Modeling of Unidirectional Growth in a Single Crystal Turbine Blade Casting

2006 ◽  
Vol 508 ◽  
pp. 111-116 ◽  
Author(s):  
Qing Yan Xu ◽  
Bai Cheng Liu ◽  
Zuo Jian Liang ◽  
Jia Rong Li ◽  
Shi Zhong Liu ◽  
...  
Keyword(s):  
Single Crystal ◽  
Directional Solidification ◽  
Turbine Blade ◽  
Defect Formation ◽  
Turbine Blades ◽  
Solidification Process ◽  
Nickel Base Superalloy ◽  
Transversal Section ◽  
Nickel Base ◽  
Blade Casting

Single crystal superalloy turbine blade are widely used in aero-engineering. However, there are often grain defects occurring during the fabrication of blade by casting. It is important to study the formation of microstructure related defects in turbine blades. Single crystal blade sample castings of a nickel-base superalloy were produced at different withdrawal rates by the directional solidification process and investment casting. There was a difference between the microstructure morphology at the top part of the turbine blade sample castings and the one at the bottom. Higher withdrawal rates led to more differences in the microstructure and a higher probability of crystallographic defect formation such as high angle boundaries at locations with an abrupt change of the transversal section area. To further investigate the formation of grain defects, a numerical simulation technique was used to predict the crystallographic defects occurring during directional solidification. The simulation results agreed with the experimental ones.

scholarly journals Thermal–Fluid–Solid Coupling Analysis on the Temperature and Thermal Stress Field of a Nickel-Base Superalloy Turbine Blade

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3315
Author(s):  
Liuxi Cai ◽  
Yao He ◽  
Shunsen Wang ◽  
Yun Li ◽  
Fang Li
Keyword(s):  
Thermal Stress ◽  
Temperature Gradient ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Nickel Base Superalloy ◽  
Barrier Coating ◽  
Thermal Stress Field ◽  
Nickel Base ◽  
Stress Damage ◽  
Superalloy Turbine Blade

Based on the establishment of the original and improved models of the turbine blade, a thermal–fluid–solid coupling method and a finite element method were employed to analyze the internal and external flow, temperature, and thermal stress of the turbine blade. The uneven temperature field, the thermal stress distribution characteristics of the composite cooling turbine blade under the service conditions, and the effect of the thickness of the thermal barrier coating (TBC) on the temperature and thermal stress distributions were obtained. The results show that the method proposed in this paper can better predict the ablation and thermal stress damage of turbine blades. The thermal stress of the blade is closely related to the temperature gradient and local geometric structure of the blade. The inlet area of the pressure side-platform of the blade, the large curvature region of the pressure tip of the blade, and the rounding between the blade body and the platform on the back of the blade are easily damaged by thermal stress. Cooling structure optimization and thicker TBC thickness can effectively reduce the high temperature and temperature gradient on the surface and inside of the turbine blade, thereby reducing the local high thermal stress.

Influence of an Aluminide Coating on the TMF Life of a Single Crystal Nickel-Base Superalloy

1998 ◽  
Author(s):  
Ernst E. Affeldt
Keyword(s):  
Single Crystal ◽  
Aluminide Coating ◽  
Turbine Blades ◽  
Temperature Cycling ◽  
Nickel Base Superalloy ◽  
Test Results ◽  
Bending Tests ◽  
Quantitative Correlation ◽  
Nickel Based Superalloy ◽  
Nickel Base

TMF tests were conducted with bare and aluminide coated single crystal nickel-based superalloy specimens. Temperature cycling was between 400°C and 1100°C with a phase shift (135°) which is typical for damaged locations on turbine blades. Stress response is characterized by a constant range and the formation of a tensile mean stress as a result of relaxation in the high temperature part of the cycle which is in compression. Bare specimens showed crack initiation from typical oxide hillocks. Coated specimens showed life reduction with respect to the bare ones caused by brittle cracking of the coating in the low temperature part of the cycle. Isothermal bending tests of coated specimens confirmed the low ductility of the coating at tempeatures below 600°C but quantitative correlation with the TMF test results failed.

scholarly journals Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

2000 ◽  
Vol 123 (2) ◽  
pp. 413-423 ◽  
Author(s):  
Nagaraj K. Arakere ◽  
Gregory Swanson
Keyword(s):  
Single Crystal ◽  
Contact Stress ◽  
Crystal Orientation ◽  
Rocket Engine ◽  
Turbine Blades ◽  
Nickel Base Superalloy ◽  
Attachment Region ◽  
Nickel Base ◽  
Fatigue Failures ◽  
Base Superalloy

Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. High cycle fatigue induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate advanced high pressure fuel turbo pump for the space shuttle main engine. Single crystal materials have highly anisotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale three-dimensional finite element model capable of accounting for contact friction, material anisotropy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation. Fretting stresses at the attachment region are seen to vary significantly as a function of crystal orientation. The stress variation as a function of crystal orientation is a direct consequence of the elastic anisotropy of the material. Fatigue life calculations and fatigue failures are discussed for the airfoil and the blade attachment regions.

The Precipitation Behavior of γ′ Phase in Single Crystal Ni-Based DD6 Superalloy for Turbine Blade

2017 ◽  
Vol 898 ◽  
pp. 534-544
Author(s):  
Y.P. Xue ◽  
Jia Rong Li ◽  
Jin Qian Zhao ◽  
J.C. Xiong
Keyword(s):  
Single Crystal ◽  
Directional Solidification ◽  
Turbine Blade ◽  
Solidification Process ◽  
Isothermal Solidification ◽  
Single Crystal Superalloy ◽  
Size Difference ◽  
Precipitation Behavior ◽  
Cooling Rates ◽  
Directional Solidification Process

The precipitation behavior of γ′ precipitates in typical section dimensions of DD6 single crystal superalloy turbine blade was investigated experimentally during directional solidification process. The phase transformation temperatures in the single crystal Ni-based DD6 superalloy from DSC analysis and JmatPro simulation were basically in consistent with the isothermal solidification experiments. The solidification route of DD6 single crystal superalloy could be described as follows: L1 → γ + L2; L2 → (γ + γ′)eutectic + MC; γ → γ′/γ. With increasing continuous cooling rates, the primary γ′ precipitates tended to be refined, and the size distributions of the primary γ′ precipitates at every temperature measuring position followed the normal distribution. In comparison to the interdendritic regions, nearly a 60% reduction in the average sizes of the primary γ′ precipitates was measured in the dendritic core regions. The result of the primary γ′ size difference was strongly affected by the multi-component segregations between the interdendritic and dendritic regions, where the γ′ forming elements of Al and Ta segregated towards the interdendritic regions. Furthermore, the secondary γ′ precipitation was found to occur within a relatively wide corridor of γ matrix for low cooling rates (12.6, 23.3 and 29.7 °C/min) during the directional solidification process. The occurrence of the secondary γ′ precipitation resulted from the complex interaction of multiple thermodynamic and kinetic factors in the γ′ nucleation and the diffusion rate of γ′ forming elements.

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