SEDL / STP / STP1401-EB / STP10233S

The Use of Atomic Force Microscopy to Detect Nucleation Sites of Stress Corrosion Cracking in Type 304 Stainless Steel

Brongers, MPH
Project Engineer, Senior Group Leader, and Senior Scientist, CC Technologies, Dublin, OH

Koch, GH
Project Engineer, Senior Group Leader, and Senior Scientist, CC Technologies, Dublin, OH

Agrawal, AK
Project Engineer, Senior Group Leader, and Senior Scientist, CC Technologies, Dublin, OH

Pages: 17    Published: Jan 2000

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Abstract

The nucleation of intergranular stress-corrosion cracking (IGSCC) in Type 304 stainless steel was investigated using atomic force microscopy (AFM). A new test technique with an AFM fluid cell and a miniature specimen bending device was used for the in-situ measurements. It was found that upon plastic deformation of the annealed and sensitized stainless steel slip lines piled up at the grain boundaries. As a result of the increased localized stresses, some of the grain boundaries opened, particularly at grain boundary triple points and grain boundary — twin boundary intersections. These openings were typically 1 to 2 μm wide and about 1 μm deep. After exposure of the specimens to an aqueous 1000 ppm sodium thiosulfate solution small cracks (< 1 grain diameter) formed from the opened sites within a few hours of the exposure. This indicated that the opened triple points act as nucleation sites for the cracks.