The effects of solution treatment on the microstructure of the cast Ni-based IN100 superalloy

A Jafari,M Seifollahi,S M Abbasi,M Morakabati,A Rahimi

doi:10.30544/78

Abstract

In this research, the effects of the partial, full and partial + full solution heat treatments followed by aging at 900 °C for 10 h, on the microstructure of cast Ni-based IN100 superalloy were assessed. It has been found that, the alloy in the partial + full solution treated condition had the optimal combination of γ’ morphology, volume fraction and size. In this condition, the alloy possesses a cubic primary γ’with an average size of 470±10nm and 45% volume fraction. Discrete M23C6 and M6C carbides were formed at the grain boundaries and the morphology of the cubic MC carbide was changed to the spherical shape. In addition, the volume fraction of γ’/γ eutectic phase dropped to half of its value, compared to the as-cast alloy. During partial solution treatment followed by aging, discrete carbides were formed at the grain boundaries. This treatment without full solutioning was not an effective method to provide an optimal volume fraction and arrangement of γ’ and MC carbides morphology. Full solutioning alone, changed the cubic morphology of the primary γ’ and the blocky MC carbides to the spherical shape.

Highlights

IN100 is a nickel-based superalloy widely used in the gas turbine industry such as blades and nozzles
A suitable solution and aging heat treatment can improve the mechanical properties of IN100 alloy through the following events: increasing the γ’ volume fraction and optimizing its morphology, the modification of MC carbides morphology, the precipitation of M6C and M23C6 carbides, and reducing solidification segregations and γ’/γ eutectic phase [9]
The alloy was remelted in an electro-slag remelting (ESR) furnace to improve homogeneity and reduce impurities such as sulphur and inclusions

Summary

Introduction

IN100 is a nickel-based superalloy widely used in the gas turbine industry such as blades and nozzles. Volume fraction of γ’, shows the excellent microstructural stability and mechanical properties at moderately high temperature. Minor phases such as carbide and γ’/γ eutectic have been identified in the alloy and may be detrimental to mechanical properties. Blocky Ti-rich MC carbides are formed during solidification and distributed into the γ matrix between the dendritic cells and at the grain boundaries [5]. A suitable solution and aging heat treatment can improve the mechanical properties of IN100 alloy through the following events: increasing the γ’ volume fraction and optimizing its morphology, the modification of MC carbides morphology, the precipitation of M6C and M23C6 carbides, and reducing solidification segregations and γ’/γ eutectic phase [9]. In the present work, the microstructure of the alloy, including γ’phases, carbides and γ’/γ eutectic phase, is evaluated after various solution treatment cycles

Experimental procedure

Results and discussion

Conclusions