Influences of a Hot-Working Process on the Microstructural Evolution and Creep Performance of a Spray-Formed Nickel-Based Superalloy

Tian Tian,Chonglin Jia,Zhibo Hao,Xinggang Li,Changchun Ge,Shiqing Peng

doi:10.3390/met10040454

Abstract

A new third generation nickel-based powder metallurgy (PM) superalloy, designated as FGH100L, was prepared by spray forming. The effects of hot isostatic pressing (HIP) and isothermal forging (IF) processes on the creep performance, microstructure, fracture, and creep deformation mechanism of the alloy were studied. The microstructure and fracture were characterized by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The coupled HIP and IF process improved the creep performance of the alloy under the creep condition of 705 °C/897 MPa. As for both the HIPed and IFed alloys, the creep process was dominated by the accumulation of dislocations and stacking faults, cutting through γ′ precipitates. The microstructural evolution was the main factor affecting the creep performance, which mainly manifested as coarsening, splitting, and morphology change of γ′ precipitates. Both the creep fractures of the HIPed and IFed alloys indicated intergranular fracture characteristics. In the former, wedge-shaped cracks usually initiated at the trigeminal intersection of the grain boundaries, while in the latter, cavity cracks generate more easily around the serrated curved grain boundary and carbides.

Highlights

The nickel-based powder metallurgy (PM) superalloys are of the most important materials for manufacturing turbine disks of advanced aeroengines
The creep curve can be divided into three stages: the primary creep stage, the secondary stage of steady-state creep, and the tertiary stage of accelerated creep
No distinct primary creep stage can be observed in the creep curves, and the secondary and tertiary stages predominate in these curves

Summary

Introduction

The nickel-based powder metallurgy (PM) superalloys are of the most important materials for manufacturing turbine disks of advanced aeroengines. The failure of most load-bearing components under the condition of high temperature and high pressure is caused by high-temperature creep [1], which can lead to excessive plastic deformation or creep fracture of aeroengine parts. There has been a lot of research work on the creep deformation mechanisms of nickel-based superalloys. The turbine disk of aeroengine can work continuously for hundreds to thousands of hours at 650–750 ◦ C during its service. It is predicted that the service temperature requirements of the high-pressure compressor and turbine disk of an aeroengine may rise to over 750–800 ◦ C in the future. It is necessary to develop high temperature materials that can withstand higher temperature and have better creep and oxidation resistance. It is necessary to continuously improve the preparation process of Metals 2020, 10, 454; doi:10.3390/met10040454 www.mdpi.com/journal/metals

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