Turbine Engine Blades Research Articles

Design and Analysis of Alternative Coating Bio-Material for Gas Turbine Engine Blade for High Temperature Aerospace Application

Design and Analysis of Alternative Coating Bio-Material for Gas Turbine Engine Blade for High Temperature Aerospace Application

Vacuum plasma erosion resistant 2D nanocomposite coating Avinit for compressor blades of gas turbine engines of aircraft engines

The work is devoted to the search for new vacuum-plasma coatings with high hardness to increase the durability of the compressor blades of the GTE of aircraft engines Ti-Al-N-based vacuum-plasma coatings obtained by Avinit technologies, which ensure the application of hard, high-quality coatings with dramatically reduced micro-arc damage, were selected as candidates. Avinit multilayer coatings have higher functional characteristics than TiN (microhardness, crack resistance, temperature resistance, erosion and corrosion resistance) and may be promising for applying erosion-resistant coatings for compressor blades. Avinit technologies are technologically closest to the vacuum-plasma technologies used in industrial production for applying TiN protective coatings. New multi-layered 2D nanocomposite wear-resistant ion-plasma hard coatings Avinit (TiN-AlN)n have been developed. The created software products made it possible to reach a qualitatively new level in terms of further modification and improvement of the designs of Avinit functional coatings, stability of technologies and improvement of their quality control when applying such coatings for use in the production of compressor blades of gas turbine engines of aircraft engines. Special attention is paid to methods of preliminary ion-plasma treatment of surfaces before coating. Metallographic studies of the chemical and phase composition and structure of Avinit (TiN-AlN)n coatings have been carried out. The thickness of the coatings is 7-9 μm, the microhardness is 34-35 GPa (compared to the serially used TiN coating: 27.4 GPa). The use of three-stage ion-plasma treatment in Avinit technologies using a double vacuum-arc discharge followed by the application of strengthening coatings in a single technological cycle eliminates the formation of cracks and ensures the production of tightly bonded, high-quality coatings of a given composition with the maximally reduced share of the droplet component. The developed coatings (TiN-AlN)n were applied to experimental batches of working compressor blades of GTE aircraft engines for bench tests.

STUDY OF NANOMODIFICATION OF NICKEL ALLOY GS3 WITH TITANIUM CARBIDE

The work deals with the fundamentals of nanomodification of the GS3 heat-resisting multicomponent nickel alloy, out of which blades for gas turbine engines are made. The selection of the modifier for the experimental alloy was justified; the technology of acquiring the nanomodifier, using the plasma-chemical synthesis method, was developed; and the calculations of the specific surface of the TiC particles were performed. The required quantity of nanomodifier introduced to the liquid alloy to acquire the set structure was determined experimentally. Through electronic microprobe analysis, introduction to the metal matric of nanoparticles of titanium carbide is approved. Nanomodification allows achieving refinement of the GS3 nickel alloy structure, which is going to provide an opportunity to increase the effective life of gas turbine engine blades.

Bayesian optimization with active learning of design constraints using an entropy-based approach

The design of alloys for use in gas turbine engine blades is a complex task that involves balancing multiple objectives and constraints. Candidate alloys must be ductile at room temperature and retain their yield strength at high temperatures, as well as possess low density, high thermal conductivity, narrow solidification range, high solidus temperature, and a small linear thermal expansion coefficient. Traditional Integrated Computational Materials Engineering (ICME) methods are not sufficient for exploring combinatorially-vast alloy design spaces, optimizing for multiple objectives, nor ensuring that multiple constraints are met. In this work, we propose an approach for solving a constrained multi-objective materials design problem over a large composition space, specifically focusing on the Mo-Nb-Ti-V-W system as a representative Multi-Principal Element Alloy (MPEA) for potential use in next-generation gas turbine blades. Our approach is able to learn and adapt to unknown constraints in the design space, making decisions about the best course of action at each stage of the process. As a result, we identify 21 Pareto-optimal alloys that satisfy all constraints. Our proposed framework is significantly more efficient and faster than a brute force approach.

Optimization Model of the Shell Capsules Geometry for a System for Diagnosing Damage to Gas Turbine Blades in Non-stationary

Scientific research is devoted to the problem of diagnosing damage in the blades of gas turbine engines in non-stationary conditions. The paper proposes a model for a more accurate calculation of the parameters of the crack detection system using a system of capsules, inside of which, under the influence of pressure, there is a substance exhibiting ionizing properties. In the study, the relations for determining the uneven pressure due to the action of centrifugal tensile forces during the rotation of the turbine blade are obtained. The relations for calculating the minimum required diameter of the capsule to ensure the rupture of the capsule when cracks are opened for the effective operation of the crack detection system are obtained. Calculations of the pressure inside the capsule and the geometry of the capsule at different speeds of rotation of the turbine blade are carried out. An estimate of the error in calculating the pressure inside the capsule is given in the case of not taking into account the action of centrifugal forces. The obtained dependences will significantly optimize the system for detecting damage to turbine blades, and increase the efficiency and safety of the operation of gas turbine engines.

Deformation mechanisms of low cycle fatigue of a fourth generation Ni-based single crystal superalloy

Ni-based single-crystal superalloys are extensively employed in turbine blades for aircraft and industrial gas engines. The blades are subjected to complex thermal and stress impacts during service, which may cause sudden low-cycle fatigue damage and subsequent flight accidents. To investigate the relationship between the microstructure and mechanical properties, fatigue-damaged microstructures are compared under cyclic deformation at 800 and 900 °C using combined electron microscope characterizations. With an increase in temperature, the deformation is more concentrated in the γ matrix channels and the cyclic deformation behaviors stabilizes, whereas cutting the γ′ phase becomes difficult with decreasing slip bands. In addition, the significance of interfacial dislocation networks in enhancing cyclic stability and hindering cyclic tension–compression asymmetry is discussed.

The method of calculating the minimum creep rate of turbine blades of gas turbine engines based on the degradation of the alloy microstructure

In the current global economic conditions, airlines need to curtail financial expenses. It is known that the share of airline costs for maintenance and repair (MR) in the total cost structure amounts to at least 20%, of which more than 40% is for the repair and maintenance of aircraft engines (AE). According to the actual expertise, this item of expenditure will continue to grow due to the inevitable sophistication of AE structures, which is specified by the need to increase the efficiency and ecological compatibility. One of the possible ways of curbing maintenance and repair expenses is to transit for the operation of on-condition components which are currently in operation until the overhaul life is exhausted. For example, turbine blades of gas turbine engines (GTE) can be pertinent to such elements. It is a common fact that turbine blades operate in challenging environment: they are affected by excessive temperatures, severe centrifugal loads, aggressive gas media, and their destruction generally occurs because of the accumulation of fatigue damage and creep. The alloy microstructure significantly degrades and deforms before macroscopic damage develops. The early detection of microscopic damage in the alloy is the tool which allows for the transition to GTE oncondition turbine blades operation. The article presents the method for calculating the minimum creep rate of the Inconel 738LC alloy based on microstructural changes under operating conditions. The obtained results are proposed to be used for calculating the residual life of turbine blades by the creep parameter.

Effects of Part-to-Part Flow Variations on Overall Effectiveness and Life of Rotating Turbine Blades

Abstract As firing temperatures in gas turbine engines continue to increase to achieve high efficiencies, components in the main gas path must be protected with cooling flows to ensure lifing targets are met. Manufacturing variations, however, influence the performance and life characteristics of components with the same nominal design. This study presents blade flow and overall cooling effectiveness measurements for nine true-scale, aero engine turbine blades with realistic manufacturing variations. Flow measurements were made through each blade at a fixed pressure ratio to determine flow variability between holes and between blades. Infrared thermography was used to capture spatially-resolved temperature measurements reported as overall effectiveness on the same nine blades under high-speed rotating conditions at the Steady Thermal Aero Research Turbine Laboratory. Thermal performance was correlated with blade flow performance indicating substantial blade-to-blade variations resulting from manufacturing differences. Measurements also indicated wide variations in cooling jet trajectories as well as overall cooling effectiveness. Finally, the observed blade-to-blade variations in effectiveness were scaled to engine conditions with lifing estimates showing some blades would be expected to last only half as long as others due to manufacturing variability.

Analysis of a Single Crystal Solidification Process of an Ni-based Superalloy using a CAFE Model

The efficiency of gas turbines depends on the gas turbine working temperature. Single crystal blades are being applied more often than equiaxed blades in gas turbine engines, to increase the turbine inlet temperature, resulting in enhanced turbine engine efficiency. Single crystal blades endure creep conditions at high temperature better than polycrystal blades because the single crystals do not include grain boundaries. The single crystal process is a breakthrough technology, however, production yield is relatively low compared with polycrystal, and their mechanical properties depend on the crystallographic orientation of the single crystals. In this study, a thermal simulation model, the 3D cellular automation-finite element (CA-FE), was used on the single crystal process with the Bridgman method. The simulation model was well expected, by analysis of the microstructure and EBSD, on the grain selection in the single crystal process. The evolution of single crystal grains was analyzed on process of grain selection in start block and spiral selector. Single crystal orientation was also investigated to determine the effect of nucleation density, forming in the initial stage of solidification.

Hydrogen and Corrosion Resistance of Nickel Superalloys for Gas Turbines, Engines Cooled Blades

The paper presents the results of the analysis of the resistance to hydrogen and high-temperature salt corrosion of the developed alloy of the CM88Y type for the turbine blades of gas turbine engines for marine and power purposes in comparison with the industrial heat-resistant corrosion-resistant alloy CM88Y and the alloy for the protective coating of the SDP3-A blades. SDP3-A alloy was chosen as a reference sample, which has high hydrogen and corrosion resistance. The new heat-resistant alloy additionally contains such refractory metals as rhenium and tantalum, which are added to the composition of the alloy in order to increase operational characteristics while maintaining phase-structural stability. These are properties such as long-term and fatigue strength, characteristics of plasticity and strength at room and elevated temperatures. Therefore, the purpose of these studies was to determine the resistance to high-temperature salt corrosion of the developed alloy in comparison with the industrial heat-resistant nickel alloy and to evaluate the influence of alloying, hydrogen embrittlement of CM88Y and ZhS3DK alloys with different contents of chromium, boron, zirconium, hafnium, and yttrium were compared. The corrosion resistance of the materials was evaluated after crucible tests in a salt solution at a temperature of 900 °C for 30 h, according to the standard method. The corrosion resistances of alloys were determined by the mass loss, corrosion rate, and data from metallographic studies.

РАСЧЁТНОЕ ПРОГНОЗИРОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ОСТАТОЧНЫХ ДЕФОРМАЦИЙ ПРИ ИЗГОТОВЛЕНИИ ДЕТАЛЕЙ, ПОДВЕРГАЕМЫХ УПРОЧНЕНИЮ ПОВЕРХНОСТНЫМ ПЛАСТИЧЕСКИМ ДЕФОРМИРОВАНИЕМ

Ensuring the geometric accuracy of critical parts is an actual problem for aviation industry enterprises. The blades of gas turbine engines are particularly critical and technologically complex parts. In most cases, the interlocks of the blades, as well as the blade, are subjected to surface shot peening. Residual stresses are the first cause of the appearance of technological residual deformations. It is the residual deformations caused by the action of residual stresses that in most cases are the cause of critical defects of parts. Thus, the development of scientifically based approaches to modeling residual stresses and calculating technological residual deformations is an actual task. The paper presents an approach that allows at the stage of machining to take into account the deformations that can be obtained at the final stages of manufacturing parts after shot peening strengthening. The approach is based on preliminary computational prediction of technological residual deformations from the action of residual stresses based on analytical and finite element methods. The implementation of the approach is shown on the example of a compressor blade of a gas turbine engine, subjected to hardening by shot peening over the entire surface of the part.

Overview of technical solutions for improving of magnetron sputtering devices

The paper provides a brief overview of technical solutions that allow expanding the capabilities of magnetron sputtering systems using different options for organizing an external source of charges. Among them, the following are considered in detail: electron emission in the magnetron discharge track; argon ionization in the space above the target; argon ionization in the vacuum chamber volume; the use of an uncooled "hot" target; bombardment of the target surface with a beam of argon ions. Among the solutions considered, a combination of a magnetron with an ion source or an incandescent cathode is noted, which in principle can provide equal-dimensional reactive sputtering on "long" (more than 1 m) magnetrons and flexible control of the properties of coatings intended for dimensional elements of equipment of the fuel and energy and oil and gas complexes, as well as solutions based on spraying a "hot" target, which can find industrial application for the formation of thermal barrier coatings on the blades of modern power gas turbines and aviation gas turbine engines.

Additive manufacturing of titanium alloys – Enabling re-manufacturing of aerospace and biomedical components

This paper describes the state of the art of additive manufacturing of Titanium alloys especially in the high-value-materials industries such as aerospace and biomedical. In such industries, the high value components like aerospace gas engine turbine blades or the coronary angioplasty stents in biomedical industry call especially for the re-manufacturing vision that is only recently enabled by additive manufacturing methodologies. This paper starts by describing the two most common additive manufacturing (AM) methods as characterized by their input material forms: powder and wire. Using examples, it then provides an assessment of the status of these methods as regards to their maturity as production ready processes. Following this, the principal issues that must be addressed before AM can achieve this status are outlined. Perhaps the most critical one among these is development of a rapid qualification method for AM produced components. In this regard, the current method for qualifying different classes of components is outlined. Some suggestions for reducing the time required for qualification are made. Significant benefits of AM are described including part count reduction and the use of design synthesis to achieve significant component weight reduction. Two low risk examples of this are described herein. The Direct Energy Deposition (DED) model is highlighted especially in its role to enable the Re-Manufacturing vision for high-value structural components such as in aerospace and biomedical industries. This paper concludes that there are numerous opportunities for incorporation of components made by AM once some of the issues described are effectively addressed.

Formation of lamellar microstructure in Ti-48Al-7Nb-2.5V-1Cr alloy

The reasonable design and application of phase transformation is an efficient approach to coordinate the microstructure and properties of alloys. The sequence of compositional and structural transformation determines the type and mechanism of phase transformation. Because of their low density and excellent high-temperature properties, TiAl alloys that contain fully lamellar microstructure have been applied to low-pressure turbine engine blades. However, there is no consensus on the mechanism of lamellar formation. Here, we propose a new mechanism that is dominated by spinodal decomposition, in which compositional transformation occurs prior to structural transformation during lamellar formation. Transitional lamellae with fcc-based long-period superstructures are introduced to prove the mechanism of sequentially spinodal decomposition, shear transformation, compositional modulation and ordering.

Effect of Annealing Treatment on the Recrystallization of a Single Crystal Superalloy

Recrystallization often occurs in the production of aero engine turbine blades of single crystal superalloys. It is believed that annealing treatment can reduce the recrystallization tendency, as some of the casting residual stress is released. To evaluate the annealing effect on recrystallization, tensile test is carried out in present study for as-cast specimens of a second generation single crystal superalloy to induce stress. Two different annealing treatments are applied to the prestrained specimens, followed by the solution treatment at 1300°C for 2h. In order to compare the effect of the annealing treatments, the specimens are investigated by x-ray Laue diffraction technique and metallographic observation. According to the comparison, the more effective annealing treatment is recommended.

CAMERA: A method for cost-aware, adaptive, multifidelity, efficient reliability analysis

Estimating probability of failure in aerospace systems is a critical requirement for flight certification and qualification. Failure probability estimation involves resolving tails of probability distributions, and Monte Carlo sampling methods are intractable when expensive high-fidelity simulations have to be queried. We propose a method to use models of multiple fidelities that trade accuracy for computational efficiency. Specifically, we propose the use of multifidelity Gaussian process models to efficiently fuse models at multiple fidelity, thereby offering a cheap surrogate model that emulates the original model at all fidelities. Furthermore, we propose a novel sequential acquisition function based experiment design framework that can automatically select samples from appropriate fidelity models to make predictions about quantities of interest at the highest fidelity. We use our proposed approach in an importance sampling setting and demonstrate our method on the failure level set and probability estimation on synthetic test functions and two real-world applications, namely, the reliability analysis of a gas turbine engine blade using a finite element method and a transonic aerodynamic wing test case using Reynolds-averaged Navier-Stokes equations. We show that our method predicts the failure boundary and probability more accurately and at a fraction of the computational cost compared with using just a single expensive high-fidelity model. Finally, we show that our sequential approach is guaranteed to asymptotically converge to the true failure boundary with high probability.

Thermally Grown Oxide Stress in PS-PVD and EB-PVD Thermal Barrier Coatings Observed at Various Lifetimes Via Synchrotron X-ray Diffraction

Abstract The current standard application method for thermal barrier coatings (TBCs) on turbine blades for jet engines is electron-beam physical vapor deposition (EB-PVD) due to its high strain tolerance and low thermal conductivity. An emerging deposition method, plasma-spray physical vapor deposition (PS-PVD), presents an opportunity for a tailorable microstructure, and non-line-of-sight deposition that is faster and less expensive. To compare the lifetime behavior of both PS-PVD and EB-PVD coatings, samples subjected to 300 and 600 thermal cycles were measured during a 1 h thermal cycle to determine the strains, which were converted to stress, in the thermally grown oxide (TGO) layer of the TBCs using synchrotron X-ray diffraction (XRD). Room temperature XRD measurements indicated among samples that PS-PVD coatings experienced greater variation in in-plane room temperature strain in the TGO after cycling than the EB-PVD coatings. In-situ XRD measurements indicated similar high-temperature strain and no spallation after 600 thermal cycles for both coatings. Microscopy imaging after cycling showed greater rumpling in PS-PVD coatings that led to different failure modes between the two coatings’ TGO layers. The tailorability of PS-PVD coatings allows for adjustments in the processing parameters to improve their overall performance after aging and bridge the differences between the two deposition methods.

A Review of Laser Peening Methods for Single Crystal Ni-Based Superalloys

Single crystal Ni-based superalloys are often used to create gas turbine engine blades for their high strength under intense thermo-mechanical loading. Though they are remarkably capable under these conditions, a particular class of premature failure mechanisms known as surface-initiated damage mechanisms can lead to the early fracture of an otherwise healthy blade. This review paper discusses the current progress of post-processing techniques that can greatly mitigate the potency of surface-initiated damage mechanisms. In particular, laser peening (LP) is of significant interest due to the relatively low amount of cold work it induces, greater depth of compressive residual stresses than other cold working methods, ability to accommodate complex part geometries, and the minuscule effect it has on surface roughness. The residual stresses imparted by LP can greatly hinder crack growth and consequently allow for enhanced fatigue life. Given that turbine blades (constructed with single crystal Ni-based superalloys) are prone to fail by these mechanisms, LP could be a worthy choice for increasing their service lives. For this reason, initiative has been taken to better understand the mechanical and microstructural modifications imparted by LP on single crystal Ni-based superalloys and a summary of these investigations are presented in this review. Results from several works show that this class of alloy responds well to LP treatment with improvements such as ~30–50% increase in microhardness, 72% increase in low cycle fatigue life, and elevated resistance to hot corrosion. The primary objective of this review is to provide insight into current state-of-the-art LP techniques and summarize the findings of numerous works which have utilized LP for increasing the service lives of single crystal Ni-based superalloy components.

Experimental and Computational Study of Mechanical and Thermal Characteristics of h-BN and GNP Infused Polymer Composites for Elevated Temperature Applications

Polymer-based nanocomposites are being considered as replacements for conventional materials in medium to high-temperature applications. This article aims to discover the synergistic effects of reinforcements on the developed polymer-based nanocomposite. An epoxy-based polymer composite was manufactured by reinforcing graphene nanoplatelets (GNP) and h-boron nitride (h-BN) nanofillers. The composites were prepared by varying the reinforcements with the step of 0.1 from 0.1 to 0.6%. Ultrasonication was carried out to ensure the homogenous dispersion of reinforcements. Mechanical, thermal, functional, and scanning electron microscopy (SEM) analysis was carried out on the novel manufactured composites. The evaluation revealed that the polymer composite with GNP 0.2 by wt % has shown an increase in load-bearing capacity by 265% and flexural strength by 165% compared with the pristine form, and the polymer composite with GNP and h-BN 0.6 by wt % showed an increase in load-bearing capacity by 219% and flexural strength by 114% when compared with the pristine form. Furthermore, the evaluation showed that the novel prepared nanocomposite reinforced with GNP and h-BN withstands a higher temperature, around 340 °C, which is validated by thermogravimetric analysis (TGA) trials. The numerical simulation model is implemented to gather the synthesised nanocomposite’s best composition and mechanical properties. The minor error between the simulation and experimental data endorses the model’s validity. To demonstrate the industrial applicability of the presented material, a case study is proposed to predict the temperature range for compressor blades of gas turbine engines containing nanocomposite material as the substrate and graphene/h-BN as reinforcement particles.

Theoretical and experimental evaluations of pre-swirl rotor-stator system with inner seal bypass configuration for turbine performance improvement

Pre-swirl system has strong potential to improve the cooling performance and service life of high-pressure turbine rotor blades in gas turbine engines. This study is to evaluate and improve the temperature drop and power consumption characteristics of the pre-swirl system with multi-in and multi-out seal flow by theoretical and experimental analysis. Then, a high-speed rotating test rig of the pre-swirl rotor-stator system is established, considering the inner seal by-pass configuration to prevent the flow of hot gas into the pre-swirl cavity. In addition, the rotor-stator domain parameters in the pre-swirl system test rig are accurately measured at high-speed operating conditions. Three experimental schemes of pre-swirl systems are proposed for comparison under different operating conditions. The experimental results show that the temperature drop of the prototype pre-swirl system is in the range of 9.28–20.78 K, with the power consumption of the system ranging between −0.23 and −6.67 kW and the system pressure ratios being around 1.3–1.9. Because of the inner seal inflow ratio ranging within 0–15%, the system temperature drops for the improved pre-swirl system built-in inner seal by-pass passages notably reach a value between 12.12 K and 25.54 K with an average system power consumption within −0.41 to −8.21 kW. Thus, the improved pre-swirl system arrangement has dual advantages of a higher cooling effect and lower power consumption.