Stress-based hydrogen damage model of X80 pipeline steel and its damage risk assessment under cathodic interference

In this paper, the crack propagation behaviors of X80 pipeline steel under different cathodic current conditions were investigated by constant displacement loading experiment of double cantilever beam (DCB) samples, and the subsurface hydrogen concentration rules were obtained by hydrogen permeation test. A hydrogen damage model based on the threshold stress intensity factor of hydrogen-induced cracking arrest was established for X80 pipeline steel. The hydrogen permeation data showed that in 0.5 mol/L H2SO4 + 0.2 g/L CH4N2S solution, the relationship between subsurface hydrogen concentration C-0 and applied current density i satisfied the expression of C-0/L i when the current density was 110 mA/cm(2). The relationship between the threshold stress intensity factor of hydrogen-induced cracking arrest K-HSC and the subsurface hydrogen concentration C-0 satisfied the expression of K-HSC -lnC(0). An analytical model of K-HSC = -0.4648lnC0-1.5040 was proposed for the API X80 steel pipe used in the experimental. The K-HSC value under cathodic interference was calculated according to the C-0 value in the soil simulation solution, and the risk of crack growth was analyzed under service conditions.