[MW:13336] RE: 13329] Ductility dip crack

Hi,

Ductility-dip cracking (DDC) is a solid-state, elevated temperature cracking phenomenon observed in thick-section, multipass austenitic stainless steel and nickel-base alloy weld metals where large grain size and high restraint are typical characteristic. This problem is as a dip in ductility within a specific temperature range(Liquid to first solid transformation range) during weld cooling cycle. Although the problem is fairly common, the mechanism of DDC is yet to be clearly understood and good level of research on DDC is on progress.

Researches have indicated, several factors influences DDC such as impurities in the weld (especially S &P) and interstitial element(such as carbides, Nbc especially for 347H) segregation to grain boundaries (GB), grain size, GB orientation related to applied stress, welding parameters, and strain rate. Finer grains with more grain boundary areas tends to arrest DDC. The characterization work conducted to date suggests that DDC is a GB sliding, creep-like phenomenon, which is manifested at intermediate temperatures (usually higher temperatures) where the GB sliding process is activated.

However, the effects of all the above factors are not clear and the DDC mechanism is still not fully understood, which makes eliminating DDC extremely difficult and still is hot research topic.

Please follow the link below for more information.

Thanks

Pradip Goswami,P.Eng.IWE

Welding & Metallurgical Specialist & Consultant

Ontario,Canada.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

http://www.matsceng.ohio-state.edu/wjmg/ductilityDipCracking.htmlx

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of meisam shokri arfaei
Sent: Tuesday, December 27, 2011 8:03 AM
To: materials-welding@googlegroups.com
Subject: [MW:13329] Ductility dip crack

Dear Experts,

Please shortly discuss about ductility dip crack. I know it is relatet to Ni-base alloys and austenitic stainless steels.

Does anyone know another name for this kind of crack?

Regrds

--

M. Shokri Arfaei

International Welding Engineer (IWE)

ASNT NDT Level III

ERI Metallurgy Lab. Manager

Tel: +98-21-66282127

Fax: +98-21-66282779

Please don't print this e-mail unless you really need to. BeGreen!

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