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Failure Analyses On A Super Duplex Stainless Steel Tube Material Before And After Slow Strain Rate Testing In Sour Conditions – Part 2: A Case Study On Local Corrosion

Failure Analyses On A Super Duplex Stainless Steel Tube Material Before And After Slow Strain Rate Testing In Sour Conditions – Part 2: A Case Study On Local Corrosion
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The investigation on the specimens in the SCC susceptible conditions is included in Part 1, AMPP conference paper C2022-179982. In this Part 2, a case study is presented on the local corrosion on specimen surface or shoulder area although high ductility ratios in two testing conditions.    

Product Number: 51322-18320-SG
Author: Wenle He, Raveendra Siriki, Jerry Lindkvist
Publication Date: 2022
Industries: Science of Corrosion , Corrosion Monitoring and Control , Coatings
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$20.00
$20.00

A failure analysis has been performed  and discussed in Part 1 on the tube material of UNS S32750 and the specimens which showed SCC susceptible after the SSRT in a sour environment in pH 2.8, pH 3.5 at 80 °C.

In this Part 2, a case study has been performed on local corrosion on surface corrosion attack observed on two specimens. Scanning electron microscope (SEM) equipped by energy-dispersive X-ray spectrometer (EDS) analysis and Electron backscatter diffraction (EBSD) measurements have been used. On a specimen tested in pH 2.0 at 50 °C, selective dissolution (SD) has been identified in austenite and thin uniform corrosion on the surface in ferrite, no crack has been observed under the corrode surface. On a specimen tested in pH 4.5 at 80 °C, both SD and cracking have been observed under the line corrosion in shoulder area. EBSD revealed that micro cracks initiated in ferrite with enhanced strain/deformation in frontend of selectively dissolved austenite. Dry-wet condition is supposed, which would make the local condition of a thin liquid layer more severe compared to the bulk liquid testing condition. The surface analysis methods showed a good way for failure analysis, which might be helpful in other complicated cases. 

A failure analysis has been performed  and discussed in Part 1 on the tube material of UNS S32750 and the specimens which showed SCC susceptible after the SSRT in a sour environment in pH 2.8, pH 3.5 at 80 °C.

In this Part 2, a case study has been performed on local corrosion on surface corrosion attack observed on two specimens. Scanning electron microscope (SEM) equipped by energy-dispersive X-ray spectrometer (EDS) analysis and Electron backscatter diffraction (EBSD) measurements have been used. On a specimen tested in pH 2.0 at 50 °C, selective dissolution (SD) has been identified in austenite and thin uniform corrosion on the surface in ferrite, no crack has been observed under the corrode surface. On a specimen tested in pH 4.5 at 80 °C, both SD and cracking have been observed under the line corrosion in shoulder area. EBSD revealed that micro cracks initiated in ferrite with enhanced strain/deformation in frontend of selectively dissolved austenite. Dry-wet condition is supposed, which would make the local condition of a thin liquid layer more severe compared to the bulk liquid testing condition. The surface analysis methods showed a good way for failure analysis, which might be helpful in other complicated cases. 

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Failure Analyses On A Super Duplex Stainless Steel Tube Material Before And After Slow Strain Rate Testing In Sour Conditions – Part 1: SCC Susceptibility
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Failure Analysis On A Super Duplex Stainless Steel Tube Material Before And After Slow Strain Rate Testing In Sour Conditions - Part 1: SCC Susceptibility

Product Number: 51322-17998-SG
Author: Wenle He, Raveendra Siriki, Jerry Lindkvist
Publication Date: 2022
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Standards NACE(1) MR0175 / ISO(2) 15156-31 have temperature-H2S-Cl-pH limits for safely using duplex stainless steels based on their Pitting Resistance Equivalent Number (PREN) of subcategory such as duplex stainless steel (DSS, PREN 30-40, Mo>1.5%) and super duplex stainless steel (SDSS, PREN 4045), temperature-pH domain of stress corrosion cracking (SCC) resistance can be used for material evaluation and provided by using slow strain rate testing (SSRT) screening in sour testing conditions2. 
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Failure Analysis Of 4-Inch Welded Fittings In Treated LPG Service

Product Number: 51322-17850-SG
Author: Sudhakar Mahajanam
Publication Date: 2022
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Caustic stress corrosion cracking (SCC) is known to occur in carbon steels under tensile stress and exposure to caustic solutions from 115°F to boiling temperatures. Alternating wet and dry conditions tend to increase SCC susceptibility. Localized overheating of the metal, such as solar radiation, heat tracing, steam outs and excursions should also be considered. Caustic SCC was first reported in 1980 when the top of a continuous kraft digester vessel blew off in Pine Hill, Alabama. It was found that the tensile residual stresses present in non-stress relieved carbon steel weld seams and the corrosive environment (caustic) were responsible for the cracking
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11294 Susceptibility of Hydrogen Induced Stress Cracking of Duplex Stainless Steel at Elevated Temperature

Product Number: 51300-11294-SG
ISBN: 2011 11294 CP
Author: Roy Johnson, Bard Nyhus, and Ole Edvard Kongstein
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Experience has shown that stainless steels can suffer from Hydrogen Induced Stress Cracking (HISC) under cathodic protection in seawater.  This paper presents results from a test program examining the HISC susceptibility of 25% Cr super duplex stainless steel (UNS S32750) at temperatures up to 1500C.
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