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<p>Failure analysis of a cold-formed S30408 stainless steel head revealed intergranular stress corrosion cracking (IGSCC) originating from outer wall, with stable propagation zone covering 69.7% of fracture surface. Corrosion products (β-FeOOH, FeOCl, NiCl₂·6H₂O) confirmed Cl⁻ enrichment and acidified crack tip environment. Root cause was omission of solution heat treatment as required by GB/T 150.4-2024 (Chinese national standard, equivalent to ASME VIII-1), leading to retained residual stress and microstructural instability. Electron Backscatter Diffraction (EBSD) analysis showed micro-sensitized initiation zone with high dislocation density, 11.7% strain-induced martensite, and 71.6% low-angle grain boundaries (LAGBs). Grain boundary characteristics controlled cracking: LAGBs dominated in initiation (71.6%) and propagation (66.9%) zones, while high-angle grain boundaries (65.7% HAGBs, 39.0% Σ3 twins) in termination zone acted as barriers. Microhardness decreased from 264 HV (initiation) to 195 HV (base material), consistent with EBSD strain parameters. This study provides crystallographic evidence for IGSCC in cold-formed austenitic stainless steel under chloride environments.</p>

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Microstructure Characterization and Failure Mechanism of Stress Corrosion Cracking in a Cold-Formed S30408 Stainless Steel Head

  • 期刊论文

  • 发表日期：

    2026年6月26日

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  • Ting Yu,
  • Shijie Xie,
  • Zhongwei Wang,
  • Daozheng Nie,
  • Zhezhen Dai,
  • Chao Peng,
  • Liming Wang,
  • Kaifei Wu

摘要

Failure analysis of a cold-formed S30408 stainless steel head revealed intergranular stress corrosion cracking (IGSCC) originating from outer wall, with stable propagation zone covering 69.7% of fracture surface. Corrosion products (β-FeOOH, FeOCl, NiCl₂·6H₂O) confirmed Cl⁻ enrichment and acidified crack tip environment. Root cause was omission of solution heat treatment as required by GB/T 150.4-2024 (Chinese national standard, equivalent to ASME VIII-1), leading to retained residual stress and microstructural instability. Electron Backscatter Diffraction (EBSD) analysis showed micro-sensitized initiation zone with high dislocation density, 11.7% strain-induced martensite, and 71.6% low-angle grain boundaries (LAGBs). Grain boundary characteristics controlled cracking: LAGBs dominated in initiation (71.6%) and propagation (66.9%) zones, while high-angle grain boundaries (65.7% HAGBs, 39.0% Σ3 twins) in termination zone acted as barriers. Microhardness decreased from 264 HV (initiation) to 195 HV (base material), consistent with EBSD strain parameters. This study provides crystallographic evidence for IGSCC in cold-formed austenitic stainless steel under chloride environments.