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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
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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
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Product Number: 51322-18143-SG
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