Alloy 718 - Api 6a cra / B637 - ams)

[Johnwoo1991]

Is it a problem in your opinon if i declare on valve general drawing for approval as a stem material ASTM B637 UNS N07718 (which should be similar to ams standards) and then i produce the valvole stem with an alloy 718 certififed to API 6A CRA? Isn't it better one for oil & gas aplications or can it cause issue for material test certificates review?

 

[EdStainless]

If you call out a spec then you are obligated to meet all of the requirements of that spec.
You can't just use the same UNS with 'similar requirements'.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[MagBen]

Technically (not representative of a quality engineer) 718 can and is being used for oil & gas applications still meeting the maximum hardness requirements of the NACE, but normally with less Nb addition and a higher temperature heat treatment for a better corrosion and a bit compromised strength.

 

[EdStainless]

There are three different heat treat conditions for this alloy.
One maximizes strength, one maximizes creep, and the other gives improved SCC resistance.
You have to get this right for your application.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed