Trim Material on CSCC environment 1

[Xeros]

Hi,

SS type 316 contact with chloride could experience Chloride Stress Corrosion Cracking and I know that CSCC is embrittlement cracking.
therefore, SS type 316 is susceptible for CSCC.

However, I think that valve trim is forged material and forged material is not susceptible for embrittlement cracking, not plate material.

how about your opinion?

and what kinds of valve trim materials could be recommended for CSCC environment if my opinion is wrong?

 

[strider6]

in my opinion there is a little confusion..
CSCC in not an enbrittlement cracking (in terms of an hydrogen enbrittlement mechanisms) and a forged materials has no advantage over a plate materials in terms of resistance to CSCC. Forged materials are less sensistive to HIC but this is another issue.
an upgrade of you materials coulb be a copper-alloy or nickel-alloy.
S.

http://www.corrosionist.com

 

[EdStainless]

The reason that it is uncommon to see CSCC in forged valve parts is that they are so over designed that the stresses are low enough to avoid SCC.
Your best bet is to mover to high Ni alloy. As you move to higher Ni levels the threshold temperature for CSCC increases. When you get above about 40% Ni you will be safe from CSCC.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[EdStainless]

I guess that I should add a bit of further explanation. In practical terms the duplex grades (2205 and 25%Cr) and the 6% Mo Super-Austenitic grades (AL-6XN, 254SMO, 1925hMO) all have useful resistance to CSCC. They can be cracked, but hte Cl level, temperature and stresses required are well above the levels for the 300 series alloys.
It is often more cost effective to use one of these alloys and design for lower stress than to go to a Ni based alloy.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube