Investigation of Start Block and Corresponding Influence for Grain Selection during Casting of Single-Crystal Superalloys.

Xintao Zhu,Michael Mathes,Andreas Bührig-Polaczek,Dexin Ma,Tobias Wittenzellner,Fu Wang,Susanne Hemes,Shuaipeng Zhang

doi:10.3390/ma12101717

Xintao Zhu, Michael Mathes + Show 6 more

Open Access

https://doi.org/10.3390/ma12101717

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Journal: Materials	Publication Date: May 27, 2019
Citations: 2	License type: CC BY 4.0

Affiliation: RWTH Aachen University, Access, Xi'an Jiaotong University

Abstract

To figure out the impact of the parameters of a starter block (the diameter D and height H) on grain selection and the selecting mechanism, a spiral selector was measured with optical microscopy (OM) and electron backscatter diffraction (EBSD) during the solidification of Ni-based single crystal (SX) superalloys. In this experiment, starter blocks with diameters of 8 mm, 10 mm, 15 mm, and 30 mm and a height of 30 mm were designed to find the best parameters. Recommendations for optimizing starter block geometry are provided.

Highlights

Superalloys are a series of materials with high alloying strength and great surface stability with a Nickel or Cobalt matrix
According to the electron backscatter diffraction (EBSD) results, When the heat transfer between the chill plate and the molten metal causes the temperature to reach at the bottom of the starter block, the average orientation deviation of the four different below the liquidus of the alloy, the molten metal nucleates at the bottom of the seeding section to form diameter grains is above 20 degrees, and the diameter has little effect on the chilling nucleation of the an equiaxed crystal with different orientations from each other
The majority of the grain orientations in the whole selecting process was optimized in the starter block, and only a couple of grains with well-aligned orientations through competitive growth can enter the selector

Summary

Introduction

Superalloys are a series of materials with high alloying strength and great surface stability with a Nickel or Cobalt matrix. Prior studies [6,7,8,9] suggested that the function of the starter block is to optimize the grain orientation. Both of reduction the diameter of the starter of block theblock increase theincrease height can improve the of the diameter the and starter andinthe in the heightthe canoptimization improve theof the orientation that the deflection angle of the grains is the small and is the finaland single optimization of the soorientation so that the deflection angle of grains small the crystal final can be selected.

Casting

H5HCl using

Results and Discussion

Diagrams andnumber inverse pole at in different heights width

Conclusions