slo

iTrader: (1)

Has anyone thought about, research or can comment on DLC coating of new housings?

Not thinking of a way to refurbush old housings, just want to make new housings last longer.

A coworker of mine has an affiliation with motorcycle racing team told me about new lined aluminum cylinder's getting a super thin coating of DLC over there existing lining (not sure what the existing lining is) and then basically lasting for hours of race track usage at 10-15k rpm with no wear and being up a few HP because of less friction on the sliding surface.

He was saying that the coating is so thin that it shouldn't reduce the clearance below the spec, apparently so thin as to be barley measurable with normal equipment

They apparently calculated that the coated parts would last for over 50 years worth of racing.

Any educated opinions?

Kyrasis6

DLC coatings are only like .000003" thick. If I remember right they will not hold up to combustion temperatures, but yes when done right they will make a part almost impervious to wear. There is a catch though, the surface needs to be polished to like a .5 ra or less otherwise it is like diamond coating a hack saw blade and instead of reducing wear it will cut anything that rubbs against it all to ribbons. Expect to pay more than what you would pay for new irons to have have it done "properly".

slo

iTrader: (1)

Well the surface they would be coating would be the chrome of a new rotor housing, not an iron (should be smooth enough).

They apparently do stand up to combustion temps I believe they are used to coat the black RA apex seals.

The incredible thinness is the point, they could coat in spec parts without taking them out of spec, and they would take on the " micro pourus" surface texture of the chrome, and should retain oil like stock (testing would have to be conducted).

Imagine all that happens if the coating wears through, your still down to a brand new housing below it.

The point is not to reuse worn parts, but to make new parts last longer. I would pay an extra 200 dollars per housing for housings that never wear out and maintain compression forever, especially in combination with ceramic seals.

TonyD89

iTrader: (10)

Kyrasis, I know you have machine shop experience. So do I. Are DLC's like PCD's (polycrystalline diamond)? We cut a lot of graphite and PCD coated carbide end mills are the ****. They outlast an uncoated one 10 to 1. I think the coating may be thicker. Like .0002". I really don't think I've seen one as thin as the one you stated. It is hard to believe something so thin could make a difference.

Over the original chrome? Why not? I'd check into the process though. Some of those use a lot of heat and/or corrosive chemicals.

2Lucky2tha7

iTrader: (3)

interesting

slo

iTrader: (1)

I don't know for sure, but I think .0002" added on onto new housing might be acceptable, thats still a very thin coating.

After some searching I have read on the Rx8 board Rx8 corner seals are coated with DLC.

RacerXtreme7

iTrader: (2)

A way to make new housings last longer??? BUY CERAMIC SEALS!!!


~Mike...........

slo

iTrader: (1)

I am going to buy ceramic seals

Kyrasis6

From personal experience I would be hesitant to coat rotor housings with DLC. Parts of hard seals, and the seal grooves.... absolutly. I would not coat the housings themselves. Too many times I've seen a vendor slightly screw up, or the microfinish not be perfect, or something in the oil not be right for some reason and the result was complete destruction from the DLC cutting it's way through parts.

You are completly right about the parts still being good when the DLC does wear though, the engines I worked on, some of the parts would be replaced after every race, when we started DLC coating them we would run them 2 races before sending them for recoat, some of these parts had well over 24-30 races on them because we where able to recoat them when needed.

slo

iTrader: (1)

When you say, microfinish, do you mean a process that takes place after the coating is applied (to the coating itself) or the finish of the part prior to the coating?

All of the new mazda housings I have seen have been consistently just about perfect, but then I have never looked at them under a microscope.

So what your saying is if it was done right it would be good, but thats a big if?

Any idea how much it would cost to coat something like an entire rotor housing (the wear surface only of course)?

What parts do you guys coat in these race motors? Cylinders or cylinder liners?

Kyrasis6

The DLC coating is only like 3 microns thick, so it will take on the finish of the substrate it is on. The microfinish needs to be measured by a high end profilometer, the one we used cost about $20k. Brand new housings from mazda are no where close to having the proper RA (microfinish) to take them out of the box and send them out for DLC coating. If the finish isn't a PERFECT mirror image then it is already too rough. If it is a mirror finish you still need to check it with a profilometer to make sure it actually is smooth enough. When we coated our parts even though they looked perfect when we got them we still had to send them out for microfinishing, then when we got them back we had to send them for DLC coating. We had to buy our own profilometer because about 1/3 of the time one of the two was not done right. We measured them before sending them to be microfinished, then before we sent them for DLC coating, and again when we got them back to be put in an engine.

I cannot discuss exactly what parts we coated, it would be a violation of my contract but I can say it had nothing to do with cylinders or cylinder liners. I'm sure anybody who has kept up with a couple key points would know why.

I have no clue what the cost would be for a single set of housings, many of these places mainly coat medical implants like hip replacements and stuff or do things in large quantities, or for customers who are constantly sending in orders. My only recommendation on cost is to send one of these companies a drawing of what you want coated, with dimensions.

couturemarc

Mazda has been applying coatings on top of the chrome since the mid 80's and this coating has changed several times. The lateset version is similar to a DLC coating.

The coatings decresed friction on a new housing until the coating wore off and also created a better seal and compression on initial start up and break in.

look up some of the old tech papers, Mazda has tried nearly everything to try and make chrome work better for them.

Circuit Theory

iTrader: (52)

we just got an E-shaft back from being "carbon coated". Atleast thats what it is called here in Japan. From what I understand it is the same as DLC. We were told that is chrome can't be treated with this "carbon coating". Does anyone know if DLC can be used on chromed surfaces?

I am still not sure if it is the same process. Our E-shaft came back black after the treatment was applied and will be used in an engine for daily use in order to test it.

The E-shaft we sent was brand new and was not polished or anything prior to sending it off for treatment. If what Kyrasis is saying is true, will this E-shaft rip through the rotor bearings super fast? I will update when I have more info.

c00lduke

Are we worried about how long our housings last under normal conditions? I didn't know any of us were really having a problem with that. At least on our 2nd builds.

Circuit Theory

iTrader: (52)

The test engine is daily driven at 460ps. It will see track useage as well. I guess I should have specified that I just assumed most people consider there RX-7's sports cars and when I said daily use I meant used daily but not in terms of granny driving to play bingo.

Kyrasis6

Some places that do DLC coating will do the required polishing prep work before applying their coatings. We chose a seperate company to micropolish our parts for various reasons. The parts we where DLC coating also had much less oil film if any at all between the wearing surfaces at times of operation. I would imagine that the microfinish on the journals of an e-shaft would be less critical since you have a larger and pressurized oil clearance. Honestly I don't see the reason to DLC coat an e-shaft, all the e-shafts I've seen that cam out of engines with 180k + miles on them have looked new and even had the same surface finish on them as a new one. Really the DLC coating will be more beneficial on surfaces which are prone to failure because of wear, lack of lubrication, or other extreme conditions.