Simulation and Experimental Studies on Grain Selection and Structure Design of the Spiral Selector for Casting Single Crystal Ni-Based Superalloy

Hang Zhang,Qingyan Xu

doi:10.3390/ma10111236

Abstract

Grain selection is an important process in single crystal turbine blades manufacturing. Selector structure is a control factor of grain selection, as well as directional solidification (DS). In this study, the grain selection and structure design of the spiral selector were investigated through experimentation and simulation. A heat transfer model and a 3D microstructure growth model were established based on the Cellular automaton-Finite difference (CA-FD) method for the grain selector. Consequently, the temperature field, the microstructure and the grain orientation distribution were simulated and further verified. The average error of the temperature result was less than 1.5%. The grain selection mechanisms were further analyzed and validated through simulations. The structural design specifications of the selector were suggested based on the two grain selection effects. The structural parameters of the spiral selector, namely, the spiral tunnel diameter (dw), the spiral pitch (hb) and the spiral diameter (hs), were studied and the design criteria of these parameters were proposed. The experimental and simulation results demonstrated that the improved selector could accurately and efficiently produce a single crystal structure.

Highlights

Single crystal blades have been widely utilized in aviation and energy, due to the corresponding superior high-temperature performance
In the seed crystal method, a specific orientation seed is placed at the bottom of the casting shell, where the seed grows through the deposition of metal atoms during directional solidification (DS), producing a single crystal structure
(1) Thermal transfer and microstructure models based on Cellular automaton-Finite difference (CA-FD) were built to simulate the temperature variation and microstructure evolution in the spiral selector during the single temperature variation and microstructure evolution in the spiral selector during the single crystal superalloy casting

Summary

Introduction

Single crystal blades have been widely utilized in aviation and energy, due to the corresponding superior high-temperature performance. In the seed crystal method, a specific orientation seed is placed at the bottom of the casting shell, where the seed grows through the deposition of metal atoms during DS, producing a single crystal structure. In this method, a fusion zone exists between the melt and the seed crystal. The grain growth region transitions from unsteady self-organization to steady-state growth, as well as the solidification behavior are affected by additional factors. This process is hard to control [3,4,5]. A spiral selector has a complex spatial structure, which creates a complex visibility relationship among the selector, the furnace heating

Methods

Results

Conclusion