Understanding, Developing and Exploiting Cobalt Superalloys for Discs
Lead Research Organisation:
Imperial College London
Department Name: Materials
Abstract
In 2005, the discovery of a new intermetallic was announced in Science, Co3(Al,W), together with evidence Co-Co3(Al,W) alloys might have a higher temperature capability than in the Ni-base superalloys used in jet engines. It was claimed that this would allow a new generation of gas turbine alloys to be developed beyond Ni-base superalloys.
However, these alloys and those developed since have densities that are too high and oxidation resistance that is too poor for engineering application. Over the past two years, as part of the Rolls Royce - EPSRC Strategic Partnership, two PhD students at Imperial College have demonstrated that a lower density, oxidation resistant Co-base superalloy can be developed, which still has a superior temperature capability.
The aim of the current work is to develop the underpinning science underlying the effect of alloying on the creep behaviour of these alloys, which is principally a function of the way in which deformation-related defects called dislocations move through the structure and in particular the way they interact with the intermetallic precipitate. Our recent work has demonstrated that this interface is not sharp and instead has a width that varies with alloying from 0.4 to over 2nm, a factor of over 5X. It is expected that this will increase the rate at which these intermetallic precipitates grow in size - from 20nm to over 200nm - in service, which in turn is a major driver for strength and creep resistance.
However, these alloys and those developed since have densities that are too high and oxidation resistance that is too poor for engineering application. Over the past two years, as part of the Rolls Royce - EPSRC Strategic Partnership, two PhD students at Imperial College have demonstrated that a lower density, oxidation resistant Co-base superalloy can be developed, which still has a superior temperature capability.
The aim of the current work is to develop the underpinning science underlying the effect of alloying on the creep behaviour of these alloys, which is principally a function of the way in which deformation-related defects called dislocations move through the structure and in particular the way they interact with the intermetallic precipitate. Our recent work has demonstrated that this interface is not sharp and instead has a width that varies with alloying from 0.4 to over 2nm, a factor of over 5X. It is expected that this will increase the rate at which these intermetallic precipitates grow in size - from 20nm to over 200nm - in service, which in turn is a major driver for strength and creep resistance.
Planned Impact
Knowledge - Scientific Advances and Techniques
Conventional nickel-base superalloys are mature yet their temperature capability is the fundamental limit on the efficiency that can be attained by gas turbines. Therefore developing and understanding a successor alloy system - the Co-base superalloys - will enable developments in other gas turbine technologies such as ceramic coatings, combustion research and the fluid-mechanical design of turbomachinery.
One of the major subthemes of this proposal is that it shows leadership of the community by integrating our recent technique developments to achieve scientific insight into a phenomena and to articulate its consequences.
Policy and Quality of Life
In helping to mitigate CO2 emissions, the work developed here will help forestall the consequences of global warming, having a global impact on emissions. With growth in the BRICs and North American emissions being such a large contributor to this global pollutant, even small improvements here are arguably more significant that any UK-centric initiatives, especially now that the UK government is becoming more focussed on shale gas.
In aerospace sustained competitive advantage is obtained by cumulative capabilities - deep experience of design, underpinning science and service support, and this is why the UK aerospace sector has remained competitive. The work here provides us with an opportunity to showcase this to the policy community, deepening its understanding of research translation.
This sort of safety-critical work will be of great interest to certification authorities such as the US AFRL, FAA and CAA. The results will therefore influence industry design and global turbofan certification practice, improving air safety for the travelling public.
Economy - inward investment, wealth creation, products and services
Manufacturing remains the third largest sector in the UK economy and has continued to grow. There is a clear trend in low value, high volume manufacturing moving to developing countries while in the UK the higher technology areas generate the better Gross Value Added returns. Aerospace is a global growth sector, contributing around 7.5% of global GDP, with traffic growing faster than the global economy (5-6% pa). Rolls Royce is the UK's largest export business with revenues of £11bn p.a., >75% of which is civil and exported, and over 40,000 employees, most of whom are in the UK.
Co superalloys promise a >100 C improvement in usable temperature capability. In the jet engine business, 0.5% engine fuel efficiency is worth around US$10m/yr in cost and CO2 to the airline per plane, and is the difference between success and failure for an engine programme, being proportional to approx. 10 C in turbine entry temperature. Clearly, success in this programme would provide a sustained source of competitive advantage to Rolls Royce if successfully taken through the subsequent >£1m alloy qualification programme.
People - skills and people pipeline
UK metallurgy and STEM more generally continues to find recruitment problematic. Therefore with the rebalancing of UK attitudes away from financial services and towards manufacturing, it is currently timely to use research outcomes to evangelise society and especially teenagers to build the people pipeline.
However, the reach that individual research projects can have is necessarily limited. Therefore we engage with other projects that target teenagers to deliver this impact, such as the Naked Scientists and Exscitec.
The PDRAs employed will also provide people trained in mechanisms-based, linked alloy and fundamental science development, together with linked computational modelling for insight. With much excitement around ICME approaches and initiatives such as the US Materials Genome Initiative, people with this outlook will be in significant demand.
Conventional nickel-base superalloys are mature yet their temperature capability is the fundamental limit on the efficiency that can be attained by gas turbines. Therefore developing and understanding a successor alloy system - the Co-base superalloys - will enable developments in other gas turbine technologies such as ceramic coatings, combustion research and the fluid-mechanical design of turbomachinery.
One of the major subthemes of this proposal is that it shows leadership of the community by integrating our recent technique developments to achieve scientific insight into a phenomena and to articulate its consequences.
Policy and Quality of Life
In helping to mitigate CO2 emissions, the work developed here will help forestall the consequences of global warming, having a global impact on emissions. With growth in the BRICs and North American emissions being such a large contributor to this global pollutant, even small improvements here are arguably more significant that any UK-centric initiatives, especially now that the UK government is becoming more focussed on shale gas.
In aerospace sustained competitive advantage is obtained by cumulative capabilities - deep experience of design, underpinning science and service support, and this is why the UK aerospace sector has remained competitive. The work here provides us with an opportunity to showcase this to the policy community, deepening its understanding of research translation.
This sort of safety-critical work will be of great interest to certification authorities such as the US AFRL, FAA and CAA. The results will therefore influence industry design and global turbofan certification practice, improving air safety for the travelling public.
Economy - inward investment, wealth creation, products and services
Manufacturing remains the third largest sector in the UK economy and has continued to grow. There is a clear trend in low value, high volume manufacturing moving to developing countries while in the UK the higher technology areas generate the better Gross Value Added returns. Aerospace is a global growth sector, contributing around 7.5% of global GDP, with traffic growing faster than the global economy (5-6% pa). Rolls Royce is the UK's largest export business with revenues of £11bn p.a., >75% of which is civil and exported, and over 40,000 employees, most of whom are in the UK.
Co superalloys promise a >100 C improvement in usable temperature capability. In the jet engine business, 0.5% engine fuel efficiency is worth around US$10m/yr in cost and CO2 to the airline per plane, and is the difference between success and failure for an engine programme, being proportional to approx. 10 C in turbine entry temperature. Clearly, success in this programme would provide a sustained source of competitive advantage to Rolls Royce if successfully taken through the subsequent >£1m alloy qualification programme.
People - skills and people pipeline
UK metallurgy and STEM more generally continues to find recruitment problematic. Therefore with the rebalancing of UK attitudes away from financial services and towards manufacturing, it is currently timely to use research outcomes to evangelise society and especially teenagers to build the people pipeline.
However, the reach that individual research projects can have is necessarily limited. Therefore we engage with other projects that target teenagers to deliver this impact, such as the Naked Scientists and Exscitec.
The PDRAs employed will also provide people trained in mechanisms-based, linked alloy and fundamental science development, together with linked computational modelling for insight. With much excitement around ICME approaches and initiatives such as the US Materials Genome Initiative, people with this outlook will be in significant demand.
Organisations
Publications
Azeem M
(2017)
Revealing dendritic pattern formation in Ni, Fe and Co alloys using synchrotron tomography
in Acta Materialia
Chapman T
(2015)
Characterisation of short fatigue cracks in titanium alloy IMI 834 using X-ray microtomography
in Acta Materialia
Coakley J
(2017)
Isothermal omega kinetics in beta-titanium alloys
in Philosophical Magazine Letters
Coakley J
(2017)
Lattice strain evolution and load partitioning during creep of a Ni-based superalloy single crystal with rafted ?' microstructure
in Acta Materialia
Coakley J
(2020)
Femtosecond quantification of void evolution during rapid material failure.
in Science advances
Coakley J
(2016)
Effect of precipitation on mechanical properties in the ß-Ti alloy Ti-24Nb-4Zr-8Sn
in Materials Science and Engineering: A
Ismail F
(2017)
Alloying effects on oxidation mechanisms in polycrystalline Co-Ni base superalloys
in Corrosion Science
Knop M
(2014)
A New Polycrystalline Co-Ni Superalloy
in JOM
Martin T
(2016)
Insights into microstructural interfaces in aerospace alloys characterised by atom probe tomography
in Materials Science and Technology
Vorontsov V
(2016)
Coarsening behaviour and interfacial structure of ?' precipitates in Co-Al-W based superalloys
in Acta Materialia
Weekes H
(2015)
In situ micropillar deformation of hydrides in Zircaloy-4
in Acta Materialia
Yan H
(2014)
Alloying effects in polycrystalline ?' strengthened Co-Al-W base alloys
in Intermetallics
Yan H
(2014)
Effect of alloying on the oxidation behaviour of Co-Al-W superalloys
in Corrosion Science
Yan H
(2014)
Alloying and the micromechanics of Co-Al-W-X quaternary alloys
in Materials Science and Engineering: A
Description | We developed oxidation resistance in this family of Co-Al-W alloys for the first time, and reasonable (<8.5) density, which are key enablers for their practical application in jet engines. This required us to also understand and balance the phase stability to retain and develop an fcc gamma matrix with L12 strengthening nanoscale precipitates. We also have done much work on their manufacturability for a powder metallurgy processing route. The dislocation and creep behaviours, and the matrix strength, are critical to taking this work to the next stage. |
Exploitation Route | This work has been citied by C Sudbrak (NASA) and A Suzuki (GE) as being the most credible work in developing real alloys in this fast-growing field (>50 participants in a yearly symposium). It is being rapidly followed up by fast-followers at Erlangen (Neumaier), IISc Bangalore, GE, and so on - who are citing our papers from this grant. |
Sectors | Aerospace Defence and Marine Energy |
Description | This project is continued in the Rolls-Royce strategic partnership (EP/M005607/1). Two patents have been filed on alloys developed out of this project, that are currently being developed and evaluated for future jet engines. |
First Year Of Impact | 2015 |
Sector | Aerospace, Defence and Marine,Energy |
Impact Types | Economic |
Description | SPII |
Amount | £7,939,564 (GBP) |
Funding ID | EP/M005607/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 09/2014 |
End | 09/2019 |
Description | Cambridge University |
Organisation | University of Cambridge |
Department | Department of Materials Science & Metallurgy |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | We have made test alloys and helped with their deformation processing |
Collaborator Contribution | Drs Howard Stone, Cathie Rae and Nick Jones have facilitated making test alloys with us. |
Impact | Joint publications (see publication list), joint grants (see EPSRC grants on the web), joint patents (see IP) |
Start Year | 2010 |
Description | Rolls-Royce plc |
Organisation | Rolls Royce Group Plc |
Country | United Kingdom |
Sector | Private |
PI Contribution | . |
Collaborator Contribution | . |
Impact | . |
Description | Swansea |
Organisation | Swansea University |
Department | College of Engineering |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | We provided samples for Swansea to test, contributing to their PhDs on this topic, and evaluated the samples post-testing |
Collaborator Contribution | Swansea performed creep and fatigue tests on our sampled |
Impact | Joint publications; contribution to alloy development activities that have resulted in patents |
Start Year | 2014 |
Title | Alloy |
Description | A cobalt-nickel alloy composition comprising by weight: about 29 to 37 percent cobalt; about 29 to 37 percent nickel; about 10 to 16 percent chromium; about 4 to 6 percent aluminium; at least one of Nb, Ti and Ta; at least one of W, Ta and Nb; the cobalt and nickel being present in a ratio between about 0.9 and 1.1. |
IP Reference | EP2821519 |
Protection | Patent application published |
Year Protection Granted | 2015 |
Licensed | Yes |
Impact | This patent is the first in a family protecting future Co-base superalloys for application as turbine discs in jet engines; a critical part of Rolls-Royce's future jet engine development strategy |
Title | Co alloy 1.3:1 |
Description | A Co-Ni superalloy for jet engine turbine discs |
IP Reference | Invention submission 12070 to GB patent office (12 Dec 2014) |
Protection | Patent application published |
Year Protection Granted | 2016 |
Licensed | Yes |
Impact | This is the second in a family of patents that protect a group of Co superalloys for future jet engine turbine discs, a key part of Rolls-Royce's product development strategy. |