Development of Low-Cost Polycrystalline Nickel-Base Superalloys for Gas Turbine Applications
type: CreativeWork
description: Polycrystalline nickel-base superalloys have found extensive application throughout the aerospace, petrochemical and power generation sectors, due to their exceptional balance of high temperature mechanical properties, thermal stability and oxidation resistance. Extensive alloy development has produced a diverse class of alloys suited to a wide range of operating conditions. This work details research performed to develop new low-cost polycrystalline Ni-base superalloys, intended for intermediate temperature and loading environments. There is currently significant industrial demand for alloys of this type, that offer improved thermal stability and mechanical properties compared to current commercial alloys such as Inconel 718 and ATI 718Plus, whilst retaining good amenability to deformation processing and joining operations. The important properties required of polycrystalline Ni-base superalloys are discussed alongside an initial comparison of current commercially available materials and a potential class of candidate alloys suitable for further development. Compositional modifications were made to these alloys in order to improve their thermal stability and reduce their cost. Characterisation was performed after a standard ageing heat treatment, and after long term thermal exposure at 700˚C, revealing significantly improved resistance to precipitation of the δ phase in these alloys compared to Inconel 718. Despite this, comparable measurements of the hardness values indicated similar mechanical strength. The oxidation resistance of the candidate alloys was also assessed through 1000~hour exposures in air at 700˚C and 800˚C. The alloys were found to be chromia forming, with internal oxidation of Al forming a discontinuous subscale. Significant microstructural degradation was observed at 800˚C due to the formation of the δ phase, with the differences in oxidation behaviour rationalised using Wagnerian diffusional analyses. So that further investigation of fundamenta…
abstract: Polycrystalline nickel-base superalloys have found extensive application throughout the aerospace, petrochemical and power generation sectors, due to their exceptional balance of high temperature mechanical properties, thermal stability and oxidation resistance. Extensive alloy development has produced a diverse class of alloys suited to a wide range of operating conditions. This work details research performed to develop new low-cost polycrystalline Ni-base superalloys, intended for intermediate temperature and loading environments. There is currently significant industrial demand for alloys of this type, that offer improved thermal stability and mechanical properties compared to current commercial alloys such as Inconel 718 and ATI 718Plus, whilst retaining good amenability to deformation processing and joining operations. The important properties required of polycrystalline Ni-base superalloys are discussed alongside an initial comparison of current commercially available materials and a potential class of candidate alloys suitable for further development. Compositional modifications were made to these alloys in order to improve their thermal stability and reduce their cost. Characterisation was performed after a standard ageing heat treatment, and after long term thermal exposure at 700˚C, revealing significantly improved resistance to precipitation of the δ phase in these alloys compared to Inconel 718. Despite this, comparable measurements of the hardness values indicated similar mechanical strength. The oxidation resistance of the candidate alloys was also assessed through 1000~hour exposures in air at 700˚C and 800˚C. The alloys were found to be chromia forming, with internal oxidation of Al forming a discontinuous subscale. Significant microstructural degradation was observed at 800˚C due to the formation of the δ phase, with the differences in oxidation behaviour rationalised using Wagnerian diffusional analyses. So that further investigation of fundamenta…
author: Wise, George
language: eng
keywords: Forging, Gas Turbines, Metallurgy, Microstructure, Ni-base Superalloys, Oxidation, Precipitation, Recrystallisation, Welding
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/9a1d672d-322a-4ecd-8a2b-45a1c1a824d1/download
license: http://purl.org/NET/rdflicense/allrightsreserved
date published: 2023-02-17
date modified: 2026-07-22T22:24:16Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.96551