Fracture Failure Analysis of 304 Stainless Steel Bolt in Chemical Plant Onshore

This paper presented the fracture failure analysis of 304 stainless steel bolt that was in service in an onshore pipeline with medium pressure, normal temperature and non-corrosive. The fracture of the bolts was not due to obvious plastic deformation. Based on the scanning-electron microscope (SEM) findings, a lot of carbide distributed in boundary of the grains, which was primary Cr-carbide. All cracks were indicative of intercrystalline fracture. The corrosive element of chloride was above allowed standard as detected in fracture surface by energy-dispersive spectrometer (EDS). In addition, the analysis showed that some lath martensite formed since the bolt was fabricated by cold-drawing, which made it be more sensitive to SCC. Given all that, one conclusion was drawn that the failure cause of the stainless steel bolt was attributed to intergranular stress corrosion cracking (IGSCC).