Nickel Superalloy Research Articles

Improving mechanical properties of P91 and IN617 dissimilar weld joints for advanced ultra super critical power plants by buttering technique

• Enhancement of mechanical properties using buttering layer for dissimilar weld. • Buttering helps in achieving favorable ductility for dissimilar welds. • With buttering creep rupture life of dissimilar welds has increased. • Buttered dissimilar welds can be implemented for very high-temperature boilers. To improve the mechanical properties of ferritic steel and nickel superalloy, while maintaining economic symmetry, this investigation is performed on fabricating dissimilar metal welds for advanced ultra-supercritical (AUSC) boilers, with a buttering technique. The present work compares a dissimilar weld of IN617 alloy and P91 steel with and without buttering by multipass gas tungsten arc welding for mechanical properties variations, creep strength at elevated temperature, and microstructural evolution. Thin layers of buttering material are applied at the ferritic end, followed by the closure weld consisting of welding a second member to a butter layered component. Further, significant improvement in mechanical properties (tensile strength, toughness, and hardness) and creep rupture life (though the failure remains ductile characterized by dimples variations) 2 to 3 times longer has been found with buttering in contrast with no buttering.

Design and implementation of an ion beam energy degrader for use in the study of nuclear materials

A new design for an ion beam energy degrader has been developed and tested at the Reactor Materials Testing Laboratory at Queen's University. With the use of a dual rack multi-foil system, it is now possible to implant helium uniformly throughout a nickel target to a depth of 33 µm with helium ions. Aluminium foils are used in the degrader with thicknesses ranging from 2–84 µm, causing deceleration of the incident particle and thus a shallower penetration depth in the target with increased Al foil thickness. The design was successfully tested with the helium implantation of nickel superalloy, Inconel X-750. Using transmission electron microscopy, helium bubbles were imaged following an implantation of 8000 appm helium. A continuous formation of helium bubbles was observed with implantation depth, matching the predicted implantation range. The prediction for helium implantation using the aluminium foils to degrade the incident particle is carried out with data generated from SRIM calculations and an inhouse optimization code.

The Impact of Plastic Deformation on the Microstructure and Tensile Strength of Haynes 282 Nickel Superalloy Produced by DMLS and Casting.

The article presents the results of research on the influence of plastic deformation on the microstructure and tensile strength of Haynes 282 nickel superalloy produced by direct metal laser sintering (DMLS) and a conventional technique (casting). Samples were tested for dimensional accuracy using a 3D scanner. Then, the samples were subjected to plastic deformation by rolling. The microstructures of the DMLS and the as-cast samples were analysed using a scanning electron microscope. The strength properties of the samples were determined in a static tensile test. Microhardness measurements of the samples were also performed. Based on the analysis of the dimensional accuracy, it was found that the surface quality of the components produced by DMLS is dependent on the input parameters of the 3D printing process. Using the DMLS method, it is possible to produce Haynes 282 with a fine-crystalline microstructure containing dendrites. The fine-crystalline dendritic microstructure and low porosity showed very good tensile strength compared to the as-cast material. It was also found that the increase in the degree of plastic deformation of the as-cast Haynes 282 and the samples produced by the DMLS technique resulted in an increase in the strength of the tested samples, with reduced ductility.

Effect of annealing on the microstructure and properties of IN 625 specimens manufactured by selective laser melting

The study examines the effect of the annealing on the microstructure, tensile strength (small flat dog-bone specimen size with 5 mm dimension of measuring base) and corrosion resistance of IN 625 nickel superalloy specimens manufactured by means of selective laser melting method (SLM). The annealing of such specimens was carried out in a chamber furnace in a protective atmosphere of argon at a temperature of 1038 °C for 1 h. The cooling process was carried out in an atmosphere of air at ambient temperature. The microstructure of the IN 625 nickel superalloy after the 3D printing process and after the post-process heat treatment (HT) was examined by means of scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed a uniform microstructure after the SLM process with element microsegregation. The cooling rate in the heat treatment was not sufficient which caused precipitation at the grain boundaries, most probably carbides and resulted in only a partial increase in ductility much lower than that of the material in initial state despite the high temperature applied during the annealing. The strength in the HT was on a level comparable to as-build state, 852 MPa and 891 MPa, respectively. Additional corrosion resistance tests were performed by the potentiodynamic method in a 3.5% NaCl solution at room temperature. HT increased the current density variation from ipass due to the formed precipitates. Our studies show that the size effect is an important factor when assessing the properties of IN 625 obtained using SLM. Despite similar microstructure, the structure defects play a more significant role which translates into lower mechanical properties than in normal sized specimens defined by the standard ASTM E8.

Computation and experimental analysis of the resistance of superalloys to low cycle deformations

Diagrams of cyclic elastoplastic deformation in a general case characterize the resistance of a material to a low cycle loading and display a relation between current values of stresses and strains during deformation process. Those diagrams in the mechanics of deformation and fracture are described by rather complicated state equations with a nonlinear dependence on conditions and modes of loading including temperature, deformation rate, cycle form, type of the stress state, absolute size of sections, working medium, type of constructional material, etc. The entity of aforementioned factors affects a shape of the deformation curve (diagram) of the material and key parameters of the corresponding state equations, including basic characteristics of the mechanical properties, i.e., the elasticity module, yield point and ultimate stress, indicators of static and cyclic hardening. Experimental data on the kinetics of cyclic and one-way accumulated plastic strains in each loading half-cycle (cycle) obtained in static and low cycle tests of nickel superalloy specimens revealed that change in deformation characteristics exhibit a drastically nonlinear character in conditions of cyclic elastoplastic strain which is described on the basis of power equations and corresponding parameters of cyclic deformation diagrams. The parameters of those equations depend on the type of cyclically hardening/softening or stable material under deformation of the material in elastoplastic region. It is noted that resistance of materials to cyclic elastic-plastic strain can be described by a set of analytical expressions containing a kinetic function (which changes with number of loading half-cycles) in the form of power or exponential expressions depending on the cyclic properties and characteristics of the mechanical properties of the specific structural material. The obtained calculated and experimental data on the kinetics of strain of the alloy under study in conditions of cyclic elastoplastic loading, as well as on the parameters of the strain diagram (which are basic characteristics for the corresponding state equations) provide the possibility to take full advantage of using the deformation-kinetic criteria of damage accumulation under considered loading conditions to calculate the fatigue life of the structural elements manufactured from the alloy and operated, as a rule, under severe temperature and heavy-loaded conditions. The results of the experiments and calculations are given in the form of diagrams of cycle-by-cycle kinetics of the cyclic and accumulated plastic strains of the material for the soft and hard modes of loading in a wide range of test temperatures.

Experimental confirmation of high-temperature phase boundaries in the nickel-rich part of Ni-Al-Cr system

Precise determination of the course of phase boundaries is particularly important for alloys operating at elevated temperatures. In the case of multi-component materials such as nickel superalloys, computational methods are often used for this purpose. They are based on binary and ternary systems and require reliable experimental data. Commonly used research methods for determining phase boundaries at elevated temperature have a number of limitations and it is difficult to interpret their results without the support of other studies. This work presents a series of experiments to confirm the course of phase boundaries γ′/(γ′ + γ) and (γ′ + γ)/γ in Ni-Al-Cr system, particularly at 600 °C. For this purpose, a series of alloys from Ni-rich part of Ni–Al-Cr ternary system was prepared by vacuum induction melting (VIM) and casting into graphite mold under an argon protective atmosphere. Samples after machining were subjected to compression tests using the Gleeble 3800 thermomechanical simulator at room temperature as well as directly at 600 °C after pre-heating at 1100 °C. Stress–strain curves of various character were obtained and were associated with the appropriate phase structure confirmed by X-ray diffraction (XRD) analysis. The relationship between the phase structure of the studied alloys and their mechanical properties has been proven. Compression results were compared with the results of hardness measurements, high-temperature calorimetric solution method and differential thermal analysis (DTA). The obtained results showed a very good agreement in terms of the course of the γ′/(γ′ + γ) and (γ′ + γ)/γ phase boundary in Ni-Al-Cr system.

Isothermal oxidation resistance and microstructure evolution of VPS-TiAlCrY coating on TiAl single crystals at 1100–1200 °C

TiAlCrY coating was fabricated on TiAl single crystals by vacuum plasma spray (VPS) technique to investigate the oxidation resistance and microstructure evolution via isothermal oxidation tests at 1100 and 1200 ℃, respectively. The results indicated that the oxidation resistance of TiAlCrY coating was excellent with the maximum spallation degree of oxide layer extremely below the critical value of coating failure. The oxide growth kinetic curves of the TiAlCrY coating complied well with parabolic law, and the oxidation rate constants were comparable to those of typical MCrAlY coatings on nickel superalloys. In particular, the strong α-Al2O3 formation ability in the initial oxidation process and the great chemical compatibility at coating-substrate interface contributed to the durable oxidation resistance of TiAlCrY coating. This work highlights the potential application of VPS-TiAlCrY coating for TiAl single crystals at 1100–1200 ℃.

Tool Wear Characterization in Turning of a Nickel Superalloy Through Customized Pin-On-Disk Tests and Acoustic Emission Signals Analysis

Abstract Wear mechanisms taking place during machining strongly affect the overall process reliability, product quality, and production costs. It is necessary to have useful monitoring techniques for monitoring the wear trend during the process and to identify wearing phenomena occurring during the evolution of the process. In order to get a reliable tool, it is necessary to identify and distinguish the contributing factors and wear mechanisms happening during machining. In this paper, an acoustic emission sensor has been used to identify characteristic features pertaining different wear mechanism displayed during turning of waspaloy. The methodology used to distinguish the contributing elements was developed coupling turning tests with corresponding tribological experiments so that clear evidences on different contributions were identified showing a useful tool for industrial and research applications.

High temperature corrosion-fatigue behavior of a shot peened nickel based superalloy

As turbine entry temperatures (TET) in modern gas turbine engines continue to increase, Type II hot corrosion has the potential to be a significant damage mechanism at turbine disk rims as temperatures approach 700 °C. Therefore, assessment of the effect of hot corrosion damage is essential. In the current research, low cycle corrosion-fatigue behavior of a newly developed polycrystalline nickel superalloy was investigated. The testing program involved consideration of the variations in fatigue life brought about by changes in surface condition when tested at 700 °C in a representative service environment. The high temperature corrosion-fatigue resistance behavior is compared with a previous generation alloy, and detailed fractography to identify the mechanisms of fatigue crack initiation is discussed. High temperature corrosion-fatigue behavior is also correlated to the shot peened work hardened layer.

High‐Temperature Creep Properties of an Additively Manufactured Y2O3 Oxide Dispersion‐Strengthened Ni–Cr–Al–Ti γ/γ’ Superalloy

The effects of the modification of a high‐γ' Ni–8.5Cr–5.5Al–1Ti (wt%) model superalloy with 0.5 wt% Y2O3, manufactured by laser powder bed fusion, on the microstructure and compressive creep resistance, are investigated. Compared with the base alloy, the oxide dispersion‐strengthened (ODS) alloy exhibits 8–10 times slower creep rates at 800 °C, over a wide range of compressive stresses (35–250 MPa). Two creep regimes are observed: diffusional creep, hypothesized to be due to grain boundary sliding, and dislocation creep, with stress exponents n of 2 and 5, respectively. Compared with the horizontal direction, the vertical build direction is characterized by lower creep rates, due to the vertically elongated grain structure. Nonetheless, the ODS alloy's weakest (horizontal) direction shows better creep resistance than the non‐ODS alloy in its strongest (vertical) direction, despite a higher number of as‐built defects (slag, cracks) in the ODS alloy. The strengthening potential of ODS modification of additively manufactured nickel‐based superalloys is thus demonstrated. The development of successful commercial ODS nickel superalloys for additive manufacturing processing requires further additions of grain boundary strengthening elements as the dispersoids do not significantly increase the grain boundary strength, as their cracking is prevalent in the ODS alloy.

Deformation mechanisms of additively manufactured Hastelloy-X: A neutron diffraction experiment and crystal plasticity finite element modeling

The development of strong textures can affect mechanical anisotropy in the specimens produced by the laser powder bed fusion (LPBF) additive manufacturing (AM) technique. In this study, in-situ neutron diffraction experiments were conducted on nickel superalloy specimens to understand how mechanical ansitropy and the evolution of internal strains are affected by changing the LPBF-AM parameters. In addition, Electron Backscatter Diffraction (EBSD) measurements were performed to characterize the initial microstructure of the specimens. The measured EBSD maps were imported into a crystal plasticity finite element (CPFE) model to further study how different AM parameters, specifically laser power and scanning speed, affect the development of internal strains. At higher specific energy (SE) inputs, columnar grains are observed, and samples developed a 〈110〉 texture along the building direction and a 〈100〉 texture along the scanning direction, while at lower SEs random texture is observed. The development of texture affects elastic and plastic anisotropy, as well as the development of internal strains in different directions, particularly for the {200} lattice strains measured in the laser scanning direction. It is shown that (111) 〈110〉 slip system is the most active one for the range of applied strains.

The Effect of Selected Process Conditions on Microstructure Evolution of the Vacuum Brazed Joints of Hastelloy X Nickel Superalloy Sheets

The Effect of Selected Process Conditions on Microstructure Evolution of the Vacuum Brazed Joints of Hastelloy X Nickel Superalloy Sheets

Compositional Glass: A State with Inherent Chemical Disorder, Exemplified by Ti-rich Ni3(Al,Ti)1 D024 Phase

A compositional glass is a state with an unavoidable disorder in chemical compositions on each site, characterized by frustration and freezing of the compositional degrees of freedom at low temperature. From this state a full atomic long-range order is unachievable by a reasonable thermodynamic treatment. There is a similarity between a spin glass (a magnetic state with disorder in spin orientations) and a compositional glass (with disorder in site occupations by chemical elements): both have frustrated ground states and a frozen disorder at low temperatures T < Tf (here Tf is called the freezing temperature). While it is possible to perform a ground-state search in a compositional glass, the resulting set of the fully ordered structures does not adequately represent the real solid with an inherent atomic disorder. Compositional glasses constitute a class of materials, which is insufficiently understood, but is of high industrial importance. Some of the phases in the precipitated alloys (including steels, high-entropy alloys, and superalloys) might be compositional glasses, and their better understanding would facilitate materials design. Due to their strength at high operating temperatures, superalloys are used in combustion engines and particularly in jet turbine engines. Precipitation strengthening of nickel superalloys is an area of active research. Local phase transformations inside Ni3Al-based precipitates are of particular interest due to their impact on creep strength. In the Ni3(Al1−xTix)1 ternary system, the competing phases are Ni3Al-type L12 (γʹ) and Ni3Ti-type D024 (η), while D019 (χ) is higher in energy. These three phases differ by the stacking of atomic layers: locally, the last two look like the internal and external stacking faults in L12. We compute enthalpies of disordered and ordered Ni3(Al1−xTix)1 ternary structures, examine phase stability, investigate the ground states and competing structures, and predict that the Ti-rich Ni3(Al1−xTix)1 D024 phase is a compositional glass with the atomic disorder on the Al/Ti sublattice. To resolve apparent contradictions among the previous experiments and to confirm our prediction, we perform X-ray diffraction and scanning electron microscopy analysis of the cast Ni3(Ti0.917Al0.083)1 sample. Our measurements appear to confirm the ab initio computed results. Our results elucidate properties of compositional glasses and provide a better understanding of precipitation strengthening mechanisms in Ni superalloys.

Enhanced High-Temperature Mechanical Behavior of an in Situ TiAl Matrix Composite Reinforced With Alumina

A Ti-45Al-3Cr-2.5Nb alloy reinforced with in situ formed alumina has been produced by means of centrifugal casting by adding zirconium oxide in the crucible. The dispersion-strengthened alloy has been characterized to verify its microstructure and particle distribution. Mechanical tests carried out over the temperature range 850–950 °C highlighted that in situ formed alumina allows to increase the alloy yield stress by 21% at 850 °C and by 35% at 900 °C. Moreover, the in situ formed oxide particles produced an increase of the Young’s modulus of about 10% at 850 °C and of about 8% at 900 °C. Considering that the tested alloy has a density that is about a half of nickel superalloys, obtaining high specific mechanical properties over the temperature range 850–950 °C can boost its application in the production of turbine blades.Graphical abstract

RESEARCH AND OPTIMIZATION OF REFURBISHMENT OF HPT BLADES OF THE D-18T AIRCRAFT GAS TURBINE ENGINE BY MICRO-PLASMA POWDER WELDING

In current work, peculiarities of the micro-plasma powder welding deposition process applied to the batch refurbishment of D-18T aircraft engine HPT blades made of ZhS32-VI nickel superalloy with limited weldability have been studied. It has been demonstrated that extending operating resource over 6-8 thousand hours leads to an increase in ZhS32-VI “base-deposited metal” weld’s cracking susceptibility during welding and subsequent thermal processing operations. It has been shown that providing stable forming of deposited bead on the shroud edge’s surface requires applying nonstationary impulse modes of straight polarity welding current. Considering the significant amount of technological parameters of the process studied, subjective analysis of such welding modes is extremely complicated. We have introduced the method of specifying requirements for such single-layer micro-plasma powder welding deposition modes with welding current in a range of 7-20 A according to the criteria of effective arc heating power and heat input, which involves using the system for registration and digital processing of welding current-welding bead deposition time dependency. Based on the analysis of statistical data on the quantitative evaluation of cracking susceptibility of the investigated weld, the optimal range of average values has been discovered for these generalized welding deposition mode parameters to be applied in a manual or automated process, which provides no more than several percent of cracked blades detected at the end of refurbishment technological cycle. We have shown that significant technological parameters, which affect the amount of technological defects during mentioned blades’ refurbishment, are the average value of effective welding current and ZhS32 superalloy powder quality, primarily determined by oxygen and nitrogen average weight content in its dispersed particles. It was also shown that the increase in average weight content of gas impurities in the filler powder, primarily oxygen, causes a significant increase in energy consumed on deposited bead formation during the micro-plasma powder deposition process. An initial quality control method for the ZhS32-VI filler powder range has been proposed. The method is based on the average weight content of oxygen and nitrogen, evaluated by reducing fusion in transporting gas flow and on evaluation criteria of effective arc heating power and heat input average values of witness sample blades’ refurbishment process and their conformity to previously defined optimal. An evaluation of future application possibilities for registration systems and deposition mode analysis in batch repair conditions of nickel superalloy aircraft parts has been introduced.

Electroless Deposition of Nickel-Phosphorus Composite Layer with Incorporated Amorph Boron Particles and Subsequent Heat Treatment for the Formation of Nickelboride

In an effort to decrease the operating cost in the manufacturing industries, industrial knives and large tools in the forming technology should possess characteristics that increase its lifetime. One such properties would be the high surface hardness and a possibility to improve this characteristic would be through boriding. Through this method, whereby boron powder or paste is spread on the tool surface before the workpiece is heated in the oven at 750 – 950 °C for 4 – 6 h, a diffusion process occurs between the boron paste and the substrate. Borides are formed in the workpiece until a depth of approx. 250 µm from the workpiece surface depending on the substrate type and the heat treatment parameters. Genel et al. attained a hardness value of around 1700 HV at 75 µm depth when they borided AISI W1 steel workpiece at 950 °C for 6h[1],[2],[3]. By boriding a nickel superalloy, Inconel 718, at 950°C for 6h, Campos-Silva et al. achieved approx. 2200 HV at 30 µm depth[4]. However this method is disadvantageous in terms of the high energy cost and the long treatment period.As an alternative, hard chrome layer that has a hardness value between 600 to 1200 HV[5],[6] can be electroplated on the workpiece. Besides having an improved wear protection, this chrome layer offers a good corrosion protection and can be produced with a lower cost since it does not need a thermal post-treatment to increase its hardness and hence this method is less energy intensive as boriding. Admittedly the application of chrome-VI ions in the hard chrome electrolyte is without special permission prohibited in the European Union since 2017 according to REACH[7] considering its carcinogenic properties[8],[9],[10]. Another possible method would be through composite coating. Many works have been done on electroless composite nickel coating with boron nitride, silicium carbide, diamonds, aluminium oxide and titanium oxide among others used as dispersoid. After a heat treatment at 400 °C for 1 h, the hardness of most of these coating increases significantly from around 700 HV to approx. 1100 HV[11].In the present study, the positive aspects of boriding and electroless deposition of nickel-phosphorus layer should be combined, so that a hard surface with a good wear resistant can be produced for industrial tools in a more efficient way. It is expected that lower heat treatment temperature and/or less treatment time is needed to achieve the same effect as boriding since boron particles are already homogenously distributed and have a shorter diffusion path in the thick composite layer. In addition to that, the hardness gradient throughout the heat-treated composite nickel coating should be much lower compared to boriding, especially when a high amount of boron particles is evenly distributed in the layer. The coating thickness, which will then be equated as boride layer thickness after sufficient heat treatment, can be manipulated with coating parameters and electrolyte type. Hence, through this combined method, a thicker boride layer is achievable by depositing a thicker composite nickel layer.Amorph boron powder of different sizes are used as dispersoid in the composite electroless nickel layer. The dependency of incorporated boron content in the composite layer with the particle content in the electrolyte, the particle size and the effect of ultrasound-assisted deposition is investigated. A homogenous particle distribution in the deposited layer and controllable incorporation of the boron particle in the nickel-phosphorus matrix are desirable. Furthermore, the agglomeration behaviour of the boron particle in the electrolyte is examined through laser doppler electrophoresis. The influence of the incorporated boron particle on the coating hardness and its wear resistance before and after heat treatment is studied by measuring it according to Vickers and with Calotester kaloMAX NT II. The effect of the heat treatment parameters with respect to the heat-treating temperature and time to the surface hardness and its wear resistance is investigated. At the conference results of the metallographic examinations, SEM-EDS and XRD analysis will be presented. Figure 1

Stable nitride precipitation in additively manufactured nickel superalloys

With negligible quantities of nitrogen, wrought and welded solid solution strengthened nickel superalloys usually contain carbides and topologically close-packed phases, such as Laves phase. However, appreciable nitrogen levels on the order of 0.1 % mass fraction drove the precipitation of a range of unanticipated nitride phases in additively manufactured Inconel 625 in the as-deposited and post process hot isostatically pressed conditions. Different nitride phases were observed with small changes in alloy chemistry. Cubic metal nitrides (MN), tetragonal Z-phase (CrNbN), and diamond-cubic metal η-nitrides (M 6 N) were found within the γ matrix of Inconel 625 containing relatively low Fe (1 %), low Ti (0.02 %), and high Si (0.39 %) mass fractions. Conversely, these phases were replaced by only MN nitrides in a similar Inconel 625 alloy with elevated mass fractions of Ti (0.21 %) and Fe (4 %). These various phases, however, were not fully predicted using state-of-the-art computational thermodynamic tools and databases, indicating a sparsity of data for nickel superalloys. Even after hot isostatic pressing, many nitrides persisted and only experienced slight changes in composition and lattice parameters in both materials. The stability of these nitride phases presents a potential pathway for achieving enhanced high temperature and creep properties within this and similar alloy systems. • Significant nitrogen contents are measured in Inconel 625 powder. • Only nitrides (MN, Z-phase, η-nitride) are observed in two as-deposited Inconel 625 alloys. • Minor alloying elements influence the type of nitride that forms. • Most nitrides persisted after post-process hot isostatic pressing.

Advanced time-resolved characterization of Stress Assisted Grain Boundary Oxidation of 718 Ni superalloy

Nickel superalloys are used for harsh condition application cases as they have high chemo-thermomechanical stability. However, they can suffer from embrittlement due to stress corrosion cracking. This effect is difficult to observe as it can take place at long time scales. Here we propose a feasible experiment to study stress assisted grain boundary oxidation, a phenomenon that has similar mechanisms involved that can take place in laboratory compatible time scales. We observed the event using phase and diffraction contrast tomography while applying monotonic loading of the sample at 650 °C. This initial analysis shows that the experimental setup is a good candidate for the study of such degradation mechanism.

Investigation of evaluated temperature oxidation for IN-738 LC superalloy turbine blade thermally coated by AL2O3 using slurry coating process

The study aims to investigate the effect of Al2O3 and Al additions to Nickel-base superalloys as a coating layer on oxidation resistance, and structural behavior of nickel superalloys such as IN 738 LC. Nickel-base superalloys are popular as base materials for hot components in industrial gas turbines such as blades due to their superior mechanical performance and high-temperature oxidation resistance, but the combustion gases' existence generates hot oxidation at high temperatures for long durations of time, resulting in corrosion of turbine blades which lead to massive economic losses. Turbine blades used in Iraqi electrical gas power stations require costly maintenance using traditional processes regularly. These blades are made of nickel superalloys such as IN 738 LC(Inconel 738). Few scientists investigated the impact of Al2O3 or Al additions to Nickel-base superalloys as coating layer by using the slurry coating method on oxidation resistance to enhance the Nickel-base superalloy's oxidation resistance. In this study, IN 738 LC is coated with two different coating percentages, the first being (10 Al+90 Al2O3) and the second being (40 Al+60 Al2O3). Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) were performed on all samples before and after oxidation. According to the results, SEM images of the surface revealed that the layer of the surface has a relatively moderated porosity value and that some of the coating layers contain micro-cracks. The best surface roughness of specimens coated with 60 % alumina+40 % aluminum was 5.752 nm. Whereas, the surface roughness of specimens coated with 90 % alumina+10 % aluminum was 6.367 nm.Results reveal that alloys with both Al2O3 and Al additions have reported a positive synergistic effect of the Al2O3and Al additions on oxidation resistance. Moreover,the NiCrAl2O3 thermal coating has good oxidation resistance and the effective temperature of anti-oxidation is raised to 1100 °C in turn reducing the maintenance period of turbine blades

Enhancing the Oxidation Behavior of Zr-Modified Aluminide Coatings on Inconel 600 at Different Temperatures

In the recent search nickel superalloy Inconel 600 was coated with Zr-modified aluminide diffusion coating using pack cementation technique. Diffusion coating was done in a single step utilizing a conversion reaction of 10% Al, 2% ZrO2, 4% NaCl, and 84 percent Al2O3 (wt. percent ) and a simultaneous aluminizing-zirconizing process. The diffusion coating operations were performed in an argon environment at 1050 °C for 10 hours. The test of the isothermal oxidation in dry air was performed on the Inconel Alloy 600 (IA600) without and with Zr-modified aluminide coating for 800-1000 °C. The oxidation kinetic of IA600 and its coated system was found to follow the parabolic law. The activation energy is 243 kJ/mol. for the coated system and 457 kJ/mol. for the uncoated system. XRD analysis show that oxide phases are formed on an uncoated IA600 surface during most of the oxidation exposure conditions are NiO, Cr2O3, Fe2O3, NiCr2O4 and NiFe2O4, , whereas alumina scale is the major oxide that is obtained on the surface of coated samples.