Magnetic Permeability
12-10-2009, 07:04 AM,
#1
Magnetic Permeability
Hi everyone,
we have problem on Magnetic permeability of coating.
we are spraying Metco 136 F top coat with Metco 450NS bond coat on Nitronic 50 Steel for down hole applications.
Our vendor has asked for " Magnetic Permeability of coating 1.005 max(field strength 200 OERSTEDS)
1.What is the method for testing Magnetic Permeability of the coating?
2.Is there any method to reduce the Magnetic Permeability of the coating.
regards
Ravi
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12-10-2009, 03:22 PM,
#2
RE: Magnetic Permeability
Hi Ravi

Quote:Magnetic Permeability of coating 1.005 max(field strength 200 OERSTEDS)
I assume this is relative magnetic permeability

Quote:1.What is the method for testing Magnetic Permeability of the coating?

ASTM A342 / A342M - 04 Standard Test Methods for Permeability of Feebly Magnetic Materials

Quote:2.Is there any method to reduce the Magnetic Permeability of the coating.

This will mainly be dependent on choice of coating materials. Metco 136 F coating should be ok, but Metco 450NS, I think not, as coating is essentially nickel and ferromagnetic. Alternative base coats to consider? maybe molybdenum, 80/20 NiCr, inconel 625, titanium (no guarantee though Rolleyes )
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12-16-2009, 07:02 AM,
#3
RE: Magnetic Permeability
Dear Gordon,
thank you for your reply.
Does the porosity in the coating have to do anything with the magnetic permeability.
If so what is the method to obtain minimum porosity in the coating we are getting around 2 to 3 % porosity.
we are using Metco 9mb Gun with argon and Hydrogen as primary and secondary gases and are following Sulzer Metco recommended parameters for the Bond Coat (450NS) and Top Coat 136F.
regards
Ravi
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01-05-2010, 04:58 PM,
#4
RE: Magnetic Permeability
Hi Ravi

Small changes in coating density, air/organic sealer content I think will have little effect on the magnetic permeability. Making the right choice of coating material is going to be the most critical factor. Bond Coat 450NS will be a ferromagnetic coating and will not be suitable. Also, remember not all low magnetic permeability materials will necessarily form low magnetic permeability coatings. Your typical 316 austenitic stainless known for being non-magnetic in normal condition or powder form, but often becomes somewhat ferromagnetic as a thermal spray coating.

I would strongly suggest testing all potential coatings (not just powders before spraying) before any commitment. Post coating treatment like heat, machining, cold working should also be considered as these can also effect/change magnetic properties.
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02-04-2010, 09:37 PM,
#5
RE: Magnetic Permeability
Search for "magnetic permeability meter". I have had great success with this meter. You will have to dedicate a powder feeder for your Chrome Oxide (to avoid cross contamination). I've used Starck's 250.2 (coating thickness = 0.5 - 3.0 Mils) and Starck's 704.1 (finished coating thickness = 10-15 mils) and met the 1.005 criteria. Also, use caution when conducting the inspection - ANY ferro materials near the inspection point will cause false readings.

Good luck.
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02-05-2010, 02:41 AM,
#6
RE: Magnetic Permeability
Hi Miswa

Sign0016 to the Surface Engineering Forum.

Thanks for your input.
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