Hydrogen-Assisted Cracking Fracture Analysis using High-Speed Camera and Delayed Hydrogen Cracking Test

Dissimilar metal welds (DMWs) are commonly used when a high strength steel is overlaid with corrosion resistant alloy (CRA) for petrochemical applications. There have been reported failures of these DMWs during subsea service while under cathodic protection (CP). These caused by local hydrogen embrittlement susceptible microstructures that form at the weld fusion boundary. Hydrogen-assisted cracking (HAC) occurs as result and influenced base/filler combinations, welding post-weld heat treatment (PWHT) procedures. A delayed test was to simulate tensile load charging on 8630-FM 625 weld. The failure this sample recorded using high-speed camera capture crack initiation propagation failure. Fractography performed scanning electron microscope (SEM) along energy dispersive spectroscopy (EDS). fracture surfaces, EDS measurement video timestamps revealed brittle nucleation in planar growth CGHAZ regions continued propagate through same leading final ductile (microvoid coalescence) cellular dendritic region