Can someone id this ceramic

I have two little bricks, about 2x2x7 inches or so, or grey
ceramic. It is easily scratched by knife and can be machined like on a
lathe (I have a few little machined bits of it also). It is a little
bit tougher than regular chalk. The person who sold it to me (in that
big lot of TIG things) told me that it is for making custom nozzles
and high temp stuff. Is there some way to id it?
i
Reply to
Ignoramus11455
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Are you sure it's not a graphite composite? That's a common material for small rocket nozzles.
LLoyd
Reply to
Lloyd E. Sponenburgh
Lloyd, it is a good question. It does not look similar to graphite used in, say, pencils. (scratches a little bit differently), but it is a very interesting guess, I will investigate tonight. I saw some ICBM reentry vehicle heads before, made of graphite, those were considerably darker. Anyway, it is a very interesting line of thought.
i
Reply to
Ignoramus11455
Greetings Ig, McMaster-carr sells a machinable ceramic that seems to fit your description. After machining it must be fired. I have machined the stuff in the past and fired it. However, it's been about 8 years since I messed with the stuff so you will need to go to the Mcmaster-Carr web site yourself to find it. Cheers, Eric
Reply to
Eric R Snow
Eric, yes, McMaster items like 8479K1 seem to fit the description. Light gray color. Thanks. They call it (if I got it right) general purpose alumina silicate ceramics. My pieces are approximately 2x2x9 inches, if I recall correctly, I am going by memory.
i
Reply to
Ignoramus24559
Probably "lava", alumina silicate. A long and detailed firing procedure. It turns pink and either grows or shrinks when fired, I forget. Randy
Reply to
Randy Replogle
Yes, looks like you are 100% right.
i
Reply to
Ignoramus24559
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It has a very faint smell like gypsum or concrete.
i
Reply to
Ignoramus11455
According to Ignoramus11455 :
Sounds like what I have heard called "lava rock". You machine it to the desired size and shape, and then fire it, and it turns a pink color and becomes *very* hard.
Nice stuff for some things -- and I believe that is used to make the gas cups used in TIG and MIG guns.
I used it to make a reducing bushing for the thermostat probe for my heat-treat oven.
Enjoy, DoN.
Reply to
DoN. Nichols
Don, thank you as always, I think that you are right and that's "it".
i
Reply to
Ignoramus11455

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