Diamond Like Carbon

[Neil WyattModerator @neilwyatt]

[Neil WyattModerator @neilwyatt]

Has anyone come across this:

en.wikipedia.org/wiki/Diamond-like_carbon

I just read about a bicycle chain coated with it.

Neil

[Ex contributorParticipant @mgnbuk]

We have some milling cutters at work with a DLC coating. Trying it to see if it improves tool like machining graphite & carbon composites, both of which are abrasive. I havn't heard much about how successful this has been, though there hasn't been much through the works of late that would have called for this tooling.

Also seen that it is used on some high-end motorcycle fork tubes in place of a titanium nitride coating for wear resistance & reduced friction.

There seem to be a number of companies in the UK that can do this – doubt it would be cheap, though.

Nigel B.

[Oily RagParticipant @oilyrag]

I know it as DLH (Diamond Like Hardness) and have worked with it since the late 80's. Originally used in engine component coatings to reduce friction and wear, its use was initially by Renault F1 engine engineering as a spin off from the aerospace industry.

Commonly applied to high load/stress parts such as cam lobes and cam followers – since the advent of pneumatic valve control systems in F1, engines were able to rev to far higher speeds due to the inertia and resonance of wire springs previously being a constraint. The 'air valve springs' also meant cam lifts were now only constrained by piston 'clashing', this resulted in lifts of typically 28mm, with reduced cam period of around 260 / 270 degrees from previous 'wire spring' era of 320 degree plus. The acceleration rates now were astronomical but the DLH allowed this with the higher load bearing capabilities. One supplier we used was Oerlikon the famous gun manufacturer and supplier to the aerospace and armaments industry.

Next you'll be hearing about the gold plated engine internals – done to allow the use of titanium exhaust and aluminium inlet valves! And gold plated piston crowns!

[egaParticipant @ega]

Who needs to talk to the engineer when you can get such interesting information from one or other oily rag?

[Oily RagParticipant @oilyrag]

Indeed! I initially thought I had already posted a comment – then saw there is another Oily Rag on the forum, me, I'm just the common or garden oily rag whereas the other is the definitive one.

For anyone interested in F1 engines the early 90's Megatron Renault engine was designed and built by Danielson at their facility in Magny Cours, these were the people who initiated the use of DLH as they also have an aerospace division and worked with Dessault. My involvement was with the Yamaha V10 as used by Tyrell and then Arrows, the Yamaha engine was designed and built by John Judd at Rugby. Arrows Engines then took over Brian Hart's facility and developed his HV10 engine.

The Judd 'Yamaha' V10 was a jewel of an engine weighing in at just 92kg and very compact despite having 92mm bores, being just 650mm long. It was powerful but a little fragile though. The Arrows Hart engine was a heavy lump and underpowered but was developed into the eventual Championship winning Renault engine of the Red Bull team in the early 2000's.

One development 'dead end' was the use of carbon fibre intake trumpets and runners to the back of the valves. The engine refused to rev over 14,000, going into an insipient misfire. Everyone assumed this was an ignition related problem, but despite 'turning up the wick' on the ignition energy the misfire would not go away. I got the technicians to run an 'end of life' engine up to the misfire point and to hold it as long as they dared then to cut it dead whilst I dashed into the test bed and peered down the trumpets – sure enough in a 25c ambient we had ice formation in the inlet tracts due to the lack of heat for vapourisation of the fuel. We later calculated that pre combustion (i.e in the inlet tracts) required 3kW of heat input to vapourise the fuel prior to the 'in cylinder' vapourisation (i.e the 'vapour gas exchange' process) at just over 3 millisecs time interval this was asking a lot at 20,000 rpm. The gold plating process to the piston crown, valve faces and combustion chambers had the advantage of retaining heat in the cylinder to the extent that valve head temperatures dropped by an average of 80c, piston crown temperature was also significantly reduced. This was because the infra red heat was reflected back into the cylinder – another advantage of the gold was that, being inert, carbon would not 'stick' to the components and they came out at 'end of life' like new components! My time in F1 was the best days of my career, hard work, long hours, lots of travel, life in hotel rooms and little time for any hobbies – except when I managed to race my classic bike!

[Clive FosterParticipant @clivefoster55965]

As a sometime professional in the thermal imaging, target detection, target stealthing et al world my initial involvement with DLC coatings was in research projects to improve the life of IR and multispectral transmission windows in harsh environments around mid 1980s to mid 1990s. Especially mutispectral ones which tend to be rather soft and suffer badly from rain impacts in aircraft use. Normal IR windows and lenses covering the 8 to 14 micron bands were not so much of a problem as the materials are closer to glass in hardness. But even glass could use a helping hand.

Expensive back then. Dropping one of the big 12 inch (or more) germanium front elements for IR telescopes on TICM and the like would not have been a good idea. Maybe pushing £20,000 a pop for one experimental element after coating. Worth it I guess to nudge the optical diffraction limits and physical transmission limits and get the absolute best out of a tuned up TICM 2.

On the mechanical side I got Oerlikon-Balzers to coat the innards of my Norton Commander gearbox hoping to finally cure the endemic hardening spall failure of the third and fourth gear pairs. Stretching the old Triumph four speed cluster designed for maybe 30-35 soft tuned twin hp to take 90 odd aggressive rotary ones was maybe a touch optimistic. Especially after lengthening the mainshaft to make room for a fifth gear. Predictably the thing bends under load, the ruler straight power curve and relentless torque of the rotary probably don't help, which is less than good for gears. Norton factory issue SAE 140 gear oil was never going to cut it over significantly more than 50,000 miles. My first try was Castrol R which seemed good for at least 100,000 miles. Coating + R should be a cure. At £800 odd I certainly hope so. I may not live long enough to find out!

The idea of gold plating pistons to reflect IR sounds a touch off to me. When it comes to reflecting IR smooth and shiny is fine but at combustion temperatures there is a good deal of visible in the mix which needs a polish. I'd expect the gain to be more from carbon not sticking helping keep the surface smooth. Of course carbon black, which effectively is what is deposited inside an engine, comes about as close as any easily gotten material can be to a perfect black body over combustion emission wavebands. It absorbs nearly everything that hits it, warms up and re-radiates. I'm surprised you only lost 80°C off valve head temperatures and, I guess, 40°C off the piston crown. I saw claims that at least double that should be possible with appropriate coatings. And got to check the maths.

But the field was always rife with over-optimistic speculation and misinterpretation. I'd like a quid for every time I had to explain that you can't reflect cold. If you want to be malicious you can do a really pretty lab demo tho'.

Clive

Edited By Clive Foster on 15/10/2020 13:30:21

Edited By Clive Foster on 15/10/2020 13:30:42

[Oily RagParticipant @oilyrag]

Clive, interesting input!

In an engine the temperatures fluctuate with the cycle, RR56 piston material is limited to ~320C, by 350C it has lost over half its strength. But a piston heats and cools through the engine cycle going from around 400C at the end of the exhaust stroke to around 130C at the end of the induction stroke, measured in the crown centre (other areas are less then this as you move away from the heat concentration point); this is in less than 3.3 millisecs at speeds above 18,000 rpm. The key was to keep the piston below an average of 320, but better at less than 300C. Again valve head temperatures quoted are averaged through the engine cycle – so an 80c reduction in average temperature. These valves were titanium exhaust and aluminium alloy inlets. Many people have tried to thermally coat piston crowns, the biggest problem is the usual silicon carbide based coatings flake off due to inter granular separation at the host material/coating face due to differential expansion rates between the two compounds. Gold was a very effective coating as the piston base material was prepared with an 'affinity' element which gave a molecular level bonding.

Aluminium/Berylium alloys helped (interestingly first used in the Moto Morini 250 single race bike of the mid 60's) but were then banned by the FIA in the middle to late 90's. We then moved to a Aluminium/Lithium alloy which was good but not on a par with AlBeMet alloys. The gold plating gave around a 50C average reduction in temperature in the piston crown.

Did you ever work on the direct engine combustion feedback system being developed in the 90's? This was a quartz multifaceted 'window' into the combustion chamber that via fibre optics fed a SIS (super imaging system) to then analyse the combustion in real time via filtered wave length. the spectrum was then plotted against crankshaft position to give an effective combustion monitoring called Real Time Digital Analysis. The idea was aimed at doing away with the lambda sensor monitoring exhaust gas oxygen content and to give optimised ignition and fuelling. It was a very effective system in prototype form. One of the problems was keeping the carbon off the quartz 'window' – a gold flash was quite successful but difficult to attain the correct thickness coating.

As for the Norton Commando gearbox the answer to tooth spalling is to make the gears in a Maraging steel rather than the production EN32 or EN36. 'R' certainly helps the gears as its has a far superior temperature breakdown to mineral oils, although some of the synthetics now are as good if not better – try Castrol 'XC27' if you can get hold of any (but it costs a small fortune!) Its what I run my BSA racer on – including the gearbox. The BSA gearbox has a small gear pump to feed the oil to a spray bar which keeps the gears well lubricated and removes the heat. The g/b oil pump feds via a small external oil cooler (a Jaguar V12 fuel cooler used in the US model XJR-S's). These measures will help prevent the gear tooth erosion (spalling) when you put 50+ BHP through a C15 type gearbox!

[Oily RagParticipant @oilyrag]

Ian B – I was in no way intending to be either deprecating or offensive towards you (assuming you were the one using the name 'The Oily Rag ), if it came over that way I apologise to you profusely. I have no problem with you continuing using the 'handle'.

[Howard LewisParticipant @howardlewis46836]

Fascinating to read the really high tech matters in which contributors have been involved

Makes the Schieren photography of cylinder events used by our Research boys sound a bit old hat!

keep up the saga!

Howard

[Neil WyattModerator @neilwyatt]

This is not where I expected this debate to go!

Now I have identified both Oily folk I can say: What a sticky situation?

Oily Rag got his name in January 2010.

Ian B. (or The Poster Formerly Known As The Oily Rag) got his name in October 2009.

It would seem that the pair of you have been sowing confusion for almost a decade without this clash of might wills happening before!

Strictly, in terms of priority, if there needs to be a change, Ian B. had the oleaginous title first, by nearly three months.

May I ask the two Oily Raggers to communicate with each other by PM and come to a civilised agreement. I would suggest that 'time sharing' the title is probably not ta practical situation.

May I also thank all posters for their information on this intriguing surface treatment.

Neil

[Paul LParticipant @paull58212]

DLC is now used (for about 15 years or so)  in F1 engines since the life of each unit has to last more than one race. Camshafts are machined out of a solid billet of tool steel,Gun drilled to give a bearing wall thickness around 2mm heat treated (nitrided?) and then given a DLC coating. Certainly a step up in price and performance from the old cast iron jobs!

I've also seen the pistons with DLC coating on the skirts.

Paul

Edited By Paul L on 17/10/2020 09:50:21

[David George 1Participant @davidgeorge1]

A friend of mine does the coating mostly for Severn Trent to put a wear resistant coating on pump shafts where the seals make contact.

David

[John MCParticipant @johnmc39344]

Ian B.'s comments on depositing gold on to things to examine in an electron microscope brings back memories of 10 or so happy years working in a metallurgy laboratory. Always done on non conducting specimens, a fly was always a good example to show visitors before getting down to the serious stuff!

There is a motorcycle chain new to the market that claims not to need lubrication on its sprocket interface surfaces. Also very much increased life. I wonder if that has a coating as described in this thread?

John

[Clive FosterParticipant @clivefoster55965]

That direct engine combustion feedback through a quartz window system sounds really interesting. But I'd lay odds on it being something that initially worked well at the demo level before deviating into a quagmire of complexity to make it work properly all, rather than most of the time.

My field was more on the low temperature end of things involving target detection and identification. The combustion aspects, with suitably loud sound effects, were handled by other folks.

New gears for my Commander gearbox were never going to be economically viable. I did ask Quaife after Norton had shut down but the minimum order quantity and cost were way out of my pocket. I doubt if there are more than 500 rotaries out there and most of those will never cover enough miles to kill the gearboxes. Nortons answer was going to be F1 type motor with Yamaha gear cluster. Plenty strong enough but my Norton box with coated innards has a much nicer change that the Yamaha box on my GTS which is the same cluster as the F1. Norton clutch is far nicer too than the Yamaha version which is very light switch in action.

Given the marginal lubrication under racing conditions I'm surprised that Nortons didn't use DLC on the rotary engine main shafts, rollers et al to increase the time between replacement.

50 hp through a C15 type gearbox is impressive.

I learned the Castro R trick via a friend from a man trying to keep a seriously tuned Vincent sprinter from destroying Burman gearboxes. In a gearbox the best thing about R its ability to carry high loads whilst maintaining a relatively thick oil film. So it tends not to squeeze out sideways so easily if a shaft deflects.

Agree wth Ian B that the late 70's, 80's, and 90's were a good time in R&D. A lot of the basis for modern electro optics and engineering refinements surfaced in that era and were polished into usefulness. As, probably, one of the first people to actually demonstrate "imaging" use of a CDD detector I found the speed with which it went from "total crap but if we are creative.." to "more than useful pictures" status quite amazing.

Clive

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