Significant Improvement of Strength in Wrought 945A Ni-Based Superalloy by Aging Treatment

Haiding Liu,Jia She,Dongzhe Wang,Wei Wu,Linping Zhou

doi:10.3390/cryst11060627

Abstract

Ni-based superalloys have attracted much attention due to their good resistance to high-temperature and -pressure environments. Compared with the traditional 718 Ni-based superalloy, 945A Ni-based superalloy with a lower Ni content showed better performance in terms of precipitated hardening and corrosion resistance. In this study, the aging behavior and the evolution of mechanical properties of the wrought 945A Ni-based superalloy were investigated. Microstructures were analyzed by scanning electron microscopy (SEM), bright field transmission electron microscopy (TEM), high-resolution TEM and high-angle annular dark field scanning TEM. Mechanical properties were measured by tensile and compressive tests. The results illustrated that the compressive yield stress was significantly improved by increasing aging time from 229 to 809 MPa. The increase was greater than 220%. This improvement was mainly attributed to the precipitates of the γ′ phase and carbides during the aging treatment. The residual dislocations generated by the plastic processes stimulated the formation of these precipitates. The precipitation behavior and the strengthening mechanism are discussed in detail.

Highlights

Ni-based superalloys are one type of metal alloy for application in harsh conditions, such as high-temperature, high-pressure and corrosive environments [1,2]
A similar distribution was found in an investigation of ATI 718Plus [23], which was aged at a different temperature (675 ◦ C for 8 h and 788 ◦ C for 4 h)
The aging behavior of the wrought 945A Ni-based superalloy was investigated at 725 ◦ C with different aging durations

Summary

Introduction

Ni-based superalloys are one type of metal alloy for application in harsh conditions, such as high-temperature, high-pressure and corrosive environments [1,2]. Compared with the traditional Inconel 718 superalloy, Incoloy 945A superalloy with a lower Ni content (≈47 wt.%) is a precipitated hardening and corrosion-resistant Ni-Fe-Cr alloy, which presents excellent strength, ductility and resistance to corrosion cracking [3]. Similar to the traditional 718 Inconel superalloy, the matrix of 945A superalloy is a face centered cubic (FCC) structure known as gamma (γ) phase. The main second phases of the 945A superalloy are γ0 (Ni3 (Al, Ti, Nb)) and γ00 (Ni3 Nb) [4]. The second phases can be obtained by using different heat-treatment processes. The γ0 phase presents an A3 B type, in which ‘A’ is the Ni element and ‘B’ can be replaced by

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Conclusion