Anyone have experience with thin hard faced coating called Armoloy TDC or XADC?

[johnchrc]

Application is for use on Test Caps and Plugs used to pressure test assemblies with premium self sealing buttress type threads without damaging either the assembly or test equipment. This would be to prevent galling. The threads on these assemblies are casing threads and are made to be made-up several times at most. We get away with more now because we use lower torques or low-torque thread form test cap options. The threads are peened for galling resistance and the box threads are phosphated. That is OK for the assembly but the test cap and plug will eventually wear out then problems occur.

I like what have read about TDC and XADC (78 and 98 RC respectively). I do worry about cracking in the thread root radius. I was wondering if this would be a good alternative. Material is 110 ksi MYS 41XX LAS with 36 Rc. Perhaps case hardening is option.

- CJ

 

[TVP]

Hard chromium electroplating of casing threads will be challenging, due to the small/non-existant root radius, tall thread profile, etc. Have you investigated a bonded, dry film lubricant/coating such as Dow Corning Molykote, Everlube from CWST, etc.?

 

[johnchrc]

Yes. Thinking about Molycote 4300 or is it 3400?

- CJ

 

[johnchrc]

Also, I'm just doing test fixtures. I care about the thread flanks being coated. but I do worry about cracking at the radius. I will probably try Molycote on another size.

- CJ

 

[TVP]

Molykote 3400A is a very good product.

 

[johnchrc]

What vendor do you use for the 3400A

- CJ

 

[TVP]

Here are two sources for your consideration:

http://www.decc.com/dow_corning.php

http://www.suncoating.com/dow-corning-molykote-Industrial-Coating.html

 

[tbuelna]

It is generally a good idea with threaded connections to make sure the part that is easier/cheaper to replace has lower strength. It also helps to prevent galling in thread connections if one component is harder than the other. However, if there is any appreciable amount of interference in a thread connection, no surface coating, no matter how hard, will prevent galling.