Blade Material Research Articles

Microstructure degradation of service-exposed turbine blades made of directionally solidified DZ125 superalloy

The investigation about the degradation behavior of turbine blades exposed to complex and extreme environments for long-term service is of great importance to assess the remaining life of the blades. In our work, the microstructure at different positions of the service-exposed turbine blade was characterized from the micron scale to the nanoscale. The results showed that there are noticeable differences in the microstructure at different positions of the blade and the blade has a complex service history. These conclusions suggest that the most severely damaged part of the blade should be responsible for assessing the remaining life of the blade, moreover, the mechanical properties of materials should not be limited to life at constant temperature and stress, rather non-isothermal and variable stress tests are more instructive in assessing the performance or life of aircraft engine blade materials.

Surface integrity and fatigue performance of GH4169 superalloy using abrasive belt grinding

GH4169 superalloy is the key material for advanced aero-engine high-temperature blades. Improving the surface integrity of the GH4169 superalloy after machining is conducive to improving fatigue performance, which is of great significance for the long-term stable service of the aero-engine. Abrasive belt grinding can effectively improve the surface integrity of GH4169, but the influence of surface integrity on fatigue performance after belt grinding with different process parameters has not been fully revealed. The grinding experiments on the influence of different process parameters on GH4169 surface integrity were carried out, and the influence of process parameters on surface morphology, roughness, and residual stress was explored. On this basis, fatigue experiments were carried out on the samples processed with typical process parameters at 80 % yield strength. The influence of process parameters on fatigue performance was discussed in combination with the surface integrity and cross-section of four groups of samples. The results show that different abrasive belt grinding process parameters can significantly change the surface morphology, roughness, residual stress, and other surface integrity indexes. Roughness mainly affects stress concentration. Macroscopically, the greater the roughness is, the easier crack initiation is. Sample 3 with the smallest roughness is 111.04 % higher than Sample 1. The residual stress can inhibit crack initiation and slow crack propagation. Even under large roughness, the fatigue life of Sample 4 is still better than that of Sample 1, and the stable propagation rate of Sample 4 is 32.4 % slower than that of Sample 3. Considering the anti-fatigue performance and processing efficiency, the linear speed range is 11 to 15 m/s, the feed speed range is 5 to 9 mm/s, and the grinding depth is 0.1 to 0.25 mm.

Investigating the effect of powder recoater blade material on the mechanical properties of parts manufactured using a powder-bed fusion process

As additive manufacturing (AM) technology grows, more industries are learning how to utilize it for their specific applications. Powder bed fusion-based AM processes such as Direct metal laser solidification (DMLS) allow manufacturers to design more intricate or lightweight parts that could not be made with traditional tools. DMLS expands the capabilities of manufacturing, but the recoater blade that spreads powder presents challenges in printing delicate details such as lattice structures and high aspect ratio features. Hard steel or ceramic blades are often used to compact powder to create smooth, even layers that result in higher strength values of parts. However, small structures can be damaged by these blade types. Alternatively, a softer rubber or carbon fiber brush can be used to make the printing process easier by not breaking the small, printed features. On the other hand, parts made with softer blades are expected to have less strength and more defects. To compare the mechanical properties of finished parts due to blade type, 3 blade materials, high-speed steel (HSS), silicone rubber, and carbon fiber brush, were compared in this study. Tensile bars, cubes, and Voronoi lattice structure pucks were printed and analyzed for tensile properties, optical density analysis, as well as compression strength or toughness. These tests are often completed by original equipment manufacturers (OEM’s) in the AM industry to qualify the machine’s process. There were no significant tensile strength differences noticed of parts based on blade type and the values were all within the tolerance of OEM specifications. Optical density analysis indicated that the rubber blade builds have a higher number of large defects, greater than 75 μ m, and the brush blade has a higher number of small defects, less than 75 μ m in size. The HSS blade has zero defects greater than 90 μ m. There was no significant difference in maximum compression strength for the three blades, but the HSS blade produces parts with a standard deviation of toughness that is half of the other two blades. Inconsistencies shown in the soft blade builds may be due to the nature of the soft blades wearing faster over time during each build, however, the soft recoater blades can be a useful option if the application allows for occasional inconsistency.

Coupled heat transfer analysis of internal and film cooling of turbine blade under medium temperature conditions

• The coupled heat transfer of the internal cooling and film cooling are studied. • The effect of the heat conduction of solid regions on the heat transfer is checked. • The film hole enhances the flow and heat transfer of the internal channel. • The ribs increase the overall cooling effectiveness near the downstream of film hole. • The coupled heat transfer analysis contributed to find the fine design of blade. Increasing turbine inlet gas temperature is a main approach to meet the demands for high efficiency and thrust of advanced gas turbine engines. Both of internal and film cooling are often used at the same time for the turbine blade’s cooling to enhance the overall cooling performance and ensure the blade temperature below to the heat resistance temperature of blade material. Most of open studies focused on the individual cooling effect of either internal cooling or film cooling under normal temperature conditions. However, the actual working conditions of blade cooling is that internal cooling and film cooling affect each other because of the coolant flow through film hole and the heat conduction inside the blade solid regions (including the internal disturbing elements). In addition, the temperature difference between turbine inlet gas and coolant is much high. It is found that there are few studies on the coupled heat transfer characteristics of turbine blade cooling. To establish a numerical method for coupled heat transfer analysis of the turbine blade cooling, the coupled heat transfer in two perpendicular channels which are connected by a dividing wall and a film hole through the dividing wall is numerically investigated by simultaneously solving the air flow and convective heat transfer equations in the two passages. The heat conduction through the dividing wall (including the ribs equipped in the internal channel) and the flow through the film hole are also taken into consideration. The interaction between internal and film cooling can thus be explored. The mainstream inlet temperature is set to be 709 K to consider a medium temperature condition of turbine blade, and Reynolds number is 1.08 × 10 5 . The large-eddy simulation (LES) and SST κ-ω are employed to verify the applicability of turbulence models for the simultaneous simulation of internal and film cooling by comparing the numerical consequence with experiment from the published literature. It is indicated that LES can capture the fine structure of the flow field and has high accuracy in predicting the cooling effect. It is discovered that the heat conduction through the dividing wall of the two channels increases both of the internal convective cooling and the film cooling of the mainstream channel in comparison to the adiabatic cooling effect without considering the heat conduction inside the solid regions. In addition, the outflow through the film hole improves Nusselt number of internal channel, and the ribs bring about a slight increase of overall cooling effectiveness near the behind zone of the film hole, but decrease in the downstream a little far from the film hole. Besides, adjusting the blowing ratio could achieve higher blade cooling performance. It is suggested that we should not stay in the stage of studying internal or film cooling separately, but carry out more coupled heat transfer analysis of turbine blade cooling to find the appropriate geometric parameter/configuration of internal and film cooling for the fine design of gas turbine blade cooling, especially today when large-scale numerical calculation has become a reality.

ANALISIS TEGANGAN PISAU PENCACAH LIMBAH KAKAO DENGAN METODE BEDA HINGGA

One of the vital components of a crushing machine is a crushing blade. Where the crusher blade works and is in direct contact with the cocoa waste to be crushed. Many crushing blades wear out quickly after being used for a short time because the blade material has low strength.The aim of this study was to analyze the blade in the crusher machine used by farmers to handling cocoa waste. The blade usings material of steel by utilizing waste car spring sheets with ASTM A29 steel type which is formed into a crusher blade because the price is cheap and easy to obtain. 3-D finite element design and analysis were carried out using Solidwork software. The blade is given a load variation from 100N - 1000N to determine the value of stress, deformation, and safety factor. The results of the simulation and analysis on the crusher blade show a downward trend starting at a load of 400 N, where the stress is 444,738 N/mm2, the maximum shape change is 3.48066 mm, and the safety factor seems to be low in the red distribution with FOS below 1, which is 0.989347.

Multi-objective optimization and modeling of a natural fiber hybrid reinforced composite (PxGyEz) for wind turbine blade development using grey relational analysis and regression analysis

Due to the increasing demand for clean and sustainable energy, wind turbine technology has also witnessed significant developments in terms of its output capacity which is proportional to its size (length of wind turbine blades). The only limitation to this scaling is the availability of applicable materials with expected strength and low weight which can support a longer span wind turbine blade. Although studies have been carried out on alternate materials for the development of wind turbine blades, the use of Grey Relational Analysis for the optimization of natural fiber-reinforced composites for this application is rare. Also, pineapple leaf fiber, having considerable mechanical properties and low density has not been optimally considered as reinforcement in this regard. This is a robust study concerned with developing more eco-friendly materials for application in the manufacture of wind turbine blades. In this study, a material PxGyEz, a natural fiber/synthetic fiber polymer composite was developed and optimized based on the major criteria for selecting materials for wind turbine blades which are high tensile strength, high flexural strength, and low density. Grey relational analysis coupled with the Taguchi robust optimization technique was used for the optimization process and statistical analysis was employed to know the percentage contribution of each of the variable parameters (PALF volume percentage, glass fiber volume percentage, and fiber length) to the grey relational grades. The material P10G20E15 was the optimum having a grey relational grade of 0.7977 at experimentation and tensile strength of 95.3144 MPa, a flexural strength of 92.818 MPa, and a density of 1.3274 g/cm3. SEM analysis showed microstructural formations that explained the mechanical and physical behavior of the optimized hybrid composite. Simulation of an NREL 5 MW wind turbine blade developed with the optimized material P10G20E15 proved reliable for service with a 64% reduction in weight.

Estimation of dynamic characteristics of a wind turbine blade

Wind energy is considered a clean source of energy that can be used efficiently to produce electricity without any harmful emissions. A wind turbine is an electro-mechanical system that converts the wind's kinetic energy into electricity. A typical wind turbine consists of three components, viz. the rotor (which includes the turbine blades), generator and the supporting structure. The turbine blades are a critical component of any wind turbine. They comprise of numerous airfoil sections with varying chord lengths and twist angles, that are combined together to form a three-dimensional blade surface. When generating electrical power through rotating motion, they are subjected to different loads, such as wind, gravitational, and centrifugal loads. The sheer size of the turbine blade necessitates the use of light and strong materials, and composites are well suited for this. The selection and manufacturing of suitable composite material is critical to blade design as it directly affects the efficiency and power of wind power plants. With blades that are continuously exposed to large wind loads, it is essential to determine the natural frequencies of vibrations at which they occur and understand the consequences. Large amplitude vibrations can induce dynamic stresses and accelerate the fatigue of the blade material leading to blade breakage. Thus, it is of significant importance to analyse the dynamic behaviour of these structures. This study aims to investigate the effect of varying fiber orientation and volume fraction on natural frequencies and vibration modes of the turbine blade.

Residual Stress Enhancement by Laser Shock Treatment in Chromium-Alloyed Steam Turbine Blades.

In-service turbine blade failures remain a source of concern and research interest for engineers and industry professionals with attendant safety and economic implications. Very high-pressure shock impacts from laser shots represent an evolving technique currently gaining traction for surface improvement and failure mitigation in engineering components. However, the physical characteristics and effects of parameter variations on a wide range of materials are still not fully understood and adequately researched, especially from a computational point of view. Using the commercial finite element code ABAQUS©, this paper explores the application of laser shock peening (LSP) in the enhancement of residual stresses in Chromium-based steel alloyed turbine blade material. Results of the numerically developed and experimentally validated LSP model show that peak compressive residual stresses (CRS) of up to 700 MPa can be induced on the surface and sub-surface layers, while the informed varying of input parameters can be used to achieve an increase in the magnitude of CRS imparted in the peened material. Analysis of the hierarchy of influence of the five input parameters under investigation on residual stress enhancement reveals the laser shock intensity as the most influential, followed in descending order of influence by the exposure time, shot size, degree of overlaps, and the angle of shot impact.

Elevated temperature erosion of abradable seal coating

Abradable coatings are essentially sealing materials and are deposited by thermal spray techniques. The main function of these coatings is to control the clearance of the gas path of the gas turbine engines. The abradable coating prevents turbine blade damage by abrading itself when there is an offset or vibration during turbine operation. Since the coating is meant to abrade, the preferred coating material is relatively softer than the turbine blade material. As these coatings are prone to solid particle erosion at high temperatures, the erosion response of these coatings at elevated temperatures needs to be investigated. In order to achieve this objective, MCrAlY boron nitride polymer coating was deposited employing an air plasma spraying technique on a Ni-base alloy substrate. The important features of the microstructure and mechanical properties of the coating were examined, and the coating was subjected to erosion at various temperatures under different erosion conditions. The results indicate a ductile erosion behaviour for an abradable top coat. The erosion rate increases with the temperature of the coating. The detailed results of the investigation are presented, and the erosion mechanisms are studied.

Recycling wind turbine blades

Wind turbines generated roughly 6% of the world’s electricity in 2020. Industry analysts predict that number will grow by more than 6% annually this decade. As the wind industry grows, so does the number of aging and damaged turbine blades that are being decommissioned and replaced with larger, more efficient ones. In the US alone, some 8,000 blades were pulled down in 2021. Most blades were landfilled because there wasn’t much else that could be done with them. But several companies are working on ways to recycle the enormous blades by shredding them and reusing the fiberglass and plastic resin to make cement, tough industrial plastics, and other products. Further advances in recycling technology along with changes in blade materials and recycling economics may be needed to deal with used blades on a global scale sustainably. Bob Cappadona laughs as he recalls an inquiry in 2020 from General Electric about

Research on the feasibility of polyethylene terephthalate foam used in wind turbine blades

AbstractThe sandwich foam materials of wind turbine blades are mainly polyvinyl chloride (PVC) and styrene–acrylonitrile (SAN) foams due to their good mechanical properties. However, PVC foam is unrecyclable and not resistant to high‐temperature conditions, while SAN foam is more expensive than PVC foam. Polyethylene terephthalate (PET) has irreplaceable advantages than both PVC and SAN foams because of its better mechanical performance, fantastic heat‐resistant, low cost, and environmental friendliness (100% recyclability). In this article, the mechanical properties, thermal stability, resin uptake, and cellular morphology of PET T92, PVC H60, and SAN T400 foams were discussed. The results showed that the mechanical properties of T92 were equivalent to the existing H60 and T400, and even exceed their properties. It was found that the thermal stability of T92 was better than H60 and T400 under the same high temperature. Moreover, the pore of T92 was more uniform and regular than H60 and T400. Furthermore, the overall cost of T92 was lower than H60 and T400. The findings suggest that PET foam with a density of 100 kg/m3 can completely replace PVC 60 kg/m3 and SAN 71 kg/m3 foams from the perspective of mechanical performance, cost, thermal stability, and environmental protection.

Study on subsurface damage and recrystallization of single crystal superalloy in scratching with single diamond grain

Single crystal superalloy has gradually become the primary manufacturing material of advanced aero-engine turbine blades. However, it is easy to introduce subsurface damage and recrystallization in the precision machining process of this kind of material, and hence to worsen the high-temperature service performance of the parts. To explore its damage mechanism and influencing factors, a series of scratching experiments of single crystal superalloy with single diamond grain were conducted in this work. The examined results of the machined sample section by using a scanning electron microscope indicated that the subsurface damages include metallographic plastic deformation, slip band and transverse crack before heat treatment. Furthermore, cellular recrystallization observed in the surface layer mainly occurred in the metallographic plastic deformation zone after heat treatment. The experimental results revealed that the recrystallization depth increased with a rise in tool dimension and normal components of the scratching force. When the normal force is less than 20 N, the recrystallization depth scratched by the 80° tool is less than the critical safety value of 15 μm. Further analytical results indicated that improving the tool cutting performance and reducing the cutting force are beneficial to reduce the degree of recrystallization and subsurface damages. The research finding of this work is expected to provide a theoretical basis for the high efficiency and low damage machining of single crystal superalloy.

Effect of γ' particles morphology on dynamic strain aging behavior of Udimet 500 superalloy

The Udimet 500 superalloy is a promising candidate material for power plant gas turbine blades due to its excellent mechanical properties at high temperatures. However, dynamic strain aging (DSA) behavior of the Udimet 500 superalloy during high-temperature tensile test has not been investigated so far. In the present study, the effect of γ' particles size and volume fraction on dynamic strain aging behavior of the Udimet 500 superalloy were investigated in the terms of serration frequency and magnitude. The serrated flow was observed in the stress-strain curves during plastic straining at 800 °C. The results illustrated that the γ' particles morphology has significant effect on serration frequency, serration magnitude, and fracture mechanism of the Udimet 500 superalloy. Although, the serration frequency decreased with reducing γ' particles size and increasing γ' particles volume fraction, the serration magnitude increased. The governing mechanism for dynamic strain aging of the Udimet 500 superalloy have been proposed by dislocation interactions with solute atoms and γ' particles. Furthermore, a non-zero work hardening rate is observed during Lüders elongation which was attributed to high volume fraction of γ' particles in precipitation strengthened superalloys. The effect of dynamic strain aging on fracture mechanism was also investigated. When dynamic strain aging was absent, the dimples initiated at the γ/γ' interfaces during room temperature tensile test. Dynamic strain aging inhibits dimples formation at the γ/γ' interfaces.

Numerical Analysis of Conjugated Heat Transfer and Thermal Stress Distributions in a High-Temperature Ni-Based Superalloy Turbine Rotor Blade

This paper establishes a multidisciplinary method combining conjugate heat transfer (CHT) and thermal stress for a high-temperature Ni-based superalloy turbine rotor blade with integrated cooling structures. A conjugate calculation is performed to investigate the coolant flow characteristics, heat transfer, and thermal stress of the rotor blade under rotating and stationary conditions to understand the effects of rotation on the multidisciplinary design of the blade. Furthermore, the maximum resolved shear stress among the 30-slip systems and the corresponding dominant slip system are obtained to predict the deformation tendency of the blade by employing the crystal plasticity finite element method (CPFEM) and considering the specified anisotropic blade material (GTD-111). The results show that the forces of rotation, including centrifugal and Coriolis forces, and their induced buoyancy force, alter the coolant flow field and thus affect the rotor blade’s heat transfer distribution compared with the stationary condition. The maximum temperature and thermal stress of the rotor blade under rotating conditions are reduced by 5% and 21% compared with that under the stationary condition, respectively. Compared with the stationary condition, the temperature and thermal stress distribution on the blade under the rotating condition are more uniform, especially on the suction side. In addition, the blade root connecting with the hub, the film holes near the leading-edge region at the blade root, the mid-chord of the suction surface, and the grooved blade tip are easily damaged by the enormous resolved shear stress and the interface effect of different types of dominant slip system under the two conditions. In this work, it was feasible to use the cascade cooling effect test to analyze the dynamic test results for the rotor blade. Furthermore, the thermal stress analysis based on the CPFEM can provide a superior level of blade cooling design than CHT by considering the anisotropic material characteristics of a turbine blade.

Multiobjective Optimization of Composite Wind Turbine Blade.

When designing a wind turbine, the main objective is to generate maximum effective power with the lowest possible production costs. The power of a wind turbine depends primarily on the aerodynamic properties of its blades. Moreover, the cost of making a blade for a wind turbine, and therefore also for the entire wind turbine, depends on the materials used for its production. Therefore, wind turbine blades are the most studied element of a wind turbine. By selecting the optimal material and geometric properties of the wind turbine blade, it is possible to reduce the costs of making the entire wind turbine. These rationales led the authors to investigate composite wind turbine blades. A two-criteria optimization task was formulated, which allowed for the simultaneous consideration of two criteria: minimizing the mass and minimizing the vertical deflection of the wind turbine blade. Geometric properties of the blade, influencing the considered criteria, were assumed as decision variables. The weighted sum method was used. The results obtained allowed us to determine the optimal geometric and material properties of a wind turbine blade.

Effect of Formic Acid on Pitting Corrosion of Steam Turbine Blade Material 13Cr Steel in Simulated Boiler Water Containing Chloride Ions

Effect of Formic Acid on Pitting Corrosion of Steam Turbine Blade Material 13Cr Steel in Simulated Boiler Water Containing Chloride Ions

Simulation studies on the comparison of different superalloys used in gas turbine blades

Impingement of gases at high temperature and pressure leads to the development of stresses and deformation in gas turbine blades. Other important characteristics are also getting changed, prompting more problems in gas turbine engines, as they are used in both power generation and transportation. In this work, failure aspects in blades is studied by performing structural analysis, considering superalloys that are used in the industry. Software packages like Solidworks and Ansys are used for modelling, meshing and solving, in order to identify the target variables like total deformation, von Mises stress, strain energy and fatigue. Geomtery of the turbine blade is modelled and after meshing, boundary conditions like pressure, force and rotational speed are enforced. Results are analysed after carrying out the static structural analysis in Ansys work bench. For the superalloy materials chosen, contours and plots are made for all the configurations. Validation of deformation from the present work is done with experiments done earlier, which is in good agreement. Total deformation is more at the tip of the blade. At the root of the blade, the stresses are found to be more. Presence of strain energy is more near the root. Fatigue life contours showed similarity in all the cases. The blade failure region is identified for all the materials under consideration and the trends are compared for different input temperatures. Thus the current work is helpful in recognizing appropriate superalloy to be used in the present day gas turbines and supports the use of GTD 111 as gas turbine blade material.

Synthesis of a novel MoSS+Mo5SiB2+Mo5Si3 based Mo–Si–B alloy and its enhanced fracture toughness

Mo–Si–B based alloys are promising ultrahigh-temperature structural materials for turbine blades. Different from traditional MoSS (Mo solid solution)+Mo5SiB2+Mo3Si based alloy, present paper focuses on a novel non-equilibrium MoSS + Mo5SiB2+Mo5Si3 based alloy, which shows more potential for excellent comprehensive performance. This alloy was synthesized by SPS (spark plasma sintering) technique using pure Mo and Mo5SiB2+Mo5Si3 powders as raw materials. SEM, EDS, XRD, EPMA, single-edge notched bending and nano-identation tests were used to reveal the formation mechanism of this alloy and evaluate its fracture toughness. The results showed that this MoSS + Mo5SiB2+Mo5Si3 based alloy was composed of MoSS, Mo5SiB2, Mo5Si3 and a little Mo3Si. Mo5SiB2+Mo3Si halos were found around the original Mo5SiB2+Mo5Si3 particles as a result of inter-diffusion between Mo and Mo5SiB2+Mo5Si3 during sintering processes. Compared with traditional cast or reaction sintered MoSS + Mo5SiB2+Mo3Si based alloy with the same composition, this MoSS + Mo5SiB2+Mo5Si3 based alloy showed superior fracture toughness benefiting from its higher MoSS content, larger coarseness of MoSS and lower Si concentration in MoSS.

Computational investigation into the effect of material properties on aeroacoustics based damage detection from wind turbine blades

A wind turbine blade monitoring system would provide significant benefit to wind farm owners and operators by reducing operation and maintenance costs and increasing energy production by limiting turbine downtime. Previous work has demonstrated potential success of a system based on monitoring the flow-generated sound with blade internal cavity microphones. In this study, the effect of blade material acoustic properties is investigated to provide recommendations on the potential application of this approach. A reduced-order model is used to identify the flow-generated lumped-parameter acoustic sources outside the blade at a frequency of 10 kHz. A feasible range of acoustic properties is used for the blade and shear web acoustic transmission coefficient and acoustic reflection coefficient. Damage detection success improved as reflection increased, as more sound propagated toward to the root of the blade. However, the damage detection success rate did not consistently increase with an increase or decrease in the transmission coefficient and balance must be achieved depending on the specific blade and the expected flow-generated sound. These results demonstrate the usefulness of quantifying the blade material acoustic properties and will be used to strategically design a blade monitoring system.

Sensitivity of transpiration cooled gas turbine cycle efficiency and coolant requirement to changes in cooling parameters

The maximum temperature at the gas turbine inlet gets restricted due to metallurgical constraints, which can be increased using blade cooling. Among different techniques for cooling blades in the gas turbine, the transpiration cooling of blades permits quite a high temperature at the turbine inlet. The objective of this study is to analyse the sensitivity of transpiration cooled gas turbine cycle performance for cooling parameterssuch as allowable blade material temperature, film cooling effectiveness, and internal cooling efficiency, so that the most important cooling parameters may be focused upon for the improvement of gas turbine cycle performance. In this study, it is found that the cycle efficiency is more sensitive to allowable blade material temperature followed by film cooling effectiveness and to internal cooling efficiency only a little bit. This study shows that with the use of cooling, for an increase in allowable blade temperature by 50 K, the gas turbine cycle efficiency increases by 0.15% . Also, the increase in film cooling effectiveness from 0.4 to 0.5 increases the cycle efficiency by 0.13% . Furthermore, with an increase in cooling efficiency from 0.7 to –0.8 the cycle efficiency increases by 0.03% only.