一般采用气相充氢和电化学充氢两种方式研究氢对金属性能的影响。气相充氢速度相对较慢，氢溶解量低，适合用来研究氢在金属表面的吸附过程。电化学充氢简便易行，且充氢速度较快，氢扩散程度较大，氢溶解量更高，更适合用来研究氢被捕获后对金属性能影响的研究。氢原子进入钢中分为氢在钢表面吸附和在钢中扩散两个过程。由于氢分子很难直接进入钢中，环境中的H2分子在金属(M)表面吸附成为H2M，H2M分解成吸附HM原子才能进入钢中[12]，导致氢脆发生。氢脆分为氢致塑性损伤、氢鼓泡、氢腐蚀和氢致裂纹等几种类型[13]，其敏感性取决于多个因素，包括材料的化学成分、实际服役环境、充氢条件及实验条件等[14]，各因素均会不同程度影响氢浓度和氢扩散速率，其与应力组合导致金属的氢脆或氢致开裂。周成双等[15]探究了晶体缺陷对预充氢X80管线钢氢脆行为的影响，发现位错是预变形过程中氢陷阱的主要来源。刘玉等[16]研究了管线钢在模拟深海环境中的氢脆敏感性，认为氢原子的渗入削弱了钢材内部不同组织间的结合强度，从而导致材料宏观力学性能的降低，与吸附降低表面能理论相符。此外，与母材相比，焊缝组织具有更高的氢捕获能力，更容易形成氢致裂纹[17]。焊缝中夹杂物、位错、析出相等缺陷比母材高。夹杂物的数量、形态、尺寸及分布以及管道钢的组织结构会影响氢的扩散率和捕获率，从而影响氢脆的敏感性[18]。陈旭等[19]采用电化学氢渗透方法探究了阴极保护电位对X80钢母材及其焊缝在鹰潭土壤环境中氢腐蚀行为的影响，结果表明，针状铁素体与珠光体结构对氢的扩散过程具有较为明显的阻碍效果。Shirband等[20]采用电化学渗透方法研究X70管线钢中的氢渗透行为，表明氢扩散系数随晶粒尺寸增加而增加，晶格扩散是主要的氢扩散机制。
本文采用电化学充氢方法对X65钢母材及焊缝进行充氢，通过扫描电镜(SEM)和电化学测试研究了氢对X65钢母材及焊缝腐蚀行为的影响；采用慢应变速率拉伸方法研究了氢对力学性能的影响。研究结果将为我国油气管道氢腐蚀提供理论基础及数据支撑。
1 实验方法
1.1 实验材料
表1 X65管线钢化学成分 (mass fraction / %)
Table 1
| Material | C | Si | Mn | P | S | Cu | Ti | Cr | Al | Ni | V | Nb | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Base metal | 0.11 | 0.28 | 1.38 | 0.015 | 0.028 | 0.02 | 0.02 | 0.02 | 0.06 | 0.02 | 0.06 | 0.04 | Bal. |
| Weld joint | 0.07 | 0.18 | 1.51 | 0.020 | 0.004 | 0.02 | 0.02 | 0.04 | 0.02 | 0.02 | 0.06 | 0.06 | Bal. |
图1
图1
X65管线钢母材及其焊缝金相组织
Fig.1
Microstructure of X65 pipeline steel of base metal (a) and welds (b)
1.2 氢捕获量测量
电化学充氢试样尺寸为10 mm × 10 mm × 2 mm。将铜导线点焊于试样背面，并采用环氧树脂对非工作表面封装，留出1 cm2的工作面积。用水砂纸对试样表面进行梯度机械打磨，并用金刚石抛光膏将样品抛光至镜面。用丙酮和无水乙醇清洗样品后吹干待用。
SEM (SU8010)下观察不同充氢电流密度和充氢时间下X65钢母材和焊缝试样形貌。
1.3 电化学实验
采用电化学方法评价电化学充氢对X65钢母材及焊缝腐蚀行为的影响。电化学实验在Zennium-40555型电化学工作站上完成。采用三电极体系，工作电极为X65钢母材和焊缝，辅助电极为Pt电极，参比电极为饱和甘汞电极(SCE)，实验溶液为3.5% (质量分数) NaCl溶液。电化学充氢条件与氢捕获量测试相同。充氢后静置1 h，待开路电位稳定后进行动电位极化曲线测试。动电位极化曲线测试电位扫描范围-1.2~0.0 V (SCE)，扫描速率为0.667 mV/s。实验在室温下进行。本文所有电位均为相对于饱和甘汞电极。
1.4 慢应变速率拉伸实验
采用慢应变速率拉伸实验(SSRT)研究氢对X65钢母材及焊缝力学性能的影响。SSRT试样尺寸如图2所示。实验前将拉伸试样标距段用水砂纸打磨至2000#，用丙酮去油污，用无水乙醇和去离子水冲洗后吹干。将拉伸试样封装在拉伸盒中，标距段留出5 cm2的暴露面积，对试样进行电化学充氢。充氢条件与氢捕获量测试相同。充氢后立即进行SSRT实验，拉伸速率为1 × 10-6 mm/s。实验在室温下进行。每个充氢电流密度下至少重复2次，以保证数据的可靠性。
图2
试样拉断后，根据
式中，φ为断面收缩率，S0为试件原始横截面，S1为拉伸后断口横截面的面积；δ为延伸率，L0为试件原始标距长度，L1为拉伸后试件的标距长度。
实验后，截取拉伸试样断口，在添加六次甲基四胺的HCl中对断口超声清洗后，采用SEM观察断口形貌。
2 实验结果
2.1 不同充氢电流密度下X65钢氢捕获量
图3为不同充氢电流密度下X65钢母材及其焊缝放氢量随时间变化曲线。可以看出，母材和焊缝表现出相同的趋势，即在开始的6 h内，钢中氢气压力较高，氢气逸出的速度最快。随着时间延长，氢气逸出速率降低，表明钢中滞留氢含量减少。此外，母材和焊缝中氢逸出量随充氢电流密度的增加而增加。相同充氢电流密度下，焊缝中氢逸出量均大于母材，表明焊缝对氢的捕获量大于母材。
图3
图3
不同充氢电流密度下X65钢母材和焊缝氢逸出量
Fig.3
Volume of released hydrogen of X65 steel base metal (a) and welds (b) at different hydrogen charging current densities
图4为不同充氢电流密度下X65钢母材和焊缝充氢16 h后试样表面SEM结果。未充氢时，母材和焊缝试样表面平整(图4a1和a2)。充氢后，随充氢电流密度的增加，母材和焊缝逐渐出现白点和氢鼓泡，且鼓泡的尺寸及数量均增加。充氢电流密度为10 mA/cm2时，母材出现明显的氢鼓泡，且鼓泡边缘出现裂纹(图4b1)，而焊缝试样表面仅有较小的氢鼓泡(图4b2)。当充氢电流密度为25 mA/cm2时，母材表面的氢鼓泡进一步长大(图4c1)，焊缝表面则出现大量的体积稍小的氢鼓泡，且氢鼓泡破裂形成坑状(图4c2)。当充氢电流密度达到50 mA/cm2时，母材表面也出现大量的氢鼓泡和点蚀坑(图4d1)，焊缝氢鼓泡数量增加，鼓泡边缘破裂(图4d2)。这表明，焊缝中能吸收的氢更多，即焊缝比母材对氢的“容忍度”更高。
图4
图4
不同充氢电流密度下X65钢母材及其焊缝充氢后SEM图
Fig.4
SEM images of the base metal (a1-d1) and welds (a2-d2) of X65 steel after hydrogen charging at 0 mA/cm2 (a), 10 mA/cm2 (b), 25 mA/cm2 (c) and 50 mA/cm2 (d) hydrogen charging current densities
2.2 不同充氢电流密度下X65钢SSRT曲线及断口形貌
不同充氢电流密度下X65钢的母材和焊缝的SSRT结果见图5。母材在充氢电流密度为10 mA/cm2时，力学性能没有显著变化，抗拉强度略有提高，应变略有降低。然而当充氢电流密度增加至25 mA/cm2时，应变骤降，强度有明显提高；继续增加电流密度至50 mA/cm2，应变基本没有变化。充氢电流密度为10 mA/cm2时，焊缝力学性能变化与母材基本相同；但充氢电流密度为25 mA/cm2时，焊缝的应变下降程度没有母材大，约为未充氢时的50%；当电流密度达到50 mA/cm2时，应变变化与母材一致。值得注意的是，当充氢电流密度达到25 mA/cm2以上时，焊缝的抗拉强度显著降低。
图5
图5
不同充氢电流密度下X65钢母材及其焊缝应力-应变曲线
Fig.5
Stress-strain curves of X65 steel base metal (a) and welds (b) under different hydrogen charging current densities
图6为不同充氢电流密度下X65钢的母材和焊缝的断面收缩率(Ψ)和延伸率(δ)。可以看出，母材和焊缝的延伸率、断面收缩率均随着充氢电流密度的增大而逐渐减小。充氢电流密度为10 mA/cm2时，母材的Ψ和δ值均大于焊缝。但当充氢电流密度达到25 mA/cm2时，母材的的Ψ和δ值均小于焊缝；当充氢电流密度达到50 mA/cm2时，氢对母材和焊缝的Ψ和δ值影响的几乎没有差异。
图6
图6
不同充氢电流密度下X65 钢母材及焊缝断面收缩率和延伸率
Fig.6
Reduction of area (a) and elongation (b) of X65 steel base metal and welds under different hydrogen charging current densities
通常用氢脆敏感性指数IHE表示金属材料对氢脆的敏感性[23]：
式中，δ0材料未充氢条件下的延伸率；δH材料充氢条件下的延伸率。
图7为不同充氢电流密度下X65钢母材及其焊缝的氢脆敏感性指数IHE计算结果。可以看出，当充氢电流密度为10 mA/cm2时，焊缝的IHE大于母材；但当充氢电流密度达到25 mA/cm2以上时，焊缝的IHE小于母材。由此可见，在钢中氢浓度较高时，氢对母材力学性能的影响大于对焊缝的影响。
图7
图7
不同充氢电流密度下X65钢母材及焊缝的氢脆敏感性指数
Fig.7
IHE of X65 steel base metal and welds at different hydrogen charging current densities
图8为不同充氢电流密度下X65钢母材SSRT实验后主断口形貌。从宏观断口形貌可以观察到，当充氢电流为0和10 mA/cm2时，断口有颈缩现象。微观形貌观察表明，断口为典型的韧窝形貌，与未充氢时(图8a2)相比，充氢电流为10 mA/cm2时(图8b2)，韧窝尺寸和深度韧窝变小变浅，但仍具有明显的韧性断裂特征。随着充氢电流密度的增加至25 mA/cm2，宏观断口形貌颈缩消失(图8c1)，试样表面变得非常不平整，微观形貌中能看到裂纹起源于氢鼓泡(图8c2)，断口呈河流状花样，此时氢脆效应显著。当充氢电流密度为50 mA/cm2时，宏观断口与25 mA/cm2类似(图8d1)，微观断口观察到了解理台阶(图8d2)，韧窝消失，氢脆程度增加。
图8
图8
X65钢母材在不同充氢电流密度下主断口形貌
Fig.8
Fracture morphologies of X65 steel base metal under 0 mA/cm2 (a), 10 mA/cm2 (b), 25 mA/cm2 (c) and 50 mA/cm2 (d) hydrogen charging current densities
图9
图9
X65钢母材在不同充氢电流密度下侧面断口形貌
Fig.9
SEM images of the fracture on side surfaces of X65 steel base metal 0 mA/cm2 (a), 10 mA/cm2 (b), 25 mA/cm2 (c) and 50 mA/cm2 (d) hydrogen charging current densities
图10
图10
X65钢焊缝在不同充氢电流密度下主断口形貌
Fig.10
Fracture morphologies of X65 steel welds under 0 mA/cm2 (a), 10 mA/cm2 (b), 25 mA/cm2 (c) and 50 mA/cm2 (d) hydrogen charging current densities
图11
图11
X65钢焊缝在不同充氢电流密度下侧面断口形貌
Fig.11
SEM images of the fracture on side surfaces of X65 steel welds under 0 mA/cm2 (a), 10 mA/cm2 (b), 25 mA/cm2 (c) and 50 mA/cm2 (d) hydrogen charging current densities
2.3 不同充氢电流密度下X65钢极化曲线
图12为不同充氢电流密度下X65钢母材及其焊缝在3.5%NaCl溶液中的极化曲线。母材随充氢电流密度增加，自腐蚀电位下降，表明充氢降低了母材耐蚀性。充氢后焊缝自腐蚀电位变化趋势与母材一致，但下降幅度较小。母材在充氢电流密度为50 mA/cm2时出现了明显的钝化现象。焊缝在充氢电流密度为25和50 mA/cm2时出现钝化现象，但钝化区间比母材小。不同充氢电流密度下母材的阴极极化曲线几乎重合，表明充氢对母材阴极极化行为影响较小。此外，焊缝的阳极极化曲线斜率明显低于母材，且充氢电流密度对焊缝阳极极化曲线影响较小。采用Tafel外推法对极化曲线进行拟合，得到腐蚀电流密度Icorr结果见图13。可以看出，未充氢时，X65钢母材和焊缝Icorr基本相同。充氢后，随充氢电流密度增加，母材和焊缝腐蚀电流密度均增大，且焊缝的腐蚀电流密度大于母材。
图12
图12
不同充氢电流密度下X65钢母材及其焊缝的极化曲线
Fig.12
Polarization curves of X65 steel base metal (a) and welds (b) under different hydrogen charging current densities
图13
图13
不同充氢电流密度下X65钢母材及其焊缝腐蚀电流密度
Fig.13
Corrosion current density of X65 steel base metal and welds under different hydrogen char-ging current densities
3 分析及讨论
3.1 X65钢母材及焊缝显微组织对氢捕获量的影响
氢逸出量测试结果表明，随着充氢电流密度增加，X65钢母材及焊缝氢逸出量均呈现递增趋势，表明材料内部氢捕获量随充氢电流密度增加而增多。在充氢过程中，充氢电解液中的H＋在阴极反应中获得电子还原为氢原子并吸附于钢表面，形成表面氢浓度梯度。随着充氢电流密度增大，试样表面氢浓度升高，化学位梯度增大，促进氢原子向材料内部扩散渗透[23]。但随着充氢电流密度超过一定阈值后，氢捕获量增加程度逐渐下降，表明母材和焊缝试样内部氢陷阱容量存在上限。相同充氢条件下，焊缝氢逸出量显著高于母材，表明焊缝氢捕获能力更强。这与母材与焊缝显微组织结构差异密切相关。金相分析结果显示，焊缝组织比母材更为粗大，且具有更高的晶体缺陷密度和位错密度，从而形成更高密度的氢陷阱点位[24]。扩散进入基体的H易在这些氢陷阱处发生富集，导致相同充氢条件下焊缝氢捕获量显著增加[25]。Shirband等[20]采用电化学渗透方法研究X70钢的氢渗透行为，证明了退火处理增加晶粒尺寸，导致氢扩散系数增加。王佳等[25]利用热模拟技术研究了X80钢在不同峰值温度下的焊接热影响氢脆行为，结果表明，相变区的氢脆敏感性最高，从而可能引发氢脆等问题。
SEM结果表明，充氢后母材和焊缝均出现不同程度的氢鼓泡。随着充氢电流密度增加，母材和焊缝表面形成氢鼓泡数量增多。H进入钢体后，在钢中缺陷、位错处聚集，形成H2，破坏X65钢的组织结构。当充氢电流密度小于25 mA/cm2时，母材表面出现明显氢鼓泡，而焊缝表面则未出现，即焊缝鼓泡形成较母材晚，这进一步证明氢陷阱对扩散氢有良好的钉扎作用，阻碍H原子在基体中的扩散。当充氢电流密度达到50 mA/cm2时，焊缝的氢鼓泡数量与体积明显大于母材，且鼓泡破裂，这是由于随可扩散氢量增加，焊缝的氢陷阱内大量聚集形成H2，产生氢内压，当其氢压达到破裂的门槛应力时就导致氢鼓泡破裂[26]。由于焊缝的氢捕获量更大，氢内压更高，因此形成的氢鼓泡比母材更大。
3.2 氢对X65钢母材和焊缝力学性能的影响
SSRT结果表明，充氢后X65钢母材的抗拉强度略有升高。当充氢电流密度为10 mA/cm2时，母材的延伸率略有降低；但当电流密度达到25 mA/cm2时，延伸率显著降低，继续增大电流至50 mA/cm2时，延伸率几乎没有变化。这表明当充氢电流为25 mA/cm2时，钢中氢捕获量达到临界值，诱发显著的氢脆效应。充氢后焊缝力学性能响应与母材存在显著差异：在充氢电流密度为10 mA/cm2时，焊缝的延伸率下降程度大于母材；当充氢电流密度进一步增加至25 A/cm2和50 A/cm2时，焊缝的延伸率未出现母材那样的急剧下降，而是呈现出逐步降低，同时抗拉强度亦有所下降。这归因于焊缝组织具有较高的氢捕获能力，捕获的氢原子在钢中富集引发晶格畸变，并对位错产生钉扎效应，增加位错运动的阻力，使位错运动更加困难，提升了焊缝的抗塑性变形能力[27~29]。
断口形貌SEM结果表明，随着充氢电流密度升高，X65钢母材和焊缝断裂机制呈现出由韧性断裂向脆性断裂转变的趋势。未充氢状态下，试样内部晶粒在拉应力的作用下发生拉长塑性变形，形成典型的等轴韧窝形貌。充氢后，氢原子渗入钢基体内部，并在微裂纹及夹杂物周围发生富集[30]。当局部氢浓度达到临界阈值时，会显著降低原子间的内聚能[31]。当外加载荷产生的应力值超过原子内聚强度阈值时，将诱发微裂纹形核。在充氢电流密度为10 mA/cm2的条件下，扩散至试样芯部的氢原子数量有限，不足以改变材料的断裂模式，故断口芯部仍以韧窝形貌为主导。当充氢电流密度超过25 mA/cm2后，试样断口形貌由韧窝特征逐渐向准解理断裂特征过渡。氢的存在弱化了原子间结合强度，最终引发脆性断裂。Liu等[32]认为，在应力作用下，氢通过促进局部塑性变形机制发挥作用：氢原子在位错附近可削弱位错与障碍物之间的应力场强度，降低位错运动的激活能，使位错在较低能量下发生迁移，进而在断口解理面上形成台阶状滑移线，加速裂纹的扩展并促进解理面的形成。
3.3 氢对X65钢母材和焊缝电化学行为的影响
极化曲线结果表明，电化学充氢在一定程度上促进了母材和焊缝阳极溶解过程。氢可增强体系的活化因子(具体表现为Icorr增加)，提升钢材的电化学活性，导致其耐蚀性下降[33]。充氢后，氢在钢基体中的扩散导致晶界处晶格畸变能升高，使材料表面活性增加、电极电位降低。在与腐蚀介质反应时，晶格畸变能释放所产生应力会加速金属的腐蚀进程。同时，氢原子通过对位错的激活作用，促使钢中微小位错重叠与融合，进一步加速位错的发射与迁移，增加基体的晶体缺陷密度，导致钢在腐蚀介质环境中更容易发生阳极溶解而遭受腐蚀[34]。因此，随充氢程度增加，母材和焊缝阳极溶解程度均增加。此外，电化学结果表明，相同条件下焊缝腐蚀电流密度大于母材。这是由于焊缝捕获了更多的氢所致。母材在充氢电流密度达到50 mA/cm2、焊缝在充氢电流密度为25和50 mA/cm2时，阳极极化曲线均出现“钝化”现象，即阳极氧化对腐蚀电流影响较小。这归因于金属表面吸附的氢被氧化消耗了阳极电流。焊缝的钝化区间小于母材，表明在较高的充氢电流密度下，母材表面的氢浓度比焊缝高，而焊缝中由于氢陷阱数大于母材使表面氢浓度降低。这与氢脆敏感系数结果一致。
4 结论
(1) X65钢焊缝比母材具有更高的晶体缺陷密度和位错密度，形成更高密度的氢陷阱点位，相同充氢条件下焊缝的氢捕获量大于母材。
(2) 充氢电流密度为10 A/cm2时，焊缝的氢脆敏感性大于母材；当充氢电流密度达到25 A/cm2以上时，母材的氢脆敏感性反超焊缝。氢陷阱对扩散氢有良好的钉扎作用，阻碍氢原子在基体中的扩散，因此焊缝中较高的氢捕获量使其抗塑性变形能力大于母材。
(3) 氢在钢中的扩散导致晶界处晶格畸变能升高，使材料表面活性增加、电极电位降低，耐蚀性下降。焊缝中氢含量高，增加了晶体缺陷密度高，导致其耐蚀性小于母材。
参考文献
Development situation and consideration of hydrogen energy industry in China
[J].
我国氢能产业发展现状与思考
[J].
我国以化石能源为消费主体，为加快实现"双碳"减排目标，发展清洁能源刻不容缓。从制氢、燃料电池、氢能汽车、加氢站和氢能冶金等方面对我国氢能发展现状进行梳理，分析了我国氢能产业的不足，并对未来氢能发展方向提出建议。研究表明，我国氢能产业处于初级发展阶段，尚未完全掌握氢能核心技术，关键材料及零部件仍依赖进口，导致氢能产业链的生产成本较高。未来我国应加强氢能顶层规划布局、氢能产业核心技术攻关、开展高效制氢技术及拓宽氢能应用场景，为未来氢能大规模发展打下坚实基础。
Adaptability of typical seamless tube steels to hydrogen-blended natural gas environments and hydrogen-induced damage mechanism
[J].
典型无缝钢管钢掺氢天然气环境适应性及氢致损伤机理
[J].针对常用中低强度无缝钢管钢掺氢输送天然气环境适应性问题，本文系统研究了不同掺氢比例体积分数分别为0%、5%、10%、15%、20%和100%对10 MPa天然气环境下钢管钢氢脆(HE)敏感性影响规律及机理。结果表明，低强度L245、X42钢在低掺氢比例环境(≤ 10%)中能保持良好塑性，高掺氢比例环境中(≥ 20%)，延伸率降低，HE敏感性增加；中强度X52钢的HE敏感性维持在较高水平。断口观察表明，低掺氢比例环境中L245与X42钢断口韧性断裂明显，X52钢则已出现部分脆性特征，HE主要由氢增强局部塑性(HELP)机制驱动，同时伴有氢加速应变诱导空位(HESIV)机制；高掺氢比例中，3种钢都表现为由HELP和氢致解理(HEDE)混合机制驱动的脆性断裂特征。综合考虑认为，低于10%的掺氢比例对于上述3种无缝钢管钢是一个相对安全的服役配比。
Review, challenges and suggestions for China's hydrogen energy development in the context of "dual carbon" strategy
[J].
“双碳”背景下中国氢能发展回顾、面临挑战及建议
[J].
Hydrogen damage of X80 pipeline steel in hydrogen-doped gaseous atmosphere
[J].
掺氢环境下X80管线钢气相氢损伤研究
[J].以X80管线钢为研究对象，开展气相氢原位慢速率拉伸实验、气相氢渗透实验和氢含量测试，考察了在温度为298 K时不同掺氢比对X80钢力学行为、氢渗透行为和氢含量的影响，以及在掺氢比为10%条件下温度对气相氢渗透动力学参数的影响。随着掺氢比的增加，X80管线钢的屈服强度和抗拉强度均略微下降，断后延伸率逐渐降低、氢脆敏感指数增大、氢含量增大、氢渗透系数和扩散系数增大。在掺氢比为10%条件下随着温度的上升，氢渗透系数和扩散系数均增大，当温度在298 K至373 K范围内时，X80管线钢的氢扩散激活能和渗透激活能分别为1.56和11.25 kJ/mol。
Effect of hydrogen diffusion model on hydrogen concentration calculation around a crack tip in hydrogen-exposed structures
[J].
氢扩散模型对临氢结构裂尖氢浓度计算影响
[J].
Study on the characteristics of hydrogen-mixed gas in large-diameter long-distance natural gas pipeline
[J].
大口径长输天然气管道掺氢混气特性研究
[J].
Preparation and properties of Co9S8/C materials by coprecipitation method
[J].
共沉淀法制备Co9S8/C材料以及性能研究
[J].
Effect of swirl number on the premixed flame blowout performance of the low calorific value gas not containing hydrogen
[J].
旋流数对不含氢气的低热值燃气预混熄火特性的影响
[J].
A critical review of the influence of hydrogen on the mechanical properties of medium-strength steels
[J].
Hydrogen related degradation in pipeline steel: A review
[J].
Review and assessment of the effect of hydrogen gas pressure on the embrittlement of steels in gaseous hydrogen environment
[J].
Estimation of the influence of compressed hydrogen on the mechanical properties of pipeline steels
[J].Consideration of the possibility of transporting compressed hydrogen through existing gas pipelines leads to the need to study the regularities of the effect of hydrogen on the mechanical properties of steels in relation to the conditions of their operation in pipelines (operating pressure range, stress state of the pipe metal, etc.). This article provides an overview of the types of influence of hydrogen on the mechanical properties of steels, including those used for the manufacture of pipelines. The effect of elastic and plastic deformations on the intensity of hydrogen saturation of steels and changes in their strength and plastic deformations is analyzed. An assessment of the potential losses of transported hydrogen through the pipeline wall as a result of diffusion has been made. The main issues that need to be solved for the development of a scientifically grounded conclusion on the possibility of using existing gas pipelines for the transportation of compressed hydrogen are outlined.
Essence and gap analysis for hydrogen embrittlement of pipelines in high-pressure hydrogen environments
[J].
高压氢气管道氢脆问题明晰
[J].
Effect of microstructure on the mechanical properties and fracture toughness of API X65 pipeline steel in the presence of hydrogen
[J].This study investigated the influence of microstructure on the mechanical properties and fracture toughness of API X65 pipeline steel in the presence of hydrogen. In this study, electrochemical method was used for hydrogen charging and indentation technique was applied to obtain the fracture toughness. The results showed that in the presence of hydrogen, elongation (EL%), reduction of area (RA), ductile fracture percentage, and fracture toughness of all microstructures decreased. The microstructure of martensite (M) + bainite (B) + ferrite (F), had the highest hydrogen trapping and uptake (C-app) as 8.58 x 10(-6) mol cm(-3) and the lowest apparent hydrogen diffusivity (D-app) as 5.68 x 10(-10) m(2) s(-1); thus, the maximum decrements of 33% in fracture toughness, 40% in ductile fracture percentage, 47% in RA, and 35% in EL% were observed. However, the microstructure of ferrite (F) + degenerated perlite (DP) + martensite-austenite micro constituent (M/A), where the lowest value of 5.85 x 10(-6) mol cm(-3) for C-app and the highest value of 8.5 x 10(-10) m(2) s(-1) for D-app had the minimum decrements as 2% in fracture toughness, 10% in ductile fracture percentage, 4% in RA, and 7% in El%. According to the obtained results, depending on the type of microstructures, hydrogen-induced work softening or hardening were observed by decreasing or increasing the yield stress respectively. Graphic
Effect of dislocation on hydrogen embrittlement behavior of X80 pipeline steel
[J].
晶体缺陷对X80管线钢氢脆行为的影响
[J].
Effect of cathodic polarization on hydrogen embrittlement susceptibility of X80 pipeline steel in simulated deep sea environment
[J].<p>Pipeline steels utilized in deep seawater are usually protected cathodically. However, inappropriate operations of cathodic protection systems cause hydrogen embrittlement failures to these high strength steels in seawater which result from the application of excessive negative potentials, leading to massive generation of hydrogen at the protected pipelines' surface. With high strength steels increasingly widely used in the deep sea environment, the basic research to the cathodic protection and susceptibility to hydrogen embrittlement of high strength steels under such a circumstance is still unfortunately relatively lack and urgently needed to supplement. Electrochemical measurement, hydrogen permeation current detection, slow strain rate tensile test (SSRT) and fracture morphology analysis, therefore, were employed to investigate effect of cathodic polarization level on the susceptibility of API X80 pipeline steels to hydrogen embrittlement in simulated deep seawater in the present work. The results showed that the applied cathodic polarization potentials significantly affected hydrogen permeation and hydrogen--induced cracking behavior of X80 steels immersed in deep seawater. A linear relationship was found between the hydrogen permeation current densities and cathodic polarization potentials applied according to the findings of the potential dynamic polarization and hydrogen permeation current measurements. SSRT tests suggested that X80 pipeline steels immersed in simulated deep seawater didn't show susceptibility to hydrogen embrittlement at open circuit potential, and thus the optimum cathodic protection potential range was supposed to be above －900 mV (<em>vs</em> saturated calomel electrode). Under such a cathodic polarization potential, the hydrogen permeation current densities of X80 pipeline steel specimens were less than 0.1157 <em>μ</em>A/cm<sup>2</sup> andtheir mechanical properties didn't decrease remarkably. Once the cathodic polarization potentials lower than －900 mV, however, hydrogen permeation current densities and calculated hydrogen embrittlement coefficients <em>ψ</em> of X80 pipeline steels increased significantly, exhibiting higher susceptibility to hydrogen embrittlement in simulated deep seawater. Furthermore, macro－and micro－morphologies of fracture surface of X80 pipeline steels after SSRT test indicated that the fracture morphology transformed from a dimpled pattern with ductile fracture to a quasi—cleavage pattern when cathodically polarized to lower than －900 mV, <em>i.e.</em> showing obvious brittle failure characteristics.</p>
阴极极化对X80管线钢在模拟深海条件下氢脆敏感性的影响
[J].
Mechanical properties and notch sensitivities of the hydrogenated X70 pipeline steel welded joints
[J].
渗氢X70管线钢焊接接头的力学性能及缺口敏感性
[J].
Hydrogen diffusion and hydrogen influenced critical stress intensity in an API X70 pipeline steel welded joint-experiments and FE simulations
[J].
Hydrogen permeation behaviors of X80 steel and weld joint under cathodic polarization
[J].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.
阴极极化条件下X80钢及其焊缝的氢渗透行为
[J].
Investigating the effect of heat treatment on hydrogen permeation behavior of API X-70 steel
[J].
Effect of hydrogen charging current density on hydrogen embrittlement sensitivity of DH36 steel
[J].
充氢电流密度对DH36钢氢脆敏感性的影响
[J].
Hydrogen induced cracking behaviors of X70 pipeline steel and its welds under electrochemical charging
[J].
电化学充氢条件下X70管线钢及其焊缝的氢致开裂行为
[J].采用电化学充氢的方法研究了X70管线钢在不同浓度硫酸溶液中的氢致开裂(HIC)行为. 结果表明, 增大充氢电流密度、延长充氢时间以及降低充氢溶液的pH值能够促进氢进入X70钢基体. 微观观察表明, X70钢中的非金属夹杂物如氮化物和氧化物等对其氢致开裂行为有不同的影响, 氮化物夹杂并不是充氢裂纹的必然形核位置, 而Mg, Al, Ca等的氧化物是更为有害的氢致裂纹源. 通过氢渗透实验测得室温下氢在X70钢中的有效扩散系数为3.34×10-9cm2/s.对X70管线钢基体及焊缝试样电化学预充氢后拉伸, 焊缝试样的拉伸塑性较差, 各项塑性指标在充氢前、后均低于X70钢基体材料.
Electrochemical hydrogen charging behaviors of high strength pipeline steels
[J].
高强度管线钢电化学充氢行为
[J].
Effect of microstructure on the hydrogen trapping efficiency and hydrogen induced cracking of linepipe steel
[J].
Study on microstructure and hydrogen permeation behavior of welding heat affected zone of X80 pipeline steel
[J].
X80管线钢焊接热影响区组织和氢渗透行为研究
[J].
Influence of cell segregation inclusion of alloying elements on initiation of hydrogen blistering in heat-affected zone of acicular ferrite steels
[J].
合金元素偏聚夹杂对针状铁素体管线钢焊接热影响区氢鼓泡的影响
[J].
Tensile properties evolution of hydrogen-induced TA10 titanium alloy welded joints
[J].
氢致TA10钛合金焊接接头拉伸性能演变
[J].钛合金焊接件低氢浓度下常发生氢脆失效，文中研究了充氢量对钛合金焊接接头拉伸性能的影响规律及其作用机制. 结果表明，随充氢量增加，室温强度明显提升，而塑性指标显著恶化. 充氢0.05% (质量分数)时，固溶氢对组织强化效果有限，抗拉强度略有增加；固溶氢降低了溶质原子对位错运动“钉扎”作用，屈服强度下降；固溶氢仅依靠扩散聚集，致局部微区氢浓度增加，其对塑性影响不大. 充氢0.12%后，氢化物“钉扎”作用加强，氢致位错交叉滑移更为困难，室温强度显著增加；脆性氢化物自身断裂、析出特征或加速与基体分离，致塑性显著下降. 未充氢或0.05% H时，焊接接头发生韧性断裂；充氢0.12%后，以脆性断裂为主；固溶氢、氢化物对断裂方式转变产生直接影响.
The role of hydrogen in hardening/softening steel: Influence of the charging process
[J].
Hydrogen embrittlement in ferritic steels
[J].
Hydrogen diffusion and trapping in X70 pipeline steel
[J].
A review on hydrogen embrittlement of Fe-Al intermetallics
[J].
Fe-Al金属间化合物氢脆效应研究现状
[J].
Hydrogen embrittlement of notched X80 steel under high-pressure gaseous hydrogen: Insights from hollow specimen testing and finite element analysis
[J].
Effect of hydrogen on electrochemical behavior of alloy 600 in high temperature and high pressure water
[J].
氢对600合金在高温高压水中电化学行为的影响
[J].
