References 10 publications

Effects of pre- and post-weld heat treatment cycles on the liquation and strain-age cracking of IN939 superalloy

Effects of pre- and post-weld heat treatment cycles on the liquation and strain-age cracking of IN939 superalloy

Comparison of Isothermal Oxidation Performance of IN 939 Produced by Casting and Additive Manufacturing

Probabilistic Modeling of LCF Failure Times Using an Epidemiological Crack Percolation Model

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