718 and Galling?

[Hush]

I want to use Inconel 718 for a valve stem and gate nut but need to know a few things first.

Is 718 susceptible to galling?
If it is will copper plating the nut threads help or will this cause other problems?
Will 718 (approx 18% Fe)take a nitride?

Any help would be appreciated.

 

[knobhead]

As far as I know 718 won't gall, though I stand to be corrected on that.

718 won't nitride, in that if you nitride it it has no (noticable) effect on the material. Excessive accuaracy is a sign of poor breeding. -Socrates.

 

[acampbell]

Bead blast and then copper coat that should do the trick

 

IN 718 is sususceptible to galling. Though you can not Nitride 718, there are other surface modification such as Boronizing and Aluminizing that will provide a gall resistant layer at the surface. Also, chorme plating will work.

Feel free to contact me if you would like to discuss your applications or these solutions in more detail (matt.hinckley@tmtresearch.com).

 

[TVP]

The person from TMT is correct, Alloy 718 is susceptible to galling, so you need to take this into consideration. Depending on the nature of your application (temperature, availability of lubrication, etc.), you may want to consider other coating options like Diamond Like Coatings, or just a high-temperature capable lubricant (MoS[sub]2[/sub], etc.)

 

[Hush]

The application is a valve stem. H2S 27%, CO2 24%, wet, high chlorides, 200 F, 10,000 psi. Initially lubricated but that won't last long in this environment.

Any comments on how well a XYLAN coating is likely to stand up as an anti gall coating?

 

[TVP]

I'm not an expert on XYLAN, but you may want to investigate the 1305/15 formulation-- good resistance to elevated temps, bases, salt. I can't comment on H2S or concentrated Cl-. I would definitely be looking at high performance coatings like DLC or tool type coatings-- TiN, TiCN, etc.

 

[BarryMartin]

Why not try silver plating the threads?