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

Abstract

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 C0 and applied current density i satisfied the expression of C0/L∝ i when the current density was 1–10 mA/cm2. The relationship between the threshold stress intensity factor of hydrogen-induced cracking arrest KHSC and the subsurface hydrogen concentration C0 satisfied the expression of KHSC ∝ -lnC0. An analytical model of KHSC = -0.4648lnC0-1.5040 was proposed for the API X80 steel pipe used in the experimental. The KHSC value under cathodic interference was calculated according to the C0 value in the soil simulation solution, and the risk of crack growth was analyzed under service conditions.