An ancient form of metalworking is being used by Rolls-Royce to create a single-crystal turbine blade for jet engines
Casting is one of the oldest and most basic methods of metalworking. If you can make a fire hot enough to melt a metal, and manufacture a crucible to melt it in and a mould that can withstand the heat, you can cast complex metal forms; and we’ve been doing it for millennia. The oldest-known casting is a copper frog made 6,000 years ago in Mesopotamia. Many of the gleaming marble sculptures of Ancient Greece are in fact more recent Roman copies of originals that had been cast in bronze: the few surviving originals, such as the Riace Bronzes of Greek warriors found in the sea off Sicily, show the incredible sophistication and level of detail achieved by these long-dead masters of metals.
Yet this most ancient of skills is still in use today, and indeed is still being developed. Its most recent incarnation is arguably the most advanced procedure that has ever been undertaken in metals, and is vital for one of the emblematic activities of the modern world: routine air travel. It is to be found in the UK’s historic centre of metalworking, Sheffield, at the Rolls-Royce Advanced Blade Casting Facility (ABCF), a facility purpose built near Sheffield University’s Advanced Manufacturing Research Centre in Rotherham.
The components the ABCF is producing are not ones that most people ever see: they are the turbine blades that are hidden away in the hottest part of jet engines. Far from the decorative brilliance of Greek bronzes, they combine a utilitarian appearance with complexity of form and function and a jewel-like internal perfection: weighing only about 300g and small enough to fit in the palm of a hand, they are in fact perfect single crystals of a metal alloy whose composition has been fine-tuned over many years to operate in the hellish conditions of the fastest-moving part of a jet engine.
“Back at the birth of the jet engine, Sir Frank Whittle’s prototypes were made entirely of steel,” said Rolls-Royce chief of materials Neil Glover. “Steel is great for strength and surface hardness, but if you need high-temperature performance it isn’t actually very good; 450–500°C is about its limit.”
Its unsuitability led to a search for a more temperature-resistant material, and jet makers turned to nickel alloys. Relatively abundant, with large deposits in Australia, and low in price, nickel melts at 1,728K (1,455°C) and is resistant to corrosion – both valuable properties for components that function inside a jet engine. Even more important is its ability to form alloys, and the particular property of one of those alloys, a compound known as gamma-prime in which nickel combines with aluminium, to retain its strength at high temperatures. “In steel or even titanium, the strength rapidly drops off as you reach 40–50 per cent of the melting point,” Glover said. “Nickel alloys retain their strength up to 85 per cent of the melting point.
And engine manufacturers make full use of this property. Jet engines work by positioning turbine blades, which spin in the current of hot gases expanding out of the combustion chamber, on the same shaft as the compressor blades that force air into the engine at high pressure. So at the back of the engine, the low-pressure turbine blades, which operate in a gas stream that has cooled down somewhat, are on the same shaft as the large fan blades at the front of the engine, which accelerate air to generate the engine’s thrust. This shaft runs through the middle of the shorter, wider intermediate pressure (IP) shaft, which again has turbine blades at the back and compressor blades at the front. Outside this is the high-pressure shaft, which runs the compressor that forces air into the combustion chamber itself. The combustion chamber is annular, with an exit ring at the back controlling the flow of exhaust gases, and it’s here where the single-crystal blades are found. The gases, fresh from combustion, are at around 1,700°C; and the shaft spins at speeds in excess of 12,000rpm.
This means the blades operate in an environment several hundreds of degrees hotter than the melting point of the nickel alloy. To stop them melting, the metal must be cooled. This is done via two mechanisms: the blades are coated with a low-conductivity ceramic; and they are riddled with a complex, branching structure of internal channels. “Air is drawn from the HP compressor, routed through the core of the engine and into the root of the blades,” explained Glover.
“It passes through the cooling channels and exits through a myriad of holes in the surface of the blade, to create an envelope of cool air around the blade. So the metal is never above its melting point, even though the environment is. The cooling air isn’t actually that cool; it’s at about 600–650°C, but we have to take it from the hot core of the engine so it has enough pressure to get through the channels and out of the holes. It’s still enough to keep the blade temperature down to about 1,150°C.”
Heat is vital to jets; the hotter they can operate, the more energy they can extract from their fuel. This is the major point of competition between engine makers, so over the six decades jets have been in operation, forcing the temperature higher, and developing turbine blades that can withstand the heat, has been one of the most important technology races in the sector. It’s been a gradual process, Glover said, culminating in the development of single-crystal blades in the late 1980s.
“The blades operate in an environment several hundreds of degrees hotter than the melting point of the nickel alloy, but because of the cooling mechanisms, the metal is never above its melting point, even though the environment is.”
Neil Glover, chief of materials, Rolls-Royce
The single-crystal structure isn’t intended to cope with temperature, however; it’s to make the blades resistant to the huge mechanical loads that result from their rotational speed. “Every single blade extracts power from the gas stream equivalent to a Formula One car engine,” Glover said. “And the centrifugal force on them is equivalent to the weight of a double-decker bus.”
Normally, metals are composed of many crystals – ordered structures of atoms arranged in a regular lattice, which form naturally as the metal cools from a molten state. These crystals are typically of the order of tens of microns in size, positioned in many orientations. At high temperatures and under strain, the crystals can slide against each other, and impurities can diffuse along the boundaries between the grains. This is known as creep, and it badly affected early turbine blades, which were forged from steel and later nickel bars.
The first stage in development was to get rid of any grain boundaries at right angles to the centrifugal loading, which led to the development of blades that were cast so the metal crystals all ran from top to bottom. Later, this was optimised further by casting single crystals, with no grain boundaries at all. It’s a highly complex process: not only must the blades be cast with the internal cooling channels already in place, but the crystals are not homogeneous. Rather, zones of different composition and crystallographic structure exist within the blade.
“You can think of nickel superalloys like these as being like composites,” said Rolls-Royce aerofoil turbine materials technologist Neil D’Souza. “It’s a mixture of two phases, one of which – gamma-prime – gives rise to the sustained increase in strength at high temperature.”
When it crystallises, nickel forms a structure known as face-centred cubic (fcc); each cube has a face with five atoms, one at each corner and one in the middle. When alloys are made, generally the atoms just swap in and out of the fcc lattice. But under the right conditions, aluminium and nickel combine in such a way that nickel goes to the centre of the faces and aluminium to the corners. This is known as a precipitate; it forms islands of greater order within the bulk of the alloy, about half a micron in dimension, packed closely together in a rectilinear formation. Because the size of the lattices of the precipitate and the less ordered bulk alloy are almost identical, they are all part of the same crystal.
“You could imagine building a ball and stick lattice model,” said Glover. “In the bulk alloy, you’d place the balls representing the components of the alloy, about 10 different elements including nickel, aluminium, chromium, tantalum and titanium, pretty randomly, and when you got to the gamma-prime precipitate you’d put in this ordered arrangement of aluminium at the corners and nickel in the middle. It’s all on the same regular lattice, oriented the same way, so it’s all the same crystal, but you have these much stronger regions where there’s the array of gamma-prime precipitate.”
But this doesn’t just happen naturally. To make the blades, the first stage is a ceramic ‘core’, of the form of the tortuous internal cooling channels. Wax is injected around this to form the shape of the aerodynamic blade, plus several other features that assist in the casting process. Platinum pins are inserted to support the core inside the wax; then the form is ‘shelled’ by coating it in an slurry of alumina-silicate material to form a ceramic coat. Several more coats of different compositions are applied and then the wax is melted out to leave a void in the shape of the blade. This is investment or ‘lost-wax’ casting, the same technique those Ancient Greek sculptors used to make the Riace Bronzes.
“Our people are fantastically skilled, but they’re human, and no human is going to produce the same quality of work at the end of a shift as they do at the beginning.”
Steve Pykett, Manufacuring manager, Rolls-Royce Advanced Blade Casting Facility
Molten metal is then poured into the mould, which is placed inside a furnace to keep the metal molten. At the base of the mould is one of the additional casting features: a helical structure about the same shape as three turns of a standard corkscrew. Known as the pigtail, this is attached to a plate that is cooled by water. Once filled, the mould is slowly withdrawn from the furnace into a cooler chamber. The metal starts to solidify at the chilled plate, and crystals begin to grow into the pigtail. The crystals grow in a straight line in the direction that the mould is being withdrawn, but because of the pigtail’s twisted shape, all but the fastest-growing crystals are eliminated. Only a crystal with the correct orientation emerges into the blade mould proper, and the gradual withdrawal of the mould ensures the crystal continues growing through the melt into the rest of the space.
The formation of the vital precipitates results from careful control of the external temperature and from the design of the mould; those multiple layers of ceramic determine how fast the heat from the molten metal can dissipate, and this provides the extra finesse to achieve the required internal structure. The platinum pins holding the core in place diffuse into the alloy without affecting its properties.
Once solidified, the casting is removed from the mould and the first of some 20 processes begins to prepare it for assembly into an engine. First, the ceramic cores are dissolved away with caustic alkalis. Then the extra features for casting are machined away. The holes for the cooling air to escape are drilled using electrical discharge machining, which forms the required hole geometry to direct the air to the points where it is needed. Finally, the blade receives its insulating ceramic coating by electron-beam plasma deposition.
The ABCF in Rotherham concentrates on components for large civil airliner engines because, with the advent of aircraft such as the Airbus A350 XWB, for which Rolls-Royce has developed the Trent XWB engine, this is where the company sees its main growth coming from.
Costing some £110m, the ABCF was built to automate as much of the production process as possible. “Single-crystal casting is expensive, and many parts of the process have traditionally been very hands-on,” said ABCF manufacturing manager Steve Pykett. “Our people are fantastically skilled, but they’re human, and no human is going to produce the same quality of work at the end of a shift as they do at the beginning.”
The production of the wax assembly is a good example of this philosophy. “You’ll always find a wax room at an investment casting foundry,” Pykett said. “It requires hand-eye co-ordination and dexterity to make the wax form, but that doesn’t deliver consistency.”
Working with the Manufacturing Technology Centre near Coventry, Rolls-Royce developed an automated system to hold the ceramic core, inject wax, pin the core in place and conduct the assembly process. “It used to take a whole shift to make an assembly; now it takes an hour,” Pykett said. “But time was not the main driver here. We now know that we have consistent product coming out of the wax process, whatever the time of day, and that gives us a solid platform from which we can reduce cost.”
“We’ve transferred some of the skills in making these components from the manufacturing engineers on the line to the process developers. And that doesn’t mean we’ve deskilled”
Mark Hulands, casting manufacturing executive
Some other processes have also been automated, including the dressing operation to remove the sacrificial features of the casting. The blades then go into inspection, where Rolls-Royce has replaced five processes with two. The castings are then shipped to another plant at Crosspointe, Virginia, for further machining of the features that will allow them to be attached to their discs in the engine, and for drilling of the cooling holes; they come back to a plant in Annesley, Nottinghamshire, for coating.
“This process is so complex, with precise control of temperatures and materials handling to manage, virtually atom by atom, how the blades are formed,” said casting manufacturing executive Mark Hulands. “What we’ve done is to transfer some of the skills in making these components from the manufacturing engineers on the line to the process developers,” Hulands said. “And that doesn’t mean we’ve de-skilled. Our engineers still need to be highly skilled to keep the processes running smoothly, but they’re different skills and we’ve improved the consistency so we can drive costs down.”
Read about Rolls-Royce’s record-breaking UltraFan aerospace power gearbox
I read this article with increasing joy and pleasure at the skills defined and described. [In the summer vacation of 1962 I was involved (on the very periphery!) at the Bristol Siddeley facility: working (I am sure rather poorly) at assisting the proper Engineers and operatives with a small enhancement to the ‘lost-wax’ process: used to construct the blades on the original Olympus engines for Concorde.
These were in titanium, with glass rods (with a bend in them) suitably positioned within each ‘pour’ to become the cooling channels in the blades: after the glass had been etched ‘out’ by a very viscous acid (I want to say Hydroflurous) but that may be incorrect. I do recall that the scrap rate was well into double figures!
In 50+ years the technology has advanced by several orders of magnitude as frankly it has in almost every area of science, medicine, even (I will allow you!) the arts.
Which other areas of our lives, the administration of the State, the settlement of disputes, the election of our leaders, the management of staff at all levels, the counting-up and manipulation of the numbers that define firms, organisations, even the state itself….the comfort of religion, the beauty of creation….can claim a similar advance. Will someone please tell me? From what I can see, they have gone backwards about as many ‘steps’ as we have gone forward. Perhaps it is indeed time for ‘us’ to have a go on the top table!
So did I.
I can answer your question, I think, at least to a first decimal place. These incredible engineering achievements were made by people who wanted to solve a problem. They were optimising for engineering efficiency. Nowadays, people are optimising for their careers, not problems that need to be solved. I think it’s a sign of rot in a company as soon as they start hiring people for whom their careers are more important than the problems to be solved. Unfortunately, there are a lot of rotten companies.
I am happy to read about Single crystal technology .It is possible to get current update/Innovation in Aircraft Engine ? I am student of Aeronautical Engineering and like to touch with current innovation happening in Organization.
*Hydrofluoric acid – has a very strong odor. Sounds very impressive – RR are a real British success story. If only we had a car industry of the same quality.
The Internet!
Well with new blockchain technology many of these problems or non-advancements will be fixed as trust will be redefined. But it certainly took a long time to advance
Wonderful comment – thank you!
Always comforting to hear technology truly appreciated as the greatest of all human art forms that it truly is; as ‘real poetry’ in other words.
Nevertheless, I think it would take a book, or several – and by people far clever than me! – to answer your concluding queries. So excuse me if I restrict my response to a single observation, and that is this:
I think at least part of the reason why some of these ‘other areas of our lives’ don’t function quite as ‘smoothly’ as the deeply IN-clusive COLLABORATIVE one described here is surely because they are inherently EX-clusive COMPETITIVE ones.
The article mentions this underlying/overflying, Darwinian fact of ‘life in the fast lane’ (make that jet plane) more than once, and it is also recognised in the collaboration between this blade manufacturing facility and the ‘ivory tower’ over the road – where people like myself (and possibly you?) often feel more at home – ‘left alone’ to ‘do our thing’ – and no doubt frequently being very creative in the process.
That said, my own experience of the manufacturing process suggests that this can be at least as creative as the initial design one, frequently more so – but nevertheless, still best conducted in an atmosphere of open-minded, open-hearted ‘university-style’ collaboration than in a crude ‘them-and-us’ competition (like a bad football match). Rule-bound environments often merely serves to stifle creativity, as the Japanese have been discovering in recent years to their cost. I’m sure you know what I mean. That’s why Apple & Microsoft started calling their facilities ‘campuses’ after all – a generation ago. Stupid? Affected? Maybe, but don’t you wish you had bought a few shares..? As even their very name implies, ‘Anglo-Saxons’ are basically a collaborative bunch – and our language, English is a fundamentally eclectic one. Our natural inclination is not to reject strangeness but to embrace it.
So why can’t we simply transfer this knowledge of the profound satisfactions of creativity collaboration to ‘other areas’ – like religion, politics or (dare I mention it…? No, I’ll just call it:) marriage? Because these doubtless noble institutions are based (like capitalism) on DOGMA and either/or, black or white, two-party ADVERSARY SYSTEMS. They aren’t supposed to be benign and inclusive. ‘All’s fair in love and war’ as the man said. Can you imagine a ‘coalition marriage’? OK, maybe so; but my wife can’t.
And here’s something another man said:
“Insanity in individuals is something rare – but in groups, parties, nations and epochs, it is the rule.”
That’s the human tragedy in a nutshell isn’t it? Apparently, without adversaries like Boeing to spur us on, we mere foot-soldiers are incapable of even getting up in the morning.
PS I’ll leave you to source the quotes and read the books! It’ll take you the rest of your life, and probably most of the next one too. GOOD LUCK KINDRED SPIRIT! Keep an open mind, that’s the big secret.
A great article and an really encouraging advert for anyone who wants to enter engineering. Science and Engineering combined, could you ask for more.
It’s amazing how the metalworking has transformed the world, but there are countries that take this beyond technology.
Metalmecanica en Cali
Fabio might enjoy the slogan of the Foundryman: “the hand that pours the ladle rules the world” though we textile persons say “the hand that rocks the shuttle….” and we all know that it is women who actually run everything:
“the hand that rocks the cradle, rules the world”
Notwithstanding Anon’s view of Anglo-Saxons as basically collaborative …I have opined for the 40 years of my research into its nefarious ways that it is the adversarial process (as opposed to the inquisitorial approach used almost throughout Europe and all Asian countries, except those who had the misfortune to be ‘our’ former colonies… I say black, you must say white or lose face…and the arguement! which is the true curse of the Western Democracies who use it. Far too many livelihoods consequently depend on the conflict, not its outcome [interestingly, the vicars, lawyers and military, those who go to work in fancy dress, have elaborate initiation techniques and are appointed by/hide behind the Royals…] I did actually. have a letter in the Times to that effect. I had a General spluttering in his cornflakes as “disgusted, Tunbridge Wells”, the next day!
Definitely a result.
Mike B
A very interesting article covering the history of aircraft turbine blade development and, in particular, the ‘single crystal blade’.
In a somewhat similar fashion to Mike Blamey, I, almost by chance, followed the development of the jet engine over many years.
I started my engineering draughtsman apprenticeship at BTH, Rugby in September 1955. Almost immediately I was told that Frank Whittle had first developed his jet engine within that factory site. Indeed, one could stand on the high gallery, at the Main Drive end of the Turbine Factory and Assembly Shop (still there today and now part of G.E.Energy, Rugby) and ‘look down the long workshop’ and have pointed out the area in which those first prototypes were actually run/tested. It soon became apparent that such testing, in a normal working environment, was too dangerous. This was emphasised by a turbine shaft ‘breaking free’ (blowing the cap off) possibly during an over speed test, and the shaft ‘shot up vertically’, went out through the roof and landed 400 yards away. A purpose-built overspeed building was then constructed and later replaced by a reinforced concrete, thick walled facility in which (one of) my landlords worked (Len Archer). In what must be one of the worst business decisions ever, BTH, in their ‘wisdom’ must surely have fallen out with Whittle and one can trace his future history elsewhere. In 1967, I found myself working for Nuclear Design and Construction, Whetstone, near Leicester and ……. was amazed to learn that Whittle had also operated from there. He had a series of low sheds, on the periphery, at the rear of the site, now close to the M1. I actually walked over to see them!
Much later, in about 1990, I worked, maybe a year for Devlieg, a machine tool company, who had a design office and factory in old premises in Lutterworth. The factory quite ‘stands out’, situated alongside the M1 and having a VERY tall chimney stack. It turned out to have been, for sometime, Whittle’s factory, having originally been a foundry.
Over the years, I also worked for Rolls Royce at the Moor Lane Engineering Design Offices as an ‘off site’ contractor. I had three stints in all, totalling some 10 years, working with and for some great guys, some of whose names I’d have to look up. First on was a lovely guy, Maurice Wain. In the late 1980’s, I was usually reporting to Roy Wilkinson, then Chief Draughtsman and our Rugby Design Team, as part of a variety of work, were involved in the then new ‘single crystal’ H.P.Blade, producing various detail drawings, from R.R. Design schemes. We did learn that the blades were ‘grown’ but not in the detail described in the article, more in the way of how crystals were grown from chemicals in one’s school laboratories but we better understood the air cooling and the ceramic coatings, the specifications for which we used to quote on the drawings, plus the quite surprising information that, at that time, it was a fairly small company in Leamington that was ‘doing the coatings’. R.R. Was a truly wonderful company with which to be involved and, as a regular, say twice weekly visitor, I felt that my team would both appreciate and benefit from a factory visit. Our R.R. Liaison Engineers fully agreed but security considerations prevented visiting Moor Lane but a group visit was arranged to the R.R.Training Centre, just outside Derby, where engine fitters from all over the World are trained to strip down/rebuild engines. Our last work was in producing many drawings for the then new Trent version, designed, if I correctly recall, for the Lockheed MD11 aircraft. Of course, all those drawings were produced, over those many years of my involvement (1968 – 1992?) in firstly ‘pencil lead on quality tracing paper’. Then using ‘plastic pencil leads on plastic film’ (the film had a shiny smooth back but a very fine abraded drawing surface) and those plastic leads were tricky, brittle and required a ‘plastic rubber’. Drawings were becoming an increasingly valuable item, in the way that they had to be supplied to R.R. accredited workshops all over the World and ‘read’ with no compromise. R.R. made huge efforts to make such drawings ‘fool proof’ with a regular weekly ‘drawing quality group’ meeting, where drawings, randomly selected, were assessed by a multi-skilled team (I was invited to attend on a number of occasions), in order that I, and others, could ‘pass on’ the reasons for both praise and criticism of the quality, readability and elimination of any ambiguity of information, presented on such drawings. R.R. then moved to having drawings produced using ‘Indian Ink’ on plastic film. This resulted in even crisper reproduction, with prescribed line widths and stencils for uniform height of lettering.
Of course, as another contributor mentioned, development and the pursuit of excellence is a continuous feature of R.R. Very soon, the need to super-accurately interface with the Boeing airframes brought in the, initially very limited, use of 2D computer graphics but in no time at all, so it seemed, the pencil and even the fancy ink systems were consigned to history, as was my involvement with R.R.
Fortunately, for me personally, I retrained, at least on to 2D computer graphics and my accumulated engineering knowledge enabled me to ‘be in demand’ until aged 74. Even in my last two projects, there was no escape from the technical ‘superiority’ of R.R. Around 2009, I was producing drawings of the Synchronous Alternator/Generators for the ‘now being fitted out’ new UK Aircraft Carriers. The G.E.Energy (then Converteam) machines were to be driven by an R.R.Trent engine and the whole arrangement was mounted on a skid, all under the overall design and manufacturing control, as I understood, of R.R in Bristol. Then my very last project in 2011/2, a G.E.Energy Vertical Thruster Motor for Oil Exploration Drilling Ships, again had R.R. at the helm, providing the propellor system, which the motor powered, to keep such ships on GPS position (6 units per ship).
Not a bad innings and some fabulous experiences working with very gifted people.
Hi do you know who was responsible for the design of the cooling holes in the blades
It’s wonderful to read about the latest methods of turbine blade manufacture, but somewhat disheartening at the end to realise that many skilled technicians had to lose their jobs to facilitate the advance. Alas, this seems to be the way of manufacturing advances everywhere one looks, a shame, really in a world where ever more people clamor for jobs to provide for basic necessities. Perhaps someday there will be a way to incorporate human processing power back into processes increasingly dominated by machines.
‘Cyborgism’ is the answer to the perceived redundancy of human labour in manufacturing.
Beautiful technology… it’s things like this which just take the breath away.
Thank you for this information.
I am a M.S. student in mechanical manufacturer and automation for doing my final project about some simulation and prediction of fatigue life, I need some more information about turbine disc dimensions. I just want to know the max. and min diameter and number of blades of turbine disc which are used in either jet engines or power plants. I would be very thankful if you help me with this problem.
Not an easy question to answer. I have moved on from aviation now but each engine type is unique for its own function. Obviously military engines require far higher thrust to weight ratios and smaller packaging so would tend to have smaller turbine disc sizes, and therfor also possibly smaller baldes making up each disc. Where-as high by-pass airliner engines can afford to be larger and more fuel economic. Although both share the common goal of extracting maximum energy from the combustion process. Another thought to consider is, as mentioned in the article there are many tubine discs in modern engines with one or more turbine disc connected to each compressor disc set by the central shafts. As you move away from the combustion chambers the turbine discs tend to get larger diameter and longer wider blades to extract the energy from the now slower, cooler combustion gasses. In short there is no one stop answer to the question, even if dealing with a single engine type I’m afraid.
Perhaps contacting Rolls-Royce direct would help obtain some more targeted answers but I would think you would need to get defined questions for objective answers.
Not-withstanding this a good place for general information would be the book ‘The Jet Engine’ by Rolls-Royce / Wiley which formed the staple reference for R.A.F. technicians in training for many years (indeed if it still doesn’t). Its listed on Amazon, but I’d try a good library first ISBN-10: 1119065992 ISBN-13: 978-1119065999 .
As a side note the engines used in power plants are a totally different beast to those in aircraft as power plants (and Helicopters and turbo-prop aircraft for that matter) typically use constant shaft horse power type engines, as opposed to variable thrust engines used in typical aircraft or military jets. Constant shaft horsepower engines are usually considerably smaller than their variable thrust counterparts and have much more benign operating parameters.
“The holes for the cooling air to escape are drilled using electrical discharge machining, which forms the required hole geometry to direct the air to the points where it is needed.”
As i am sure our Editor and other bloggers are aware, much of my career has been in the synthetic fibre (and related) industry. The very heart of our processes -the point where molten polymer as an extremely thick viscous liquid is forced through the spinnetette (a plate containing profiled holes in ‘settings’ and number to match the number of filaments we require for different yarns -spiders use only one, but you get the idea) depends on the accuracy and repeat-ability of the cutting of the orifices: and the way they are cut is via electrical discharge machining (spark erosion?) fascinating to see how different industries use similar techniques to develop the ‘watch-maker precision, 100 metres long’ which is a description of ‘our’ needs. I have a feeling that there is sufficient synergy that Engineers from one sector (engine blade manufacture) may both teach and learn from the other(synthetic fibre) How can we arrange develop this?
A fantastic process but why do the blades have to go to the USA for the fir tree machining – is there no one in the U.K. capable of doing that?
Just to say that it would have been Hydroflouric acid which was used-I used to use it at Cambs. UNI. Pollen Lab for dissolving the minerals but leaving the pollen grains unscathed-amazing stuff, pollen. Needs lots of care, as a drop on the skin will almost certainly kill you
Hydrofluoric acid has a topical antitdote that should be nearby any flume cupboard handling this chemical. It’s nasty stuff and smells very strong almost like ammonia – I did inhale a bit once by mistake – I didn’t feel ill at all.
Did you consider reinforcing the blades with basalt fibre?
Might have missed it but why no acknowledgement that directionally solidified and single crystal nickel alloy gas turbine blade technology was invented and developed to bill of material status under the guidance of Frank Versnyder at Pratt & Whitney’s Advanced Materials R & D Laboratory in Connecticut in the 1960s? Nothing to do with Rolls Royce!. At that time they were focused on material improvements by forging!
Not sure when this correspondence commenced (after Stuart’s article?) but somehow the dates of comments seem somewhat jumbled. Thank you sincerely, to any who commented so graciously on my original comment. And thank you to those who added their obvious outstanding technological, managerial and historical knowledge to hopefully develop all our thoughts on these remarkable elements of the ascent of man? I hope that any students joining the debate, if nothing else recognise that Engineering like so much of technical and commercial life “depends on shared information!” Sharing without reservation, and that both ‘inside’ and between entities of all types. The Laws (those of Nature) we seek to direct towards the ascent of mankind are identical the world over: and indeed breaking any will result in immediate detection and punishment. Other so-called professions are less fortunate: and so are their clients!
Fascinated to read the article and subsequent comments. Athough i began my career researching single-crystals of metals and refractories, much of my later research was on single-crystals for optoelectronics and piezoelectrics. Now in retirement I give occasional lectures on the diverse application of single crystals -from sugar, salt and snowflakes to single crystal turbines -or, at least , turbines would be the end of the spectrum, if I could find a reproducible copyright free photo . Can anyone oblige?
A well-written and clear article on the power of Materials Science and Technology and its effect on daily life, i.e. cheap foreign holidays. Similar materials applications are in carbon composites, which at one time were only good for golf clubs and tennis racquets; now we have whole aircraft built of them.
Considering that initially LED’s were a novelty, now through development of the right materials they have replaced filaments and reduced power consumption by 90%. That’s before we start on carbon nanostructure science.
A pity that few Students have been impressed enough to take up the study and our University Dept. closed. What can we do to encourage our young people to investigate why their touch screens work?
Thank you for this very interesting article – RR at its best!!
With every blade being such a complex and valuable piece of engineering, I wonder whether every blade was actually fitted with a unique identifier (e.g. Barcode, datamatrix code) to capture the full traceability of its history?
Re. etchant to remove glass from titanium: hydrofluoric acid will etch glass but even as a cool and dilute solution is a extremely aggressive corrodent for titanium so I wonder whether they would have been titanium blades. Nickel based alloys, in general, are more resistant to the acid and some compositions eg. HASTELLOY(R) B Alloys and later derivatives are used commercially in the manufacture of chemical plant handling these acid solutions.
Single crystal blade in aero-engine is the first key part of aero-engine, which is located in the parts with the highest temperature, the most complicated stress, and the worst environment, which directly determines the performance of aero-engine. Visit https://www.samaterials.com/ for more information.
Interesting the university department got shut down..
Does RR run their own apprenticeship program?
This is a wonderful article which I have read with keen interest. It’s great to see that ultra advanced engineering and manufacturing is taking place in Rotherham. Congratulation to the brilliant and innovative engineers working at Rolls Royce. Britain should be justly proud of such exciting achievements.
Before I retired, the company I worked for manufactured the “glass” cores (which were actually made from ultra high purity fused quartz >99.99% SiO2) used in the casting of numerous types of blades at Rolls Royce at their Precision Casting Facility in Derby and also their precision foundry in Bristol.
We had a department which was dedicated to producing these cores from high precision rods which we manufactured by drawing from a preform using a drawing tower (originally designed for producing optical fire) in various profiles including round, racetrack and aerofoil. The rods then had to be cut to length, bent, and machined to form the required shape.
A single turbine blade required a set of cores (typically seven) all of which were different.
As blades became more complex the cores also became much more complicated and could no longer be manufactured using our process so we only continued to supply cores which were used to produce spare blades for existing engines.
My company was then taken over and the new owners had no interest in the core business (and a number of other processes we had) and the core manufacturing department was closed (but not before we manufactured a large quantity of cores for our customers stack to allow blades for spare parts be cast).
Incidentally the cores were removed from the casting using a caustic alkali (not acid) in an autoclave as this causes the fused quartz to devitrify and break up. (This is the same reason why you should not touch a quartz halogen light bulb with you bare hands as your skin oils are alkali and cause the areas that you touch to devitrify. This results in the fused quartz changing state in to cristobalite which has a much larger coefficient of expansion that the fused quartz (whose coefficient of expansion is virtually zero) and causing failure because of differential expansion.)