Precipitation Behavior of the Topologically Close-Packed Phase in the DD5 Superalloy during Long-Term Aging.

Guiqun Liu,Yanxin Qiao,Xinyi Wang,Xiaoli Zhang

doi:10.1155/2020/2569837

Abstract

The precipitation behaviors of the topologically close-packed (TCP) phases in the bicrystal DD5 superalloy have been investigated. The results showed that the [001] crystallographic orientations are consistent with that of adjacent grains; however, the direction of the needle-like TCP phases is not consistent with that of the γ phase channels. The angle between needle-like TCP phases and γ phase channels is 45°, but the angle between the needle-like TCP phases of the adjacent grains is equal to the misorientation of the adjacent grains. Furthermore, during long-term aging, the needle-like TCP phases gradually decompose and transform into globular and short rod-like phases. The TCP phases precipitate preferentially in the dendrite. It is difficult to precipitate at the interdendrite/grain boundary, which is caused by the segregation of the constituent elements of the TCP phase to the dendrite.

Highlights

Superalloy is a kind of high-alloying iron-based, nickelbased, or cobalt-based metal material, which can withstand large complex stress above 600°C and has certain surface stability [1]
In order to continuously improve its high temperature creep resistance, more and more refractory elements have been added to the superalloy
The addition of excessive alloy elements such as Cr, Mo, W, and Re to the superalloy will cause the precipitation of intermetallic phases which have complex crystal structures rich in these refractory elements during long-term heat exposure or service

Summary

Introduction

Superalloy is a kind of high-alloying iron-based, nickelbased, or cobalt-based metal material, which can withstand large complex stress above 600°C and has certain surface stability [1]. The addition of excessive alloy elements such as Cr, Mo, W, and Re to the superalloy will cause the precipitation of intermetallic phases which have complex crystal structures rich in these refractory elements during long-term heat exposure or service. Because of their special dense structures, these phases are generally referred to as the topologically close-packed (TCP) phase [2]. The TCP phase in the second-generation Ni-based superalloy DD5 is studied and the precipitation and evolution of the TCP phase are found and summarized It provides evidence for further understanding the precipitation behavior and characteristics of the TCP phase in Ni-based single-crystal superalloys

Materials and Methods

Results and Discussions

Conclusions