Flexible Ceramic

[thundair]

I am in desperate need of a ceramic to use in a head gasket setting.
I have used Macor with the thousand little pieces after it was run for 20 minutes. I think it actually broke up when we un-torqued the head. (no carbon in the cracks)
we tried aluminum oxide and it broke radially with no particular pattern.
Next we were looking into silicon nitride but it is costly and difficult to find a grinder to put in some 1mm holes that we need.

Thanks in advance for your help

ref:US patent 7299785

I don't know anything but the people that do.

 

[unclesyd]

I would first look at Micanite, a mica based material. Then there are the wet ceramic felts depending on the density you require they maybe the answer.
There are many forms and producers of both materials.

http://www.dimpypower.com/micanite.htm

http://www.icrmica.com/icrmica_micanite.html

http://www.rsifibre.com/products/ceramic-fiber-blanket.php

 

[tomwalz]

Cemented materials such as Tungsten Carbide or other cermets?

We have used them successfully in downhole applications.

There have been huge advances in the last few years.

Tom

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[Compositepro]

I worked with someone who was trying to commercialize head gaskets made from fiberglass fabric impregnated with a silicone resin formulation. There are lots of possibilities but I not too familiar with what the problems are with current designs, and how much people are willing to pay for an improvement.

 

[Ceramicguy]

You have quite a dilemma. Trying to develop a full rim gasket around the combustion chamber in a dense, fine grained ceramic is probably doomed to failure. You have to contend with vibration, detonation, temperature excursions and differentials, variable stress due to distortion or modulus differences etc. The larger the piece of ceramic, the more intractible these issues become. As an alternative, can the "spark plugs" be individual ceramics embedded in a compliant gasket material? I think it was in WW II the Germans developed a method of inserting Pt wires and sintering the ceramic around them resulting in a hermetic joint. The Pt was soft enough at temperature to yield and distribute the stress from the shrinking ceramic. I am not sure who still uses this technology. The last people I knew using this method were Fischer and Porter (the valve makers). Perhaps a ceramic injection molder might be able to redevelop this process. Let me know if you need leads.

Bruce

http://www.accuratus.com

 

[PKerEng]

Sounds like a tough problem. But regardless, first, please define working environment/conditions. You are dealing with thermal mismatch. In addition, tight fit of brittle ceramics is an issue. How hermetic is the seal to be? Mica sheets, as suggested by one of the respondents sounds like something to consider. Also, you may possibly consider inorganic cement bonded compositions. Obviously tightness of the seal will remain always an issue.

Slawomir

http://www.pkerengineering.com

 

[AbyssUK]

thundair, I was just on here looking for some help myself and saw your thread.

Check out Flexitallics sheet thermiculite products, for your application TH866 might be a good bet or TH896 if you need more strength.

http://www.flexitallic.eu/thermiculite®

 

[thundair]

The working environment is a 1000cc twin cylinder Moto Guzzi with the head modified to accommodate the increase in thickness and maintain the original cr. To prototype this was to be the easy part as we were preparing for the difficult engine mapping of fuel and ignition. That said with very little time to run we were able to run with a 14 lambda but no load
The minimum material requirements are dielectric to accommodate 20kv
and working temperature of 500f. The compressive strength eludes me as the numbers worked out for alumina oxide with 6 head bolts distributing across and area about 5" x 5"

I don't know anything but the people that do.

 

[Ceramicguy]

With a working temp of 500F, can you get away with PEEK or other high temperature polymer?

Have you considered boron nitride? It's machinable and low expansion which will reduce the risk of thermal stress failure. Furthermore, it has a low friction coefficient against most materials allowing some slip with thermal expansion mismatch. It also has a relatively low young's modulus to help accommodate small distortions. It should easily meet your dielectric requirements. There are many composites available offering slightly different enhancements to the material properties.

Bruce

http://www.accuratus.com

 

[thundair]

Thanks for the help

One thing to add is the combustion seal is taken care of with .010 soft cooper gasket top and bottom and that works well.

I looked into the boron and silicon nitride both are expensive
I got a quote of 2600.00 for a 92mm ID 98mm OD 3mm thick with 4 1mm horizontal radial holes

I am going to look into the high temperature polymers as they could be the answer now and in production, where as the ceramic are definitely out of the running for production units.

I don't know anything but the people that do.