Looking For A Special Dielectric Coating

Hi BruceAA,

there is a need for more information:

plastics may be durable and scratch resistant to some extent and low in friction: teflon-glass or teflon-mica or torlon-graphite are examples,

ceramics may be better in certain situations: iron oxide on steel, alumina on copper and many more, (high friction if dry - low friction if wet),

also nitrides, borides silicides and naturally the sulfides.

So: what shall the dielectric coating be used for: insulation only, capcitive behaviour, which voltage, frequency, damping,

which parts: size, shape, weight, velocity, lubricant,

RHABE

Might try Beryllium copper, machines annealed, hardens to up to RC48 and 200Ksi.

Very good conductor though.

Brad

What about the conductivityof the BeCu? Also what percentage doped is the copper?

BeCu is the actual material that we currently use; but it's a coating for the BeCu that we are actually looking for. In our application we apply a hi voltage (approx. 5,000V) to the BeCu and insert a conductive piece of metal through a hole in the BeCu. The clearance between the BeCu and the conductive metal is very small and without some sort electrically insulatative coating between the two, there is a short circuit. We need to keep the clearance as tight a possible, so we're looking for a coating that we can apply and then machine off to allow a slight (almost interference fit) between the BeCu and the conductive metal without allowing a short circuit to occur. If the coating has good slip characteristics then that's a plus, but it must be able to withstand a million cycles of the conductive metal being inserted and re-inserted into the BeCu.

Thanks,

Bruce

Dear Bruce AAA,

how can you put 5KV across a "clearance between the BeCu and the conductive metal is very small" ? This will give arcing if the voltage is above 300V (at atmospheric pressure).

Only at high vacuum pressure this may be better but in that region of pressure gaps of 0,5mm are used for insulation.

What is the size of the conductive insert?

May be you should change to a ceramic insert with a conductive coating inside?

RHABE

Hi Ben56,

the original question was for a dielectric but CuBe is a conductor.

CuBe is most often used as CuBe2 that is 2% (weight) Beryllium.

This is reducing electrical conductivity to only (near) 30% of pure copper!

So if use as conductor is requested then it is useful to use CuCoBe or CuNiBe.

These alloys need a completely different thermal treatment, have less strength but a much better electrical conductivity.

RHABE

I do not recall if you called out the dimensions of the part you are working with.

There are some machinable ceramics in the market that are very durable.

Micaver (400^oC) and Micaver HT (700^oC) can be machined to tight tolerances.

If the components are the appropriate size, you can insert mold metalic parts with Micaver. You achieve a tight metal to ceramic seal. The CTE is similar to SS so there are no issues with breaking this tight seal at high temperatures or cycling.

Mycroy is an alternative, so is Macor, but my company does not make those ceramics.

Thank you for this comment (which is starting to get on track for our application). Let me address a few of your thoughts:

1- the part size is about 2" wide x 12" long x 0.3" think with 10 - 0.50" holes bored thru the thinkness at about 1.0" on centers.

2- thermal is not an issue for us as the unit will operate less then 100 deg F.

3- the issues we are concerned with for the coating in order of importance are:

a- electirical resistance to 5,000 volts with a thinkness of ~1mm

b - machinability to end up with ~1mm gap between the inserted piece of metal and the coated part.

c - durability (scratch resistance) from a plastic part that will slide thru the 1mm gap.

d - as slippery of a suface as possible to limit frictional resistance when sliding the plastic/ metal part thru the gap.

If you (or anyone) have any thoughts as to the best coating for this purpose, we'd eally appricate it.

Have a great Holiday Season and thank you for your assistance.

Bruce

Hi,

5000V across a gap of 1mm?

This is possible but not in air at normal conditions.

Beware the rims.

RHABE