Characterization of phases of aluminized nickel base superalloys

Wöllmer, Silke; Zaefferer, Stefan; Göken, Mathias; Mack, Thomas; Glatzel, Uwe

doi:10.1016/s0257-8972(02)00843-5

Cited by 73 publications

(44 citation statements)

References 27 publications

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“…Further investigations to improve the statistics (repeated creep tests) will be carried out in the near future to eliminate material scatter. Microstructural observations especially of surface features will be carried as described in [13] in order to further understand the mechanics leading to these observations.…”

Section: Discussionmentioning

confidence: 99%

“…Specimens were tested with an 40 μm aluminum coating and without coating. Aluminum coating was carried out by an aluminum pack cementation process (> 900°C) with subsequent heat treatment (730°C for 24 h), for details see [13]. The initial cross section of the non-coated sample was used to calculate the necessary load for both non-coated and aluminized samples.…”

Section: Methodsmentioning

confidence: 99%

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Creep Behavior of Thick and Thin Walled Structures of a Single-Crystal Nickel-Base Superalloy at High Temperatures: Experimental Method and Results

Hüttner¹,

Völkl²,

Gabel³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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Creep behavior of the single crystal nickel-base superalloy René N5 is investigated as a function of material thickness. The results point out that reducing the thickness from 1.0 to 0.2 mm leads to both shorter creep lives and much higher overall creep strain rates of thin specimens. The orientation of the specimen is an important factor too but has a weaker influence on creep behavior under the given test conditions than the specimen thickness. IntroductionSingle crystal nickel-base superalloys are used in blades and vanes of stationary gas turbines and aero engines. Their lifetimes are mainly limited by fatigue, creep and hot corrosion at elevated service temperatures. To increase lifetime a possible strategy is to reduce the material temperature by cooling. In order to optimize both the cooling efficiency and the weight of fast rotating turbine blades a general trend is to reduce the wall thickness of the hollow investment casting parts. The relation between creep properties and section thickness was rarely investigated [1][2][3][4][5][6][7][8][9][10]. For the polycrystalline nickel-base superalloy PWA 1484 Duhl [1] found a five fold reduction of creep rupture life if the specimen thickness is diminishing from 4 to 0.5 mm which mainly depends on grain size and micro structural defects. Doner and Heckler [3,4] observed in uncoated single crystal CMSX-3 a 30% loss in creep rupture life if the wall thickness was reduced from 3.18 to 0.76 mm at 982°C and if the stress level was below 275 MPa. They also found that the time to reach 1% strain was unaffected by wall thickness at a constant stress level. Seetharaman and Cetel [6] reported similar results for single crystal PWA 1484 with wall thicknesses of 1.76 and 0.38 mm respectively and stresses below 275 MPa at 982°C. They concluded that oxidation and the more constrained plastic deformation are the major contributions for early failure of thin specimens. Doner and Heckler [3,4] found that creep rupture properties of aluminized nickel-base superalloys are less influenced by the specimen thickness. By contrast Seetharaman and Cetel [6] mentioned a loss of creep rupture lifetime of 30-40% with a thickness reduction from 1.52 to 0.25 mm for coated Knowledge and understanding of the creep behavior is a fundamental prerequisite for component life-time predictions. Therefore the effect of thickness reduction on the creep properties of uncoated and aluminized single crystal nickel-base superalloy René N5 is investigated in this study. In addition deviations from the [001] orientation are incorporated into this study which is part of a ongoing research carried out for the next years.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Creep Behavior of Thick and Thin Walled Structures of a Single-Crystal Nickel-Base Superalloy at High Temperatures: Experimental Method and Results

Hüttner¹,

Völkl²,

Gabel³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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“…In addition to these, a mixed zone (MZ) was identified in the present research work (see scheme in Fig.1b) as the layer where these particles appear together with substrate phases (γ and γ'). The additional third layer was differently considered in literature: sometimes it was omitted, including it into IDZ or into substrate [6,4,11], sometimes it was widened to include the whole Al-enriched substrate layer [11] and in other cases it was considered as a secondary reaction zone [8].…”

Section: Resultsmentioning

confidence: 99%

“…Several particles mainly containing W, Re, Ta and Cr, roughly corresponding to chemistry of phases reported in [9] were identified at the internal side of the IDZ. Other authors referred the presence of several phases, characterized by the same elements in the outer IDZ [4], so they divided it into sub-layers. The differentiation between IDZ and MZ was not always clear, depending on the substrate orientation.…”

Section: Resultsmentioning

confidence: 99%

“…Further, the microstructural features of diffusion layered coatings in single crystal are potentially affected by substrate lattice orientation with respect to the external surface. As a matter of fact, solid state diffusion is related by crystallographic orientation of the phase within which it occurs and orientation relationships between lattices in a layered structure exist: (for the present case <100> γ' // <100> γ , while the interface requirement (111) γ' //(110) β are met by three specific β grain orientations with respect to the substrate lattices [4]). The effect of substrate orientation on the overall coating thickness of CM 247 LC alloy was recently investigated in [10].…”

Section: Introductionmentioning

confidence: 86%

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Evolution of the Diffusion Layer in a CMSX4 Single Crystal Superalloy

Gariboldi

Han

Longo³

et al. 2011

AMR

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Aluminising processes are well-known techniques industrially adopted to enrich of aluminium the surface layers of Ni-based alloys thus improving their resistance to environmental interaction at high-temperature. The results of aluminising processes are typically described in terms of the presence, compositions and thickness of the sequence of layers at the surface of the treated parts. Following this approach, the microstructural features of the diffusion layers obtained under different holding times via vapour-phase type high-temperature low-activity process were experimentally investigated on single crystal CMSX4 alloy. The attention was particularly focused on the effect of the crystallographic orientation of the crystal on the coating features. The evolution of the diffusion layers under different process conditions was then taken into account.

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Local Fracture Toughness and Residual Stress Measurements on NiAl Bond Coats by Micro Cantilever and FIB Based Bar Milling Tests

Webler¹,

Krottenthaler²,

Neumeier³

et al. 2012

Superalloys 2012

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The mechanical behavior of bond coats depends on their chemical composition. Important for the mechanical behavior is the Al content of β-NiAl based coatings. Additionally, internal stresses are present and change during thermal cycling. Therefore bond coats with different Ni and Al content in the as-coated and thermally cycled state are investigated. For the first time, new small scaled methods are used to obtain fracture toughness and internal stresses of real bond coat systems. Micro cantilever bending and stress relaxation tests were performed on a local scale by employing focused ion beam milling. Additionally, the influence of NiAl composition on Young's modulus and hardness is studied by nanoindentation. Results show an increase of Young's modulus with Al content. In off-stoichiometric NiAl a higher hardness and fracture toughness than in binary NiAl is found. The internal stresses change from tensile in as-coated to compressive stresses in thermally cycled bond coats, respectively.

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Characterization of phases of aluminized nickel base superalloys

Cited by 73 publications

References 27 publications

Creep Behavior of Thick and Thin Walled Structures of a Single-Crystal Nickel-Base Superalloy at High Temperatures: Experimental Method and Results

Creep Behavior of Thick and Thin Walled Structures of a Single-Crystal Nickel-Base Superalloy at High Temperatures: Experimental Method and Results

Evolution of the Diffusion Layer in a CMSX4 Single Crystal Superalloy

Local Fracture Toughness and Residual Stress Measurements on NiAl Bond Coats by Micro Cantilever and FIB Based Bar Milling Tests

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