力-电耦合影响与近表面环境-组织协同作用下的X80钢氢损伤机制

In recent years, failure risks attributed to Hydrogen Induced Cracking under the co-effects of complex soil stress field and strong electric interference from High Voltage Direct Current (HVDC) transmission and High Speed Rail has been recognized, which increases the safety risk of materials and structures during oil and gas exploitation and transportation. Using and design of high strength pipeline under cathodic protection and different mechanical status safely and reasonably become a new challenge to researcher. This project will focus on the kinetics of hydrogen atoms absorption on the X80 pipeline steel surface and hydrogen atoms adsorption and uptake by metal under the combined environment of stress field and cathodic protection potential. High pressure autoclaves for simulating of subsea pressure, high pressure slow strain rate tensile test, high pressure electrochemical measurement and hydrogen permeation test using high pressure electrode probes will be utilized to investigate the environmental effects of high hydraulic pressure, low temperature, water flow and other physical or chemical factors in deep water subsea and the electrochemical effects of the cathodic polarization induced by cathodic protection and HVDC interference system. Based on the research on the rule and influencing factors of hydrogen permeation under coupling conditions, hydrogen atoms uptake from absorption to adsorption and the hydrogen permeation from surface to bulk, the mechanism of hydrogen kinetics under coupling fields of cathodic potential and mechanical status can be drawn.

大规模建设的长距离油气管线在特高压直流输电线路及高铁造成的电场干扰和复杂地质和结构载荷共同作用下存在氢致损伤甚至开裂风险，给我国能源开发过程中的材料和结构安全带来极大隐患，也给X80以上级别的高强管线钢的安全使用提出新的挑战。本课题针对诱发这类氢致损伤的强干扰电场和复杂应力场耦合环境下的氢渗透过程和X80钢近表面环境与微观组织协同作用下氢扩散-累积动力学行为与氢损伤形成发展机制开展研究，利用多场环境模拟、带复杂载荷加载和电场干扰的氢渗透和电化学测试、带高压环境舱的疲劳和慢应变拉伸等试验方法，研究复杂力学载荷状态和强电场干扰及阴极电化学极化等耦合环境中，氢原子在材料近表面环境与亚表面微观组织结构协同影响下，进入X80钢的动力学过程及其造成的各类氢损伤形式与主要机制，揭示电学和断裂力学参量与氢渗透微观过程的相关性，为建立服役环境下高钢级管线的氢脆评价方法和失效控制边界条件提供理论支撑。

大规模建设的长距离油气管线在特高压直流输电线路及高铁造成的电场干扰和复杂地质和结构载荷共同作用下存在氢致损伤甚至开裂风险，给我国能源开发过程中的材料和结构安全带来极大隐患，也给X80以上级别的高强管线钢的安全使用提出新的挑战。课题针对诱发这类氢致损伤的强干扰电场和复杂应力场耦合环境下的氢渗透过程和X80钢近表面环境与微观组织协同作用下氢扩散-累积动力学行为与氢损伤形成发展机制开展研究，利用多场环境模拟、带复杂载荷加载和电场干扰的氢渗透和电化学测试、带环境舱的疲劳和慢应变拉伸等试验方法，研究复杂力学载荷状态和强电场干扰及阴极电化学极化等耦合环境中，氢原子在材料近表面环境与亚表面微观组织结构协同影响下，进入X80钢的动力学过程及其造成的各类氢损伤形式与主要机制，揭示了电场和断裂力学参量与氢渗透微观过程的相关性，为建立服役环境下高钢级管线的氢脆评价方法和失效控制边界条件提供理论支撑。研究结果表明，强阴极干扰条件下X80钢表面形成的钙质沉积层随阴极电流密度变化，影响了氢吸附、脱附和复合动力学过程，进而提出了X80钢在强阴极电场干扰下的亚表面氢浓度上限值和诱发X80钢氢致裂纹形核的氢浓度门槛值。阐明了电场-应力场耦合条件下的氢渗透动力学规律，基于应力诱导氢扩散影响下的亚表面氢浓度与裂尖氢分布的关系，，提出了氢致裂纹止裂门槛应力强度因子与亚表面氢浓度的计算模型，建立了X80钢氢环境断裂韧性的表征方式。阐明了M/A组元、大角度晶界等显微组织特征对X80钢管材氢脆敏感性的影响机制，提出了X80钢管道及环焊缝在强阴极干扰下裂纹型缺陷氢致扩展的工程临界评估准则。研究成果通过多篇论文发表，明确了X80钢管道在强阴极干扰条件下的氢脆敏感性规律和机制，为高钢级管线钢的研发、工程应用和服役安全提供了理论和实验支撑。