scholarly journals Multiscale Modeling and Simulation of Directional Solidification Process of Ni-Based Superalloy Turbine Blade Casting

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 632 ◽  
Author(s):  
Qingyan Xu ◽  
Cong Yang ◽  
Hang Zhang ◽  
Xuewei Yan ◽  
Ning Tang ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Grain Growth ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Solidification Process ◽  
Experimental Results ◽  
Directional Solidification Process ◽  
Grain Structures ◽  
Aero Engine ◽  
Engine Blade

Ni-based superalloy turbine blades have become indispensable structural parts in modern gas engines. An understanding of the solidification behavior and microstructure formation in directional solidified turbine blades is necessary for improving their high-temperature performance. The multiscale simulation model was developed to simulate the directional solidification process of superalloy turbine blades. The 3D cellular automaton-finite difference (CA-FD) method was used to calculate heat transfer and grain growth on the macroscopic scale, while the phase-field method was developed to simulate dendrite growth on the microscopic scale. Firstly, the evolution of temperature field of an aero-engine blade and a large industrial gas turbine blade was studied under high-rate solidification (HRS) and liquid-metal cooling (LMC) solidification processes. The varying withdrawal velocity was applied to change the curved mushy zone to a flat shape. Secondly, the grain growth in the aero-engine blade was simulated, and the grain structures in the starter block part and the spiral selector part in the HRS process were compared with those in the LMC process. The simulated grain structures were generally in agreement with experimental results. Finally, the dendrite growth in the typical HRS and LMC solidification process was investigated and the simulation results were compared with the experimental results in terms of dendrite morphology and primary dendritic spacing.

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.

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.

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