Standard for peening to prevent stress corrosion cracking

[kevlar49]

Is there an industry standard that I can quote for peening of stainless steel to minimize/prevent stress corrosion cracking.

I would like to use this for mitigating Cl SCC on a solid stainless steel lube oil cooler that occassionally has to be sprayed with water to help with additional cooling.

(lube oil must be in contact with stainless for product cleanliness) I can paint, but it is likely to deteriorate. Duplex is cost prohibitive.

Any help would be appreciated.

 

[gr2vessels]

kevlar49,

Peening is indeed allowed under UW-39 and AF-234. However, it is common practice to ban the peening on the Stainless Steel pressure equipment and particularly on welds (including the Austenitic Stainless Steel pressure parts), as the peening could be an initiator for SCC. In fact, most of the O&G major specifications (Shell, BHP, etc) are simply banning the peening altogether, to avoid the risk of misinterpretation and potential damage to the pressure equipment.
As the standard for the peening process, I could help only with an Australian reference, if it is of any use to you.
Also, I would think that you should have many more replies, perhaps better ones (hey, boys!!)

Cheers,

gr2vessels

 

[metengr]

Just a bit of nomenclature; mechanical peening is normally used during welding to relieve residual stresses between passes. Shot peening, which uses steel shot to induce a residual compressive stress along the striking surface, has been well documented to increase resistance to CSCC in austenitic stainless steels (Ref; "Corrosion of Stainless Steels" by John Sedriks.

The problem is that the entire surface needs to be shot peened to be effective, not just the weld or base metal HAZ. This can be very costly, and is not really practical for vessels.

 

[MikeHalloran]

Buy a bigger/ better/ additional cooler, and reassign the guy with the hose to more productive duties.


Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

Your other option is to use the correct grade of stainless. Consider using 439 instead of 304. Then CSCC will not be a concern.
Is a lean duplex really more expensive than unit fialures? Don't only look at 2205, LDX2101 might be a good alternative. Ifyou look at duplex make sure that you also look at making the walls thinner, since the alloy is so much stronger.

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http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[unclesyd]

I did a lot of work in the early 60's with shot peening to mitigate IGC, where it was the primary mode of attack, and Cl/SCC in 304L SS in HNO3/Organic service. The results were quite good on components where the surfaces were exposed for shot impacting. As stated above coverage is problem over large areas.
My results in migrating Cl/SCC were quite varied. Laboratory work went very well while the field test left a lot to be desired except in a few cases. Tests in salt water were inconclusive.

http://www.metalimprovement.com/stress_corrosion_cracking.php

Go to this page and type in SCC.

http://www.shotpeener.com/library/index.html

Laser Peening:
Just before I left I had procured some Laser Peened samples of 304L that were showing excellent results in mitigating Cl/SCC in the lab. I had a few centrifuge parts Laser peened but have since learned that they were never installed.