The Influence of Crystal Orientation on the Elastic Stresses of a Single Crystal Nickel-Based Turbine Blade

2011 ◽  
Author(s):  
Michael W. R. Savage
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Fatigue Resistance ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Casting Process ◽  
Directionally Solidified ◽  
Element Analysis ◽  
Angle Variation ◽  
Elastic Stresses

Single crystal nickel-based turbine blades are directionally solidified during the casting process with the crystallographic direction [001] aligned with the blade stacking axis. This alignment is usually controlled within 10°, known as the Primary angle. The rotation of the single crystal about the [001] axis is generally not controlled and this is known as the Secondary angle. The variation in Primary and Secondary angles relative to the blade geometry means that the stress response from blade to blade will be different, even for the same loading conditions. This paper investigates the influence of single crystal orientation on the elastic stresses of a CMSX-4 turbine blade root attachment using finite element analysis. The results demonstrate an appreciable variation in elastic stress when analysed over the controlled Primary angle, and are further compounded by the uncontrolled Secondary angle. The maximum stress range will have a direct impact on the fatigue resistance of the turbine blade. By optimizing the Secondary angle variation the elastic stresses can be reduced, giving the potential to enhance the fatigue resistance of the turbine blade.

The Influence of Crystal Orientation on the Elastic Stresses of a Single Crystal Nickel-Based Turbine Blade

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Michael W. R. Savage
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Fatigue Resistance ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Casting Process ◽  
Directionally Solidified ◽  
Element Analysis ◽  
Angle Variation ◽  
Elastic Stresses

Single crystal nickel-based turbine blades are directionally solidified during the casting process with the crystallographic direction [001] aligned with the blade stacking axis. This alignment is usually controlled within 10 deg, known as the Primary angle. The rotation of the single crystal about the [001] axis is generally not controlled and this is known as the Secondary angle. The variation in Primary and Secondary angles relative to the blade geometry means that the stress response from blade to blade will be different, even for the same loading conditions. This paper investigates the influence of single crystal orientation on the elastic stresses of a CMSX-4 turbine blade root attachment using finite element analysis. The results demonstrate an appreciable variation in elastic stress when analyzed over the controlled Primary angle, and are further compounded by the uncontrolled Secondary angle. The maximum stress range will have a direct impact on the fatigue resistance of the turbine blade. By optimizing the Secondary angle variation the elastic stresses can be reduced, giving the potential to enhance the fatigue resistance of the turbine blade.

Aero Engine Test Experience With CMSX-4® Alloy Single-Crystal Turbine Blades

1996 ◽  
Vol 118 (2) ◽  
pp. 380-388 ◽  
Author(s):  
K. P. L. Fullagar ◽  
R. W. Broomfield ◽  
M. Hulands ◽  
K. Harris ◽  
G. L. Erickson ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Single Crystal ◽  
Turbine Blade ◽  
Hot Corrosion ◽  
Turbine Blades ◽  
Casting Process ◽  
Creep Rupture ◽  
Coating Performance ◽  
Turbine Engine ◽  
Mechanical Fatigue

A team approach involving a turbine engine company (Rolls-Royce), its single-crystal casting facilities, and a superalloy developer and ingot manufacturer (Cannon-Muskegon), utilizing the concepts of simultaneous engineering, has been used to develop CMSX-4 alloy successfully for turbine blade applications. CMSX-4 alloy is a second-generation nickel-base single-crystal superalloy containing 3 percent (wt) rhenium (Re) and 70 percent volume fraction of the coherent γ′ precipitate strengthening phase. Its finely balanced composition offers an attractive range of properties for turbine airfoil applications. In particular the alloy’s combination of high strength in relation to creep-rupture, mechanical and thermal fatigue, good phase stability following extensive high temperature, stressed exposure and oxidation, hot corrosion and coating performance, are attractive for turbine engine applications where engine performance and turbine airfoil durability are of prime importance. The paper details the single-crystal casting process and heat treatment manufacturing development for turbine blades in CMSX-4 alloy. Competitive single-crystal casting yields are being achieved in production and extensive vacuum heat treatment experience confirms CMSX-4 alloy to have a practical production solution heat treat/homogenization “window.” The creep-rupture data-base on CMSX-4 alloy now includes 325 data points from 17 heats including 3630 kg (8000 lb) production size heats. An appreciable portion of this data was machined-from-blade (MFB) properties, which indicate turbine blade component capabilities based on single-crystal casting process, component configuration, and heat treatment. The use of hot isostatic pressing (HIP) has been shown to eliminate single-crystal casting micropores, which along with the essential absence of γ/γ′ eutectic phase, carbides, stable oxide, nitride and sulfide inclusions, results in remarkably high mechanical fatigue properties, with smooth and particularly notched specimens. The Re addition has been shown not only to benefit creep and mechanical fatigue strength (with and without HIP), but also bare oxidation, hot corrosion (sulfidation), and coating performance. The high level of balanced properties determined by extensive laboratory evaluation has been confirmed during engine testing of the Rolls-Royce Pegasus turbofan.

Development of Life Prediction Method of Turbine Blade Using the Theory of Critical Distance

2012 ◽  
Author(s):  
Tetsuya Nakahara ◽  
Yusuke Ueda ◽  
Hiroshi Nakamura
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Contact Surface ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Prediction Method ◽  
Critical Distance ◽  
Fatigue Tests ◽  
Evaluation Methodology ◽  
Element Analysis

Gas turbine blades mounted dovetail root are subjected to high centrifugal loads and gas forces. This situation causes low cycle fatigue (LCF). Recently, rotating speed and temperature of turbine rotor become higher in order to improve engine performance. To achieve this, it is required to evaluate accurate turbine blade’s LCF life of the contact surface between the blade dovetail root and the disk. However, the estimated blade lives using the peak stress calculated by finite element analysis (FEA) are much shorter than actual life because the stress at contact surface is excessively high. As a result, the blades are designed conservative and the blade’s weight tends to be heavy. Therefore, a more accurate evaluation methodology needs to be established. This study investigates the method to estimate the fatigue strength of dovetail using the theory of critical distance. The theory assumes that fatigue failures would occur due to the representative stress within a specific distance from stress concentration point. Fatigue tests and FEA for the turbine blade dovetail were conducted respectively in this research. The tests were carried out using single crystal nickel-based turbine blades at 600 °C and the fracture lives of dovetail were obtained. FEA was conducted to obtain the stress distributions at dovetail contact surface under testing condition. In this study, the critical distances of the single crystal nickel based alloy were obtained from the notched bar fatigue tests and FEA. Using these results and the theory of critical distance, fatigue lives of dovetail were obtained more accurately.

scholarly journals On the Fabrication of Metallic Single Crystal Turbine Blades with a Commentary on Repair via Additive Manufacturing

2020 ◽  
Vol 4 (4) ◽  
pp. 101
Author(s):  
Nicole Marie Angel ◽  
Amrita Basak
Keyword(s):  
Additive Manufacturing ◽  
Single Crystal ◽  
Production Process ◽  
Turbine Blades ◽  
Casting Process ◽  
Directionally Solidified ◽  
Material Loss ◽  
Manufacturing Defects ◽  
Process Failure ◽  
Traditional Manufacturing

The turbine section of aircraft engines (both commercial and military) is an example of one of the most hostile environments as the components in this section typically operate at upwards of 1650 °C in the presence of corrosive and oxidative gases. The blades are at the heart of the turbine section as they extract energy from the hot gases to generate work. The turbine blades are typically fabricated using investment casting, and depending on the casting complexity, they generally display one of the three common microstructures (i.e., equiaxed or polycrystalline, directionally solidified, and single crystal). Single crystal casting is exotic as several steps of the casting process are traditionally hands-on. Due to the complex production process involving several prototyping iterations, the blade castings have a significant cost associated with them. For example, a set of 40 single crystal turbine blades costs above USD 600,000 and requires 60–90 weeks for production. Additionally, if the components suffer from material loss due to prolonged service or manufacturing defects, the traditional manufacturing methods cannot restore the parent metallurgy at the damage locations. Hence, there is a significant interest in developing additive manufacturing (AM) technologies that can repair the single crystal turbine blades. Despite the blades’ criticality in aircraft propulsion, there is currently no review article that summarizes the metallurgy, production process, failure mechanisms, and AM-based repair methods of the single crystal turbine blades. To address this existing gap, this review paper starts with a discussion on the composition of the single crystal superalloys, describes the traditional fabrication methods for the metallic single crystal turbine blades, estimates the material and energy loss when the blades are scrapped or reverted, and provides a summary of the AM technologies that are currently being investigated for their repair potential. In conclusion, based on the literature reviewed, this paper identifies new avenues for research and development approaches for advancing the fabrication and repair of single crystal turbine blades.

scholarly journals Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

2000 ◽  
Author(s):  
Nagaraj K. Arakere ◽  
Gregory Swanson
Keyword(s):  
Fatigue Life ◽  
Single Crystal ◽  
Turbine Blade ◽  
Fatigue Failure ◽  
Failure Criterion ◽  
Crystal Orientation ◽  
Rocket Engine ◽  
Maximum Shear Stress ◽  
Turbine Blades ◽  
Fe Model

High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE’ N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude [Δτmax] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale 3D finite element (FE) model. This FE model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297 FE model runs. Fatigue lives at critical points in the blade are computed using FE stress results and the failure criterion developed. Stress analysis results in the blade attachment region are also presented. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to significantly increase a component’s resistance to fatigue crack growth without adding additional weight or cost.

scholarly journals Aero Engine Test Experience With CMSX-4® Alloy Single Crystal Turbine Blades

1994 ◽  
Author(s):  
Keith P. L. Fullagar ◽  
Robert W. Broomfield ◽  
Mark Hulands ◽  
Ken Harris ◽  
Gary L. Erickson ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Single Crystal ◽  
Turbine Blade ◽  
Hot Corrosion ◽  
Turbine Blades ◽  
Casting Process ◽  
Creep Rupture ◽  
Coating Performance ◽  
Turbine Engine ◽  
Mechanical Fatigue

A team approach involving a turbine engine company [Rolls-Royce], its single crystal casting facilities and a superalloy developer and ingot manufacturer [Cannon-Muskegon], utilizing the concepts of simultaneous engineering, has been used to successfully develop CMSX-4 alloy for turbine blade applications. CMSX-4 alloy is a second generation nickel-base single crystal superalloy containing 3% (wt) rhenium (Re) and 70% volume fraction of the coherent γ′ precipitate strengthening phase. Its finely balanced composition offers an attractive range of properties for turbine airfoil applications. In particular the alloy’s combination of high strength in relation to creep-rupture, mechanical and thermal fatigue, good phase stability following extensive high temperature, stressed exposure and oxidation, hot corrosion and coating performance, are attractive for turbine engine applications where engine performance and turbine airfoil durability are of prime importance. The paper details the single crystal casting process and heat treatment manufacturing development for turbine blades in CMSX-4 alloy. Competitive single crystal casting yields are being achieved in production and extensive vacuum heat treatment experience confirms CMSX-4 alloy to have a practical production solution heat treat / homogenization “window”. The creep-rupture data-base on CMSX-4 alloy now includes 325 data points from seventeen heats including fourteen 3630 kg (8000 lb) production size heats. An appreciable portion of this data was machined-from-blade (MFB) properties which indicate turbine blade component capabilities based on single crystal casting process, component configuration and heat treatment. The use of hot-isostatic-pressing (HIP) has been shown to eliminate single crystal casting micropores which along with the essential absence of γ/γ′ eutectic phase, carbides, stable oxide, nitride and sulphide inclusions results in remarkably high mechanical fatigue properties, with smooth and particularly notched specimens. The Re addition has been shown to not only benefit creep and mechanical fatigue strength (with and without HIP), but also bare oxidation, hot corrosion (sulphidation) and coating performance. The high level of balanced properties determined by extensive laboratory evaluation has been confirmed during engine testing the Rolls-Royce Pegasus turbofan.

Two Methods of Studying Structure Perfection of Single Crystal Nickel-Based Superalloys

2013 ◽  
Vol 203-204 ◽  
pp. 177-180 ◽  
Author(s):  
Arkadiusz Onyszko ◽  
Jan Sieniawski ◽  
Włodzimierz Bogdanowicz ◽  
Hans Berger
Keyword(s):  
Single Crystal ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Vacuum Furnace ◽  
Aerospace Materials ◽  
X Ray ◽  
University Of Technology ◽  
Assembly Structure ◽  
Development Laboratory ◽  
Laue Method

The article presents the comparison of two methods: classical X-ray topography and the modern automatic X-ray OD-EFG diffractometer. Both methods were applied to study the crystal orientation of turbine blades of single crystal nickel-based superalloys. The solidification of a hollow assembly structure for 5 various blades was carried out by the Bridgman method at the Research and Development Laboratory for Aerospace Materials at Rzeszow University of Technology using an ALD Vacuum Technologies vacuum furnace. Ceramic moulds made of Al2O3 were used. The alloy temperature during casting into the mould amounted to 1550°C. The specimens for Laue method tests were cut out from the blades at withdrawal rates of 1, 2, 3, 4, and 5 mm/min.

Strength Evaluation and Failure Prediction of a Composite Wind Turbine Blade Using Finite Element Analysis

2010 ◽  
Author(s):  
Prenil Poulose ◽  
Zhong Hu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Failure Prediction ◽  
Element Model ◽  
Wind Turbine Blade ◽  
Element Analysis ◽  
Strength Evaluation

Strength evaluation and failure prediction on a modern composite wind turbine blade have been conducted using finite element analysis. A 3-dimensional finite element model has been developed. Stresses and deflections in the blade under extreme storm conditions have been investigated for different materials. The conventional wood design turbine blade has been compared with the advanced E-glass fiber and Carbon epoxy composite blades. Strength has been analyzed and compared for blades with different laminated layer stacking sequences and fiber orientations for a composite material. Safety design and failure prediction have been conducted based on the different failure criteria. The simulation error estimation has been evaluated. Simulation results have shown that finite element analysis is crucial for designing and optimizing composite wind turbine blades.

scholarly journals The Microstructure, Mechanical Properties and Coatability of Diffusion Brazed CMSX-4 Single Crystal

1996 ◽  
Author(s):  
Warren M. Miglietti ◽  
Ros C. Pennefather
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Elevated Temperatures ◽  
Aluminide Coating ◽  
Turbine Blades ◽  
Stress Rupture ◽  
Directionally Solidified ◽  
Diffusion Brazing ◽  
Brazed Joints ◽  
Boride Phases

Diffusion brazing is a joining process utilized both in the manufacture and repair of turbine blades and vanes. CMSX-4 is an investment cast, single crystal, Ni-based superalloy used for turbine blading and vanes, and has enhanced mechanical properties at elevated temperatures when compared to equiaxed, directionally solidified and first generation single crystal superalloys. The objective of this work was to develop a diffusion brazing procedure to achieve reliable joints in the manufacture of a hollow turbine blade (for a prototype engine in South Africa), and to verify the coatability of the diffusion brazed joints. Two commercially available brazing filler metals of composition Ni-15Cr-3.5B and Ni-7Cr-3Fe-4.5Si-3.2B-0.06C and a proprietary (wide gap) braze were utilized. With the aim of eliminating brittle centre-line boride phases, the effects of temperature and time on the joint microstructure were studied. Once the metallurgy of the joint was understood, tensile and stress rupture tests were undertaken, the latter being one of the severest tests to evaluate joint strength. The results demonstrated that the diffusion brazed joints could satisfy the specified stress rupture criterion of a minimum of 40 hrs life at 925 °C and 200 MPa. After mechanical property evaluations, an investigation into the effects of a low temperature high activity (LTHA) pack aluminide coating and a high temperature low activity (HTLA) pack aluminide coating on the braze joints was undertaken. The results showed that diffusion brazed joints could be readily coated.

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