Bentonite Abradable-Erosion Testing
02-18-2008, 06:06 PM,
Bentonite Abradable-Erosion Testing
I have had a hard time finding parameters for Metco 312 (Bentonite). We flame spray it here, because "you can't plasma spray 312". This is the word around here.

We are applying Metco 450 bond with about .030" topcoat of Metco 312. This coupon is then tested for errosivity, which the limits are 5-12 sec/mil. We have changed A LOT of parameters and performed a lot of testing, but we seem to never reach above 6 or 7 on the erosion test..and honestly we fail this test frequently.

Does anyone know what direct controllers are for erosion testing? Hardness, density, etc...??

This coating seems to be tough on me, it seems to change with seasons even. Thank you.

02-19-2008, 02:48 AM,
RE: Bentonite Abradable-Erosion Testing
Hi John

The only parameters I have are for the Metco 6P gun, which I'm sure can be reproduced with the 6P-II. Typical hardness claim 60 (+/-5) HR15Y.

Nozzle P7A-M, Siphon plug 6P 205, Air cap cool side out.
Oxygen 45 Flow (GF Flowmeter) @40 psi
Acetylene 55 Flow (GF Flowmeter) @ 15 psi
Air @ 15 psi
Nitrogen carrier gas 37 flow (MFR 3MP, 4MP etc.) @ 55 psi
Spray rate 8.5 lb/hr
Spray distance 8.5 inches

Spray rate and spray distance are said to be critical.

Adjustments to achieve correct hardness basically is to increase acetylene flow to increase hardness and decrease acetylene flow to decrease hardness.

Engine shroud segments are recommended to be sprayed at 250 sfpm with gun traverse of 0.25 inches/rev to give 0.002 - 0.004" per pass.

Not familiar with your erosion test, but usually hardness is the direct controller.

Hope that helps

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