Grain Orientation Optimization of Two-Dimensional Grain Selector during Directional Solidification of Ni-Based Superalloys.

Xintao Zhu,Fu Wang,Qiang Yang,Dexin Ma

doi:10.3390/ma13051121

Xintao Zhu, Fu Wang + Show 2 more

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https://doi.org/10.3390/ma13051121

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Abstract

The grain selection method is widely used in industry to produce Ni-based single crystal superalloys. A Z-form two-dimensional (2D) grain selector was designed to obtain high-quality single crystals. To control grain orientation deviation, one of the most important defects of the single crystal superalloys in casting, Z-form 2D grain selectors with different take-off angle were investigated in this study. The MM247LC superalloy single crystal samples were obtained by the Bridgman method modified by the Z-form grain selectors in this study. The Electron Backscattered Diffraction (EBSD) and the Optical Microscopy (OM) were used to observe and measure the grain selection growth and the microstructural evolution and orientation of the single crystal were also discussed. The results show that a Z-form 2D grain selector with an appropriate take-off angle can significantly reduce the deviation of the grain orientation. A single crystal superalloy with a deviation angle less than 6° can be obtained effectively when the take-off angle was 40°.

Highlights

Jet engine turbine blades are located in the harsh environment behind the burner and rotate at high speed to extract energy from the high-temperature gas stream
Case 1, Case 2 and Case 3 with the take-off angle of 15◦, 30◦ and 40◦, respectively, while stray grains exist in the grain selectors with take-off angle larger than 40◦
It can be seen that the take-off angle of 2D grain selector has a direct effect on the single crystal growth

Summary

Introduction

Jet engine turbine blades are located in the harsh environment behind the burner and rotate at high speed to extract energy from the high-temperature gas stream. Ni-based superalloy is usually used in the gas turbine to optimize its functions and to perform the roles of energy conservation, emission reduction and environmental protection [1,2,3]. Wretland and Polvorosa proposed a method to improve the properties of alloy by refining grain [4,5]. Ni-based single crystal (SX) superalloy turbine blades have been widely used in jet engines and power generation for their endurance under high service temperature, their thermomechanical fatigue properties, and their creep performance [6,7,8,9,10,11].

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