Study of the effect of hydrogen charging on the tensile properties and microstructure of four variant heat treatments of nickel alloy 718

Demetriou, Velissarios; Robson, Joseph D.; Preuß, Michael; Morana, Roberto

doi:10.1016/j.ijhydene.2017.02.149

Cited by 45 publications

(22 citation statements)

References 21 publications

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“…The activation energy of 58 kJ/mol has been proposed as the criterion to determine whether hydrogen, which is already trapped in a site, can be reversibly released or not [42]. However, hydrogen-assisted intergranular cracking is more common in δ decorated grain boundaries [17] [18] [29] [30] (specimen S2 had discrete, and S4 treated for 16 h had continuous δ platelets extending to grains, see Figure 5(c) and Figure 7(b)). The hydrogen binding energy to δ particles is 30 kJ/mol, which is smaller than 58 kJ/mol [40].…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, phase kinetic simulations [13] [14] defined the alloy 718 limitations, which led to the development of controlled microstructure for specific applications [1] [7]. It is possible that for 718 subsea bolts under CP, transgranular oversized nanoprecipitates at the outer periphery (subsurface) may be the primary source for crack initiation and intersection of localized dislocation slip lines (DSLs) [15] [16] [17], which leads to the formation of nanovoids at transgranular regions; later, transgranular nanovoids coalescence propagates to intergranular cracks.…”

Section: Background Problemmentioning

confidence: 99%

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Alloy 718 Subsea Bolt in Relation to Surface Cracking: A Microstructural Perspective

Saleem¹,

Dong²,

Patel³

2020

MSA

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The brittle fracture mode close to the surface of Inconel 718 subsea bolts is closely related to their nanostructure. When the bolts are used subsea under cathodic protection, hydrogen evolves. Intergranular precipitates and points of intersection of slip lines always held responsible for hydrogen enhanced decohesion. However, thus far, little attention has been paid to the bolts manufacturing method and to the characterization of the role of subsurface oversized nanoprecipitates on transgranular surface cracking. As-received subsea bolts were analyzed using multi-scale observation techniques such as focused ion beam milling, scanning electron microscopy, transmission electron microscopy, and in-air strain rate tensile tests. The results further demonstrated that under identical API aging, there was a difference in the morphological precipitation and strength of 718 as a bolt and rectangular billet. For the 718 rectangular billets, discrete intergranular stable δ/MC carbides precipitate and only γ' of 10-20 nm was observed for the bulk and subsurface. Whereas, for the CRA subsea bolt, γ' was approximately 30 nm, γ" was 30-50 nm for the bulk (370 HV); γ' was approximately 50 nm and γ" was 50-100 nm at subsurface (400 HV). As-received subsea bolts were investigated at subsurface (10 µm from the surface) at the thread and shank region, which revealed transgranular sheared oversized ~50 nm γ' (with dislocation networks) and metastable γ" > 100 nm particles, respectively. Thus, an effort was made to develop the hydrogen-assisted surface cracking theory for bolts.

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Section: Discussionmentioning

confidence: 99%

Section: Background Problemmentioning

confidence: 99%

Alloy 718 Subsea Bolt in Relation to Surface Cracking: A Microstructural Perspective

Saleem¹,

Dong²,

Patel³

2020

MSA

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“…Demetriou et al [28] investigated age hardening alloy and reported how the grain growth of different prime phase is attained. At the same age hardening in nickel alloy and its strengthen are compared.…”

Section: Tensile Strength In Gas Turbine Materialsmentioning

confidence: 99%

“…Li-ming TAN et al [32] reported that the increasing the chromium, cobalt, tungsten and Molybdenum content the tensile strength is improved. Demetriou et al [28] investigated age hardening alloy and reported how the grain growth of different prime phase is attained. At the same age hardening in nickel alloy and its strengthen are compared.…”

Section: Tensile Strength In Gas Turbine Materialsmentioning

confidence: 99%

Comprehensive report on Materials for Gas Turbine Engine Components

2019

IJITEE

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In the past three decades, it is very challenging for the researchers to design and development a best gas turbine engine component. Engine component has to face different operating conditions at different working environments. Nickel based superalloys are the best material to design turbine components. Inconel 718, Inconel 617, Hastelloy, Monel and Udimet are the common material used for turbine components. Directional solidification is one of the conventional casting routes followed to develop turbine blades. It is also reported that the raw materials are heat treated / age hardened to enrich the desired properties of the material implementation. Accordingly they are highly susceptible to mechanical and thermal stresses while operating. The hot section of the turbine components will experience repeated thermal stress. The halides in the combination of sulfur, chlorides and vanadate are deposited as molten salt on the surface of the turbine blade. On prolonged exposure the surface of the turbine blade starts to peel as an oxide scale. Microscopic images are the supportive results to compare the surface morphology after complete oxidation / corrosion studies. The spectroscopic results are useful to identify the elemental analysis over oxides formed. The predominant oxides observed are NiO, Cr2O3, Fe2O3 and NiCr2O4. These oxides are vulnerable on prolonged exposure and according to PB ratio the passivation are very less. In recent research, the invention on nickel based superalloys turbine blades produced through other advanced manufacturing process is also compared. A summary was made through comparing the conventional material and advanced materials performance of turbine blade material for high temperature performance.

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“…Hirose et al [14] reported that laser surface softening leads to almost twice the higher ductility of the surface in comparison to the base materials. Heat treatment was used by Demetriou et al [15] to decrease the hydrogen embrittlement. Furthermore, [16] describes that plasma immersion titanium implantation reduces the hydrogen absorption rate and total hydrogen concentration in the volume.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Permeation, and Mechanical and Tribological Behavior, of CrNx Coatings Deposited at Various Bias Voltages on IN718 by Direct Current Reactive Sputtering

et al. 2018

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In the current work, the microstructure, hydrogen permeability, and properties of chromium nitride (CrN x ) thin films deposited on the Inconel 718 superalloy using direct current reactive sputtering are investigated. The influence of the substrate bias voltage on the crystal structure, mechanical, and tribological properties before and after hydrogen exposure was studied. It was found that increasing the substrate bias voltage leads to densification of the coating. X-ray diffraction (XRD) results reveal a change from mixed fcc-CrN + hcp-Cr 2 N to the approximately stoichiometric hcp-Cr 2 N phase with increasing substrate bias confirmed by wavelength-dispersive X-ray spectroscopy (WDS). The texture coefficients of (113), (110), and (111) planes vary significantly with increasing substrate bias voltage. The hydrogen permeability was measured by gas-phase hydrogenation. The CrN coating deposited at 60 V with mixed c-CrN and (113) textured hcp-Cr 2 N phases exhibits the lowest hydrogen absorption at 873 K. It is suggested that the crystal orientation is only one parameter influencing the permeation resistance of the CrN x coating together with the film structure, the presence of mixing phases, and the packing density of the structure. After hydrogenation, the hardness increased for all coatings, which could be related to the formation of a Cr 2 O 3 oxide film on the surface, as well as the defect formation after hydrogen loading. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient by up to 40%. The lowest value of 0.25 ± 0.02 was reached for the CrN x coating deposited at 60 V after hydrogenation.

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Study of the effect of hydrogen charging on the tensile properties and microstructure of four variant heat treatments of nickel alloy 718

Cited by 45 publications

References 21 publications

Alloy 718 Subsea Bolt in Relation to Surface Cracking: A Microstructural Perspective

Alloy 718 Subsea Bolt in Relation to Surface Cracking: A Microstructural Perspective

Comprehensive report on Materials for Gas Turbine Engine Components

Hydrogen Permeation, and Mechanical and Tribological Behavior, of CrNx Coatings Deposited at Various Bias Voltages on IN718 by Direct Current Reactive Sputtering

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