Dear George.
In our project, we ordered some X52 pipes that internally claded& weld overlaid with INCONEL 625 and for qualification of welding procedure, we want to do ASTM G 28 for detecting of susceptibility of inter granular corrosion.
Now some issues arised:
1.Acceptance criteria that we have found in major documents such as " R Baboian, Corrosion Tests and Standards: Application and Interpretation, ASTM Manual Series MNL 20, second edition, 2005, ASTM, PA, USA" said 0.8 or 0.9 mm/year that but in TOTAL specification of "GS EP PVV 618"say 3mm/year(ideally 1-1.2mm/year). which of them is reliable and when the other can be chosen?
2.Sample preparation not specified in the standard in through thickness direction and I don't know how to prepare it. is it necessary to prepare samples from whole clad(3.7 mm that included interface) or 1 mm from cap surface of clad is enough or other option? this question arises from this point that IGC comes from carbide & inter metallic that mostly possible in diluted area . Now is it reasonable to prepare sample that interface involved it or not?
"The intent is to test a specimen representing as nearly as possible the material as used in service. The specimens should be cut to represent the grain flow direction that will see service, for example, specimens should not contain cross-sectional areas unless it is the intent of the test to evaluate these. Only such surface finishing should be performed as is required to remove foreign material and obtain a standard, uniform finish as specified in 6.4. For very heavy sections, specimens should be maintained to represent the appropriate surface while maintaining reasonable specimen size for convenience in testing. Ordinarily, removal of more material than necessary will have little influence on the test results." this paragraph is taken from G28 and only said about the surface area but didn't talk about any thing about cross section or through thickness orientation of sample especially for weld deposited over laid that have a metallurgical & diluted interface can rise possibility of detrimental phase.
Would you share your experience or address me to a document that specify this issue?
Regards.
On Sat, Sep 22, 2018, 4:53 PM George Dilintas <dilintas@gmail.com> wrote:
it depends on the corrosion rate and some allowance for dilutionΣτις Δευ, 23 Ιουλ 2018 στις 5:24 μ.μ., ο/η Ali Asghari <asgharialigl@gmail.com> έγραψε:Dear All.--Does anybody know about how a designer calculate the thickness of clad material especially for sour service and how much is conservative?because in our project documents have not said clearly that thickness of clad have to be measured from base material or from layer that dilution is negligible and this question remained does designer account or consider dilution or not?Regards.
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----Dr. Georgios Dilintas,Dipl. Ing. In Aeronautic and Space EngineeringPh.D in Mechanics of Solids - Computational MechanicsA.I.S, A.N.I, IRCA Lead AuditorWelding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis
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