Characterization of Microstructure, Precipitations and Microsegregation in Laser Additive Manufactured Nickel-Based Single-Crystal Superalloy.

Zhaoyang Liu,Jiayang Shu

doi:10.3390/ma13102300

Abstract

In this study, the microstructure, precipitations, and microsegregation in the laser additive manufactured thin-wall structure of a single-crystal superalloy are synthetically characterized. The influence of a subsequent heat treatment on the microstructure and precipitations is discussed. The results show that under the given processing conditions, the single-crystal microstructure is regenerated perfectly with small misorientation angles in the thin-wall structure. The crystal morphology shows obvious diversity and instability with the incremental height of thin-wall structure. With the increase of manufacturing height, both the primary and secondary dendritic arm spacings of epitaxial columnar dendrites first increase rapidly and then reach a dynamic balanced state. The distribution of precipitations and pores keeps symbiosis in the interdendritic region and shows periodic band characteristic with high density in the band region and low density in the inner region of plate layers. The microsegregation of element atoms in the microstructure shows a three-dimensional network distribution. The concentration of element atoms keeps good consistency with high value in the three-dimensional network and nearly standard value in the outside region. The subsequent heat treatment process contributes to the occupation of as-processed pores by the expanded mature precipitations with good blocky shape. Further optimization of the heat treatment process for improving the lattice coherency of precipitated γ’ phase and γ matrix in the laser additive manufactured single-crystal superalloy is needed and valuable.

Highlights

To meet the rapidly increasing demand of raising the fuel efficiency of gas turbine engines, the high-temperature turbine blades with nickel-based single-crystal (SX) superalloy have been widely used to elevate the combustion chamber working temperature [1,2]
The subsequent heat treatment process contributes to the occupation of as-processed pores by the expanded mature precipitations with good blocky shape
A common one is the tip material loss resulting from the abrasion between blades and engine shroud

Summary

Introduction

To meet the rapidly increasing demand of raising the fuel efficiency of gas turbine engines, the high-temperature turbine blades with nickel-based single-crystal (SX) superalloy have been widely used to elevate the combustion chamber working temperature [1,2]. The monocrystalline nature of SX turbine blades supports superior high-temperature mechanical properties and simultaneously causes high crack susceptibility [3,4]. During the long service in the combustor, the lifespan of SX turbine blades is restricted by various unavoidable defects [5,6]. A common one is the tip material loss resulting from the abrasion between blades and engine shroud. Once the tip material loss reaches a certain amount, the blades need to be replaced. Within each aero-engine containing many high value

Methods

Results

Conclusion