Elaboration of Nickel Aluminide Diffusion Coatings: Application to Oxidation Resistance

2008 ◽  
Vol 595-598 ◽  
pp. 41-49 ◽  
Author(s):  
Céline Choux ◽  
Sébastien Chevalier ◽  
Yannik Cadoret
Keyword(s):  
High Temperature ◽  
Nickel Aluminide ◽  
Diffusion Mechanism ◽  
Alumina Scale ◽  
Organic Chemical ◽  
Material Surface ◽  
Protective Oxide ◽  
Diffusion Coatings ◽  
Aluminide Coatings ◽  
Α Al2o3

Aluminide diffusion coatings are widely used in aeronautic domain. Nickel based superalloys present good mechanical properties and creep resistance at high temperature but their corrosion resistance is somewhat poor. In order to enhance their lifetime at high temperature, aluminide coatings can be applied on alloy surface. Aluminium present on material surface can form, at high temperature, alumina scale which is a protective oxide scale. In the present study, nickel aluminide coatings were carried out by aluminisation in a single step pack cementation process on nickel based superalloys 600 and AM1. Ni-Al intermetallic was obtained in each case. Oxidation tests were carried out at 900°C in air under atmospheric pressure. At this temperature, transient alumina as γ-Al2O3 and θ-Al2O3 appear on surface and are less protective than the stable α- Al2O3. Reactive elements can enhance α-Al2O3 nucleation and change diffusion mechanism during oxidation leading to a better adherence of alumina scale. In the present work, yttria was introduced by Metal-Organic Chemical Vapour Deposition (MOCVD) prior to the aluminisation. Yttria doped and undoped sample behaviours were compared under oxidising atmospheres.

Aluminide Coating Formation on Internal Passages of GTD-111 Superalloy by Slurry Technique

2008 ◽  
Vol 595-598 ◽  
pp. 185-190 ◽  
Author(s):  
K. Shirvani ◽  
Amir Firouzi
Keyword(s):  
High Temperature ◽  
Aluminide Coating ◽  
Air Cooling ◽  
Diffusion Coatings ◽  
Aluminide Coatings ◽  
Internal Surfaces ◽  
Nial Phase ◽  
The Matrix ◽  
Coating Formation ◽  
Cooled Blade

The diffusion aluminide coatings are widely used in the air-cooling passages to protect their surfaces against high temperature corrosion. In this study plain and Si-modified aluminide coatings were applied by slurry technique on internal surfaces of Ni-base GTD-111 superalloy cylindrical specimens derived from a gas turbine air-cooled blade. The slurries containing Al or Al plus Si powders were applied on internal surfaces by injection method. Then, the samples were heated to high temperature (800-1000°C) to form the coatings. Optical, SEM-EDS, and XRD were utilized for characterizing microstructures and phase compositions of the coatings. The thicknesses of applied coatings on internal surfaces were in the range of 30-50 μm that meets specifications for diffusion coatings in such application (i.e. 25-756m). The examinations demonstrated that both coating types were contained β-NiAl phase as the matrix. The uniformities of coatings applied on different surface positions of passageway were determined. In addition, the effects of time and temperature of coating process as well as mass of dried slurry on the coating thickness were also discussed.

Effect of diffusion coatings on the high temperature properties of nickel-chromium-superalloys

2018 ◽  
Vol 32 (19) ◽  
pp. 1840056 ◽  
Author(s):  
Byeong Woo Lee
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Aluminide Coating ◽  
Pure Aluminum ◽  
Protective Layer ◽  
Nitrogen Atmosphere ◽  
Silicide Coating ◽  
Diffusion Coatings ◽  
Aluminide Coatings ◽  
Negative Role

The halide-activated pack cementation method was utilized to deposit aluminide or silicide coatings on Inconel 617 and Hastelloy X superalloys. Aluminide and silicide diffusion coatings were formed at 850[Formula: see text]C for 2 h in nitrogen atmosphere, using a pack mixture containing pure aluminum (Al) or silicon (Si) and aluminum oxide (Al2O3) powders with activators of NH4Cl and AlF3. Aluminide-coated alloys showed homogeneous and uniform microstructures. Al diffused into the alloy inwards and aluminide diffusion coatings of [Formula: see text]17 [Formula: see text]m thick were formed inside the alloy. It was shown that the Al coatings played a key role in blocking off the excessive corrosion products at a high temperature for the alloys. The enhanced thermal stability and improved wear resistance were achieved in the aluminide coatings. In contrast to the aluminide coating, the silicide coating played a negative role, unable to provide the protective layer. The microstructural evolution and thermal stability of the aluminide- and silicide-coated alloys have been elucidated.

Diffusion Enhanced Rumpling Associated with Martensitic Transformation upon Cycling of Aluminide Bond-Coats

2009 ◽  
Vol 289-292 ◽  
pp. 227-233 ◽  
Author(s):  
B. Bouchaud ◽  
J. Balmain ◽  
F. Pedraza
Keyword(s):  
Martensitic Transformation ◽  
Oxide Scale ◽  
Alumina Scale ◽  
Scale Spallation ◽  
Protective Oxide ◽  
Isothermal Exposure ◽  
Growth Stresses ◽  
Bond Coats ◽  
Aluminide Coatings ◽  
L10 Structure

In this work, β-NiAl aluminide coatings (cubic B2 structure) deposited on a DS substrate have been isothermally as well as cyclically oxidised at 1100°C for up to 240 h to study the diffusion mechanisms associated with the growth of the oxide scales. A 24 h cycle has been shown to promote enhanced Al depletion, thus requiring a sufficient Al flux to maintain a protective oxide scale. Glancing incidence X-ray diffraction (GI-XRD) combined to electron microscopy (FEG-ESEM / EDS) has been carried out to characterize the evolution of the phases induced by the progressive Al depletion into the coating. The results show that upon cycling, specimens undergo significant oxide scale spallation and increased roughness that can be ascribed to both the growth stresses and the phase transformation contribution whereas the coating has barely evolved after 240 h of isothermal exposure. In particular, the martensitic transformation (tetragonal L10 structure) that accompanies thermal cycling was found to be much more significant than the evolution of the γ’-Ni3Al (cubic L12 structure) phase over the same thermal cycle and therefore the B2 to martensite transformation could originate the progressive roughening of the surface. Conversely, upon isothermal exposure, the coating exhibited a typical alumina scale with almost no spallation and the appearance of rumples.

High temperature reactivity of nickel aluminide diffusion coatings

2008 ◽  
Vol 16 (1) ◽  
pp. 1-9 ◽  
Author(s):  
C. Choux ◽  
A.J. Kulińska ◽  
S. Chevalier
Keyword(s):  
High Temperature ◽  
Nickel Aluminide ◽  
Diffusion Coatings

Effect of Polishing Treatment on Rumpling of Oxide Scales on NiPtAl Coatings with Different Pt-Content

2013 ◽  
Vol 662 ◽  
pp. 383-386
Author(s):  
Peng Song ◽  
Jian Sheng Lu
Keyword(s):  
High Temperature ◽  
Nickel Aluminide ◽  
Aluminide Coating ◽  
Temperature Cycling ◽  
Oxide Surface ◽  
Temperature Oxidation ◽  
Aluminide Coatings ◽  
Temperature Exposure ◽  
Engine Components ◽  
Surface Morphologies

Pt-modified nickel aluminide coatings have been more widely used for protection of jet-engine components against high-temperature oxidation. The coating rumpling of two Pt-content NiPtAl coatings was studied in this paper during high temperature exposure. The results indicated that the NiPtAl coating grains size made a great contribution to the oxide surface morphologies, especially rumpling. Smaller grain size within high-Pt coating indicated a denser rumpling compared to low-Pt coating due to PtAl2 formation in the earlier coating. The failed local alumina at the ridges was also found on the low-Pt coating after cyclic oxidatioin. It was found that polished treatment resulted a comparatively flat and homogeneous oxide layer compared to as-received coatings. The temperature cycling could promote the aluminide coating rumpling, however, the polished treatment could not completely eliminate the roughening.

Monitoring Diffusion Coating Aging With Multi-Frequency Eddy Current MWM Sensors

2005 ◽  
Author(s):  
Vladimir Zilberstein ◽  
Robert Lyons ◽  
Andrew Washabaugh ◽  
Dave Grundy ◽  
Chris Craven ◽  
...  
Keyword(s):  
Eddy Current ◽  
Gas Turbines ◽  
Nickel Aluminide ◽  
Single Channel ◽  
Diffusion Coating ◽  
Diffusion Coatings ◽  
Aluminide Coatings ◽  
Wide Range ◽  
Before And After

Diffusion coatings are widely used to protect hot gas path components in land-based gas turbines and jet engines. Effective nondestructive assessment of the aged coating and substrate condition is critical for support of refurbish/replace/run decisions. In this paper, we present results on aging characterization of nickel aluminide and platinum aluminide coatings. The measurements were performed using a Meandering Winding Magnetometer (MWM®) eddy current sensor over a wide range of frequencies. Single-channel MWM sensors and multichannel imaging MWM-Arrays permit tracking of features of interest for a population of components and provide new capabilities for inspecting gas turbine components. These conformable sensors allow convenient manual and automated inspection on complex surfaces. Results on coating aging assessment suggest that the multiple frequency MWM technique can be implemented for characterization of diffusion coatings and base metals before and after component refurbishment.

Multifunction High Temperature Coating System Based on Aluminium Particle Technology

2008 ◽  
Vol 595-598 ◽  
pp. 769-777 ◽  
Author(s):  
Vladislav Kolarik ◽  
Maria Juez-Lorenzo ◽  
M. Anchústegui ◽  
Harald Fietzek
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Diffusion Layer ◽  
High Surface ◽  
Alumina Scale ◽  
Thermal Barrier ◽  
Coating System ◽  
Initial State ◽  
Α Al2o3

Spherical Al particles sized in the range of 2 to 5 μm were deposited with an organic binder by brushing on the austenitic steel X6 CrNi 18-10 (Alloy 304H). The coated samples were annealed in air at 400°C for 1 h in order to expel the binder. For studying the oxidation behaviour in air, isothermal experiments were performed at 700°C and 900°C with oxidation times of 5 h, 100 h and 1000 h. The oxide formation was studied in situ by high temperature X-ray diffraction (HTXRD) up to 100 h. Field emission scanning electron microscopy (FE-SEM) was applied to investigate the surface and the cross-section of the particle coating. During oxidation, the stable α-Al2O3 was identified in situ by HT-XRD on all studied samples at both temperatures. No meta-stable alumina phases were found. In the initial state, 2 h at 900°C, the Al particles are completely oxidised to hollow alumina spheres, controlled predominantly by the reaction due to the small particle size and relatively high surface portion. Simultaneously, the Alrich diffusion layer is formed in the substrate. On further exposure, a thin protective alumina scale continues growing on the top of the diffusion layer. After exposure to both 700°C and 900°C, a coating structure was encountered, which consists of a quasi-foam top coat from conjoint hollow spherical alumina particles and an Al-rich diffusion layer below. The quasi-foam top coat has the potential to effectuate as thermal barrier by gas phase insulation, while the diffusion layer below serves as protective coating against oxidation. The approach by particle size processing opens a potential for obtaining a complete thermal barrier coating system in one manufacturing step. The coating properties can be adjusted by parameters like selection of source metal/alloy, particle size, substrate, binder and heat treatment.

Diffusion Coefficient of Nickel in Ni2Al3 Intermetallic Compound

2014 ◽  
Vol 1025-1026 ◽  
pp. 731-736
Author(s):  
Marut Khieokae ◽  
Ratchawit Hanamornroongruang ◽  
Ratachris Ramasoot ◽  
Akadej Taechakaesaree ◽  
Paphawit Ngamchaliew ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
High Temperature ◽  
Nickel Aluminide ◽  
Nickel Alloys ◽  
Diffusion Mechanism ◽  
Compound Layer ◽  
Nickel Surface ◽  
Turbine Engine ◽  
Activation Energy For Diffusion ◽  
Flux Difference

Nickel alloys have been widely used for high temperature applications such as gas turbine engine, turbine blade and many high temperature resistance components. Aluminizing is one of effective to increase oxidation resistant of nickel alloys by forming nickel aluminide compounds on nickel surface. Nickel aluminide is formed by the diffusion mechanism. This research aims to study the diffusion behavior of nickel in Ni2Al3compound. The diffusion coefficient is determined using Ni/Al diffusion couple forming Ni2Al3and NiAl3phases. The temperatures under study are 873, 973, and 1073 K, which are at above and below melting point of aluminum. Determination of diffusion coefficient of Ni in Ni2Al3is from mass balance concept: flux difference at interphase causes accumulation of atoms in compound layer, which as be derived as: dxαβ/dt = [1/(nβ-nα)] * [Dα*(dnα/dx) - Dβ*(dnβ/dx)] From this equation, diffusion coefficient of Ni in Ni2Al3at 873 and 1073 K are calculated as 6.243×10-11and 6.82×10-9m2/s, respectively. From Arrhenius equation of diffusivity, D = Doexp (-Q/RT), the activation energy for diffusion of nickel in Ni2Al3is found to be 183 kJ/mol. The result obtained in this research is of great use in controlling aluminizing process.

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