rx7vadim

Tungsten is known to be toughest metal, so shouldnt be a bad idea..

mono4lamar

iTrader: (32)

tungston is used on the space shuttle because it can withstand extreme heat... yet any welder knows how brittle tungston is. if there were any detonation its gone. heck any pulse of energy might crack it. if you drop your tungston off your welding bench its likely to at least crack in half if not 3 pieces. i hope that answers your question.

Kenku

It's also quite dense, which is none too good for the rotor housings... same argument as carbon vs. steel seals.

GUITARJUNKIE28

yea, rotor housings would last like 10 minutes.

TonyD89

iTrader: (10)

I do alot of TIGing. You are so right. Plus it's density would have to great an inertial resistance.

Have you ever noticed how some times, like trying to bend slowly, it seems strong? Do the motion quickly and it snaps like glass.

GUITARJUNKIE28

ceramic coated balsa wood

TonyD89

iTrader: (10)

Plus nitride coating to repel heat, possibly beter than ceramic!

drago86

Except that tungsten isn't known as the toughest metal by anyone but you. Highest melting point of any metal maybe,..

rx7vadim

I Thought It Had Highest Tensile Strength As Well, But I Guees Im Wrong. People Saying Seals Made Of Hard Metals Will Wear Housings, But I Dont Agree With That.. I Havent Heard Of Ceramic Wearing Out Housings..and By The Way Why R Ceramics So Expensive?

Kenku

Tungsten does have a pretty high tensile strength, yeah... but it's brittle. Tensile strength is measured under fairly static conditions... in other words, it's a load applied really slowly. The conditions in the combustion chamber are far from happening really slowly... the forces hitting the seals will peak far higher than the average pressures, and over localized parts will be enough to cause distortion. This is a problem because where steel seals will bend slightly and return to their normal shape, tungsten will start cracking and pretty raplidly just break.

As for hard seals against housings... well, with metallic seals, there's a balance. At high RPM, centrifugal forces start getting signifigant, and it comes to what is going to start having parts of it wear off first; the housings or seals. Ceramics are very hard, yes, but because their density is so much less than the steel seals, the forces are a lot smaller too.

As for costs, I can't say precisely, but I'd imagine part of it is because the same characteristics that make ceramic seals so long wearing makes them hard as hell to machine to the proper size and surface finish. The normal seals are machined with electron discharge machining, which doesn't work for non-metallic stuff... and machining them with any sort of mechanical process is complicated by the fact that the ceramic of the seals is harder than anything except for some grinding wheels and exotic coatings. The other factor is that... it's not like they're mass production items. Noone uses them except some racers... and when the production rate is on the order of a couple hundred per year (if that) the economics of manufacturing say that they're going to be expensive.

TonyD89

iTrader: (10)

^You are correct on many points except the use of EDM to make stock or stock replacement seals. The two piece replacement OEM and aftermarket suppliers like Atkins machine the seals conventionally (you can see the grinding marks). They use a "wire" machine (Electric Discharge Machining through a moving wire) to slice the previously made one piece seal into two. The stock 3 piece seals, I believe through inspection, were completely conventionally machined.

As far as I know, large ceramic pieces like seals are created in a process simalar to sintering. And you are totally correct in the cost of the finishing process which requires the use of diamond tooling and sometimes lasers.

All ceramics made this way, weather for seals or not, are extremely hard, slick, and wear resistant.

Cheesy

There is much less correlation between seal hardness and wear rates than most people realise, in fact different oils can have as much of an effect on seal wear rates as different seal materials. Tungsten is actually very abrasive so it would destroy housings in a similar way to titanium even though the materials have quite different properties

Eson

Cant you change the properties of Tungsten(Wolfram) just by controling the heating and cooling, as you can with steel?. If you heat steel and cools it fast it will be brittle but strong, cool it slow and it will be more flexible.

Matt Hey

What's the point? It would still be heavy and expensive (and maybe abrasive). Tungsten does make a good alloy for steel.

If tougness is wanted then why not try something like S7 tool steel...

.50 C .3 Si .8 Mn 3.3 Cr 1.4 Mo

- Excellent impact/shock resistance hot & cold
- Excellent toughness
- Good softening resistance at high temperatures
- Average wear resistance (good for it's lack of hardness)
- Good through hardening properties
- Good dimensional stability in hardening
- Good machinability
- Can be nitrided, tufftrided, chrome plated, or polished
- Relatively inexpensive (a few dollars material cost for a set of apex seals)

I made a punch at work with S7 that punchs an approximately 8 inch diameter hole in 3/8" A36 plate with the ram of a 600 ton mechanical press. S7 is tough yet cheap and easy to work with. The only downsides I can see are possibly too high of friction (add a friction reducing coating if necessary) and the weight (similar to OEM maybe slightly lighter). S7 apex seals should be very resistant to abuse but would probably still wear out the housings faster than OEM. Theory is not the real world either.

GUITARJUNKIE28

tool steel YO

Tofuball

I say, use Diamond. It's the hardest metal known to man!
http://uncyclopedia.org/wiki/Diamond

Whizbang

bah!


scandium/titanium alloy

Whizbang

minus the whole being a metal thing.

that the the cleavage points on the diamond might make for a bad time when it comes to manufacturing the seals.

1revnrex

Why not just stick with Mazda OEM seals and LEARN TO TUNE.



-Shawn

Valkyrie

Adamantium FTW

Actually, I think something that had flexibility and memory (to protection against detonation), plus low friction (to be soft on the housings) would be the best...

If a seal gets softer with heat, it's all for the better, since it'll seal better that way.

Of course, it can't be too soft, like aluminum, because it wouldn't last as long.

The springs on the other hand need to be stiff, but with memory, and need not soften with heat (so as to maintain compression at high operating temperature). Heat-treated forged steel of a high grade would probably work...

Kyrasis6

High quality tungten weighs about 3 times as much as lead for the same volume, its what the NASCAR teams use instead of lead if they can afford it, which allows them to better allocate the weight.

lol, just to give an idea of what tungsten is like we used Tungaloy inserts for cutting titanium valves at a CNC shop I worked at. A small 5x5x1.5 gladlock bowl full of them weighted a good 15-20 lbs. My first day on the job I went to change an insert in one of the machines and cranked down on the allen bolt and it shattered into a million pieces, the next one I barely finger tightened and it broke after the first cut because I still had it to tight. A tungsten apex seal would be instant disaster, I bet the engine wouldn't even complete a full cycle when you started it up.

Why not use the OEM rings with a Moly insert? The moly would retain oil and definatly help with both sealing and lubrication?

drago86

Ceramics are allready ideal. They just cost too much.

Valkyrie

Ceramics are brittle, too.

Just like ceramic knives... sharp as hell, and hold an edge better than steel, but don't try cutting bone with it, or using it to pry something...

Expensive, too.

TonyD89

iTrader: (10)

HaHa! Tungoly is tungston carbide. Pretty much what is commonly known as "Carbide". And, yes, it is very brittle and hard. Pure tungsten can be most commonly found as TIG electrodes. If you work in a tool shop you may come across "Anvilloy". Trade name for 99.8% pure tungsten. Comes in very expensive bar stock in the flavor of your choice. Machines like ****. Non-magnetic (can't conventionatly surface grind) and can't be EDM'ed. Just try drilling and tapping it for a challenge! You are correct on the wheight thing. This stuff is unbelievably heavy. Way more than lead.

ShadowX

Seriously, Abel Ibarra used OEM seals on his drag cars, well over 1000hp. Sure, he had to rebuild the motors a little more often than us, but it wasn't because of blown apex seals.

Do a search on titanium seals, word is they gouge pretty bad, so they'd eat the **** out of your housings.

Someone should try and make some from that Wootz steel (new Damascus steel). Flexible, strong, hold shape...seems to me they would hold pretty good. One of the trace elements in the alloy just happens to be tungsten!