Behavior Of Nickel-based Superalloy Research Articles

Cyclic Behavior of Nickel-Based Superalloy 617 M at Elevated Temperature

Cyclic Behavior of Nickel-Based Superalloy 617 M at Elevated Temperature

Effect of contact temperature, normal load and dry sliding velocity on the coefficient of friction and wear behavior of nickel based super alloy

PurposeThe purpose of the present paper aims to, study the coefficient of friction and wear behavior of nickel based super alloys used in manufacturing of gas and steam turbine blades. In present paper, parametric study focuses on normal load, dry sliding velocity and contact temperature influence on coefficient of friction and wear of a nickel based super alloy material.Design/methodology/approachExperimental investigation is carried out to know the effect of varying load at constant sliding velocity and varying sliding velocity at constant load on coefficient of friction and wear behavior of nickel based super alloy material. The experiments are carried out on a nickel based super alloy material using pin on disk apparatus by load ranging from 30 N to 90 N and sliding velocity from 1.34 m/s to 2.67 m/s. The contact temperature between pin and disk is measured using K-type thermocouple for all test conditions to know effect of contact temperature on coefficient of friction and wear behavior of nickel based super alloy material. Analytical calculations are carried out to find wear rate and wear coefficient of the test specimen and are compared with experimental results for validation of experimental setup. Regression equations are generated from experimental results to estimate coefficient of friction and wear in the range of test conditions.FindingsFrom the experimental results, it is observed that by increasing the normal load or sliding velocity, the contact temperature between the pin and disk increases, the coefficient of friction decreases and wear increases. Analysis of variance (ANOVA) is used to study the influence of individual parameters like normal load, dry sliding speed and sliding distance on the coefficient of friction and wear of nickel based super alloy material.Originality/valueThis is the first time to study effect of contact temperature on the coefficient of friction and wear behavior of nickel-based super alloy used for gas and steam turbine blades. Separate regression equations have been developed to determine the coefficient of friction and wear for the entire range of speed of gas turbine blades made of nickel based super alloy. The regression equations are also validated against experimental results.

Deformation Behavior of Nickel-Based Superalloy Predicted by Spherical Representative Volume Element Approach

Deformation Behavior of Nickel-Based Superalloy Predicted by Spherical Representative Volume Element Approach

Investigation on electric erosion behavior of nickel-based super alloy (Waspaloy: Ni, Cr, Co, Mo, Ti, Al) using response surface methodology

Waspaloy is one of the nickel-based alloys and its application is mostly positioned in the aerospace industry owing to its strength retaining capacity at higher temperature, better corrosion resistance, and toughness. Multi-response optimization technique, response surface methodology (RSM) was adopted to optimize the electrical discharge machining parameters during machining of Waspaloy. Various control factors such as peak current, voltage, duty cycle, and flushing pressure were selected with three levels. The material removal rate (MRR) and surface roughness (SR) were selected as response parameters for investigating the machining characteristics. A central composite design with five center points was used for experimental design. The best optimal set of control parameters were identified for the higher MRR and lower Sr The experiments have been validated by using analysis of variance and a confirmation test was conducted. From RSM, the optimum machining conditions for drilling the hole, namely, voltage: 125 V, flushing pressure: 0.8 kg cm−2, and peak current: 22 A and duty cycle of 20% have been identified. Further, this investigation highlights the formation and the effect of the recast layer by using scanning electron microscopy.

Corrosion Behavior Studies and Parameter Optimization of Dissimilar Alloys Joined by Electron Beam Welding

A number of special alloys are used in harsh environments with extreme high temperatures due to their superior properties like good oxidation and creep resistance. Over the past few years, joining of dissimilar alloys using electron beam welding (EBW) has been of prime importance owing to its superior advantages. The related work primarily involves joining dissimilar alloys using special features like controlling location and beam size and promises less heat affected zone. The current research is focused on investigating the parameters of EBW on corrosion behavior of nickel-based super alloy and stainless steel. In order to optimize the number of experiments to be performed, Taguchi method is used. The weld joints are prepared as per the parametric design and potentiodynamic polarization studies have been carried out on the weldments in 5% NaCl environment in order to assess the corrosion behavior of welded materials.

Investigation on Work Hardening Behavior of Nickel-Base Superalloy during Hot Working Process by EBSD

The Nickel-base superalloy samples were prepared by the isothermal forging in strain rate 1s-1 at deformation temperature 1070°C with different strain levels. The EBSD was carried out in order to investigate the microstructural changes that took place due to strain level. The result is the samples has no apparent dynamic recrystallization behavior in hot deformation in 1s-1 at 1070°C. The true stress-true strain curve has two peak values in the strain level of 20% and 60%, and one valley value in the strain level of 50%. The first peak value is result in the activation of slip system and the beginning of recrystallization and the second peak value of the true stress-true strain curve is result in the inhibition of activation of slip system and grain growth by the dislocation density. The work hardening behavior of P/M Nickel-base superalloy may be related to the size ratio of γ’ phase with grain size.

Effect of Microstructure on High-Temperature Mechanical Behavior of Nickel-Base Superalloys for Turbine Disc Applications

The objective of this work was to establish relationships between alloy microstructure and high temperature mechanical properties such as strength, creep, and creep crack growth in Nickel-base powder metallurgy superalloys. Systematic variations of super solvus heat-treatments generated test material from three next-generation turbine disc alloys. Quantification of key microstructural features such as γ’ distribution and morphology and grain boundary serrations was coupled with mechanical testing results in order to optimize microstructure for operating conditions specific to the bore region.

Use of instrumented micro-indentation to study the mesoscopic elasto-plastic behavior of GH4145/SQ superalloy during high-temperature cyclic straining

In this paper the instrumented micro-indentation testing (IIT) was used to study the mesoscopic elasto-plastic behavior of nickel-base superalloy GH4145/SQ subjected to cyclic straining at an elevated-temperature. For this purpose, a series of experiments including high-temperature low-cycle fatigue tests, instrumented micro-indentation measurements and OM (TEM) examinations were carried out. The characteristic parameters of indentation (C, hmax, S, hr, We and WP) during high-temperature fatigue failure process were determined from the experimental indentation load–depth (P–h) curves. The fatigue mesoscopic elasto-plastic properties such as E, σy and n were estimated using Dao et al.’s analysis algorithm [19], combined with the indentation characteristic parameters, and their distribution patterns were verified in a statistical sense. Microstructural examinations using both OM and TEM were performed to provide the micromechanisms for the fatigue mesoscopic elasto-plastic behavior of the superalloy during high-temperature low-cycle fatigue.

Modelling Nimonic 80A rheological behaviour through artificial neural networks

In this paper neural networks are utilized to represent the rheological behaviour of nickel-base superalloys under hot forging conditions. A feedforward back-propagation neural network has been trained and tested on rheological data, obtained from hot compression experiments, performed under single- and multi-step deformation conditions, both at constant and varying strain rates. The good agreement between experimental and calculated flow curves shows that a properly trained neural network can be successfully employed in representing a material response to hot forging cycles.

Creep crack growth simulations by a modified damage model

Researchers have proven that both environmental effects and the formation of defects such as cavities due to plastic flow and creep control the high temperature fracture behavior of nickel base superalloys under quasi-static load. Creep crack growth experiments are well suited to investigate these effects. Modeling of such tests can help to better understand the occurring mechanisms. Waspaloy is an example for a material with numerous cavities ahead of the crack tip after creep crack growth testing at 973 K. In this case, the model must be able to combine damage caused by plastic and viscoplastic flow. The complicated stress state caused by the geometry, the crack propagation and the material’s behavior require the use of FEM to predict creep crack growth. Thus, several modifications to the classic damage models become necessary. Independent uniaxial creep tests provide the required model parameters. However, the stress state at a crack tip is multiaxial. Therefore, the parameters describing the interdependence between the hydrostatic pressure and the damage evolution must be determined separately. One single creep crack growth test is used for their determination. An application of the developed model to creep crack growth produces a good consistency with the experimental data. Some details of the tests which could not be explained before are now better understood. For example, the calculations indicate a pre-damage in the specimen which may be produced by inserting the pre-crack and by preparing the specimen. Taking into account all these facts, damage evolution due to ductile deformation is probably the decisive mechanism in the investigated case. The results also support the assumed dependency of damage on the hydrostatic pressure.

Characterization of Single Crystal Superalloy SC16 by Small Angle Neutron Scattering and Complementary Analytical Techniques

At the Hahn-Meitner-Institut, Berlin in a comprehensive research program to study the influence of the microstructure on the behavior of nickel-base superalloys, the authors characterize the microstructure of a single crystal alloy SC16 after different heat treatments and deformations. The alloy SC16 (16% Cr, 3% Mo, 3.5% Ti, 3.5% Al, 3.5% Ta, rest Ni; in weight percentage) was recently developed for applications in land-based gas turbines and contain about 40% volume fraction of {gamma}{prime} precipitates. SC16 has high chromium additions, which partitions strongly in the matrix. The TCP phases are known to precipitate from over saturated matrix, especially in high chromium bearing alloys. For this reason the composition of SC16 was optimized using the PHACOMP calculations and so far no TCP phases have been reported in this alloy after short time heat treatments. In the present study to characterize the {gamma}{prime} morphology in SC16 after various heat treatments by small angle neutron scattering (SANS), the authors observe strong streaking along and sometimes along directions in the two dimensional scattered intensity profiles. The analysis of the SANS data and characterization using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicate that the streaksmore » result from plate-like precipitates, which occupy very small volume fraction.« less

A correction to optimum alloy composition for design of high-temperature high-strength Al [sbnd]Ti [sbnd]V [sbnd]Zr alloys through thermodynamic calculations

It is very likely that high-strength Al-base alloys up to 698K can be developed in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. According to a review paper by Adam, several Al-base systems containing transition metal elements for potential elevated temperature use were suggested based on low values of diffusivities and solubilities. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al{sub 3}(Ti,V). Much of titanium and vanadium can be substituted for zirconium in the DO{sub 23}-type Al{sub 3}Zr compound, creating Al{sub 3}(Ti,Zr) and Al{sub 3}(V,Zr), respectively. It was of interest to design the Al-Ti-V-Zr system and optimize the compositions of added transition elements to minimize the lattice mismatch, and thus an interfacial energy, and maximize the strengthening effects at high temperatures. The authors were able to do experiments on phase stabilities of Al{sub 3}Ti-Al{sub 3}V-Al{sub 3}Zr system and revise the thermodynamic parameters of this system. Therefore, this study reports onmore » the new optimum alloy composition which is supposed to maximize the coarsening resistance of the strengthening Al{sub 3}(Ti,V,Zr) phase at high temperatures of service in this system.« less

Nickel-base superalloys: current status and potential

The evolution of nickel-base superalloys has occurred over about 50 years through a combination of alloy and processing developments to satisfy quite different service requirements of various components of the gas turbine. There is now a good general understanding of the mechanisms leading to the unusual mechanical properties of these precipitation strengthened materials. Although the scope for further significant improvements in the behaviour of nickel-base superalloys appears to be limited, it is unlikely that their full potential is yet being achieved in engineering applications. Progress towards the development and validation of constitutive laws describing fully anisotropic deformation is described.

Lattice misfit variation of Al 3(Ti,V,Zr) in Al  Ti  V  Zr alloys

It seems likely that high-strength Al-base alloys useful up to 698K can be developed in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. An additional factor to be considered is the stability of the hardening phase with respect to Ostwald ripening. This coarsening resistance is necessary so that the required strength level can be maintained after the long-time service at high temperatures. A good lattice matching between the intermetallic compound and the aluminum matrix is necessary to promote a low interfacial energy and thus, a low driving force for particle coarsening. In this paper, several Al-base systems containing transition metal elements for potential elevated temperature use were suggested based on low values of diffusivities and solubilities. The equilibrium crystal structures of Al{sub 3}Ti, Al{sub 3}V and Al{sub 3}Zr are tetragonal DO{sub 22}, DO{sub 22} and DO{sub 23}, respectively. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al{sub 3}(Ti, V). Muchmore » of titanium and vanadium can be substituted for zirconium in the DO{sub 23}-type Al{sub 3}Zr compound, creating Al{sub 3}(Ti, Zr) and Al{sub 3}(V, Zr), respectively.« less

Design of high-temperature high-strength AlTiVZr alloys

This paper reports that it seems plausible to develop high-strength Al-base alloys useful up to 698K in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. An additional factor to be considered is the stability of the hardening phase with respect to Ostwald ripening. This coarsening resistance is necessary so that the required strength level can be maintained after the long-time service at high temperatures. The equilibrium crystal structures of Al{sub 3}Ti, Al{sub 3}V and Al{sub 3}Zr are tetragonal D0{sub 22}, D0{sub 22} and D0{sub 23}, respectively. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al{sub 3}(Ti, V). Much of titanium and vanadium can be substituted for zirconium in the D0{sub 23}- type Al{sub 3}Zr compound, creating Al{sub 3}(Ti, Zr) and Al{sub 3}(V, Zr), respectively. In particular, it has been reported that fcc L1{sub 2}-structured Al{sub 3}M dispersoids form in the rapidly solidified Al-V-Zr and Al-Ti-Zr systems and both L1{sub 2}more » and D0{sub 23}-structured Al{sub 3}M phases showed slow coarsening kinetics.« less