why doesnt anyone make apex seals from 6al4v titanium? at first glance it would seem almost ideal. the thermal expansion is as low as cast iron, excellent hardness, tensile and yield strength. also would be very lightweight compared to iron for keeping the seal on the housing better. you could even run a lighter spring for less wear. melting point is >3000F so that is great too. material costs are not too bad though machining costs would be high. im sure it would end up cheaper than ceramic seals though. hopefully someone can fill me in on this.

 

Ti is quite flexible. You can get around this in most applications (like, say, bike parts ) by making the parts physically larger (huge diameter tubes or otherwise large cross sections) but obviously we can't really do that for a replacement apex seal since it has to be a fixed dimension.

Another problem is that Ti loves to gall. LOVES to gall. Again going back to the ol' bike shop, ask any bike mechanic worth a crap how much anti sieze he puts on threaded titanium parts. What does the apex seal do? It slides in and out of its slot constantly and it has a leaf spring pushing on its backside. Oh yeah, and it also rides against the inside of the rotor housing!

A thrid problem is that Ti is crack prone. Any surface imperfection will lead to cracks more quickly than with iron. Again, for bike parts, you just design the parts with enough material so it's not so stressed. But then again, how many people stopped using Ti pedal spindles after they broke a pedal off? (Bearing stratches Ti, Ti cracks, rider discovers joys of walking/limping home bleeding)

 

Someone just R&D'd some titanium apex seals 5 months ago maby on this forum, he ran the motor for a very short period of time, shut id down, enngine now had low compression, after tera down the rotor housings looked as iff they had many many MANY years of use out of them. Search this forum, its not to old of a thread

 

what about inconel???

625 Inconel, containing approximately 60% Nickel and 22% Chromium, was developed to cope with the extreme heat and strength demands of jet engines.
Molybdenum and Nobium elements also contribute to 625’s strength at temperatures greater than 1800º F, where 321 SS is unsuitable.
Inconel 625 excels in applications such as Rotary engines and extreme duty turbocharger exhausts

in summary, its the best stuff to make exhausts out of.

what about a apex seal made of that.

what are the desired properties of a Apex seal metal.

Ceramic still seams like the best option.

 

the fact is MAZDA has been researching Apex seal material for over 40 years and has yet to find a material that gives a better combination of workability, sealing, wear and strength properties than the current seals. regarding INCONEL I believe it also has poor galling properies in sliding/friction applications. One of the prime considerations for an apex seal, is a material that wears well w/o destroying the ROTOR HOUSING, a much more complex and expensive part of the engine.

 

One of the properties I would want is for the seal to wear before the housing. I'd rather have to replace worn-out seals than worn-out housings.

 

Theres a thread like this every month or so, Ti is a bad choice, someone triend it, turned out bad like we warned him. Ceramic is the best solution, but is expensive. Apex seals need not only lightness, strength and temperature resistance, but good frictonal/wear properties, something TI, nore Iconel were designed for.

 

ah yes galling. i should have known from my experience on my mountain bike. does anyone know what type of ceramic is used?

 

mr Lasse Wankel tried this I think. You should ask about his experience

 

so is the stock seals and ceramic seals the only material that can be used for apex seals.....what about (crazy idea) diamond seals? does diamond have good properties to be an apex seal?

 

you could make a synthetic diamond seal, but the housing would be gone after about 10k revolutions.

Diamond is the hardest substance on the planet, which not only destroys the comparably softer Housing but would crak easily under detonation

 

oh ok....so what else can be used to make apex seals other than ceramic and steel and that carbon stuff?

 

where the Ti seals ceramic coated. flu is kickin my *** tonight, so il ask instead of search on google, what about a teflon compound coating?
I know they make piston skirts out of teflon, but i thought teflon was good only to 500*F or so. how about a teflon nickel compound or similar approach, too much metallurgy, and niquill is starting to kick in..

rant off

 

lol get well buddy.....i failed chem(almost failed) so i dont have any comments bout this