Galling 2

[JohnsonMadukayil]

We are trying to subject a safety valve to a functional test of 670 cycles of performance. And we notice gall setting in at the sliding contact surfaces (after a few cycles) which are typically SS 316/SS 316/SS 316. We changed this to Nitronic-60/SS 316/SS 316. And Nitronic - 60 is safe. But 316 has gall setting in. And Nitronic-60/Nitonic-60 combinations are not recommended by Armco.
Any suggestions as to what materials should be used/or at the interface/or regarding tolerancing to reduce gall......?

 

[mcguire]

You can improve upon nitronic 60/316 by using nitronic 60/304 or 303. You could also do better with a martensitic such as 410, 416, or 440C. 440C would be best of all.
For data see the ASM Metals Handbook, section 15.5.

 

You may also try a coating or a surface conversion. We offer a couple of options that may work for this applications. See

http://www.tmtresearch.com

or contact me directly if you are interested (matt.hinckley@tmtresearch.com)