阴极极化条件下X80钢及其焊缝的氢渗透行为

 钢中吸收的氢能导致其机械性能损失。采用电化学氢渗透技术,研究了阴极极化条件下X80管线钢及其焊缝在鹰潭土壤环境中氢渗透行为,并利用光学显微镜观察了实验后的试样形貌。结果表明,阴极极化条件下,氢在X80钢中的扩散行为既取决于阴极极化电位,又与显微组织结构有关。随着阴极极化程度增加,氢在X80管线钢中母材和焊缝的可扩散氢浓度和氢陷阱数逐渐增大,氢致开裂敏感性增加。X80钢焊缝氢致开裂敏感性高于母材。阴极极化程度低于-1000mV(SCE)时,母材和焊缝的析氢反应动力学不同。当阴极极化程度高于-1100mV(SCE)时,焊缝内氢压超过其塑性极限,氢鼓泡破裂。母材中氢浓度持续增加,氢鼓泡继续长大。母材中针状铁素体和珠光体对氢扩散的阻碍作用,大于焊缝热影响区粗大的贝氏体和熔合线先共析铁素体。

Hydrogen Permeation Behaviors of X80 Steel and Weld Joint Under Cathodic Polarization

Absorption of hydrogen in steel could lead to the loss of mechanical properties. The electrochemistry hydrogen permeation technology was used to study the hydrogen permeation of the X80 steel base metal and weld joint in Yingtan soil simulation solution under cathodic polarization potentials. The morphologies were observed by optical microscopy after hydrogen permeation experiments. The results show that the behavior of hydrogen diffusion in X80 steel depended on both the cathodic polarization potential and the microstructure. The hydrogen concentration and traps in X80 steel base metal and weld both increased with the cathodic potential moving negatively, which indicated hydrogen induced cracking(HIC) sensitivity increased. The HIC sensitivity of weld joint was higher than that of base metal. The hydrogen evolution reaction kinetics was different between base metal and weld when the cathodic potential was higher than-1000mV(SCE). The hydrogen bubble burst on the weld surface because of hydrogen pressure inside the metal exceeding the plastic limit. However, hydrogen concentration kept increasing in base metal when the cathodic potential reached-1200mV (SCE). The inhibition of acicular ferrite and pearlite on hydrogen diffusion in base meal was greater than coarse bainite in HAZ and proeutectoid ferrite in fusion line.