氢蚀HTHA和氢脆HE是两种不同的氢损伤现象，它们在发生条件、机理、可逆性等方面存在明显区别。

一、发生条件

• 氢蚀：通常在高温（≥220℃）和高压氢环境中发生，氢与金属中的碳化物等组分发生化学反应。
• 氢脆：可在常温或中温下发生，氢原子渗透进入金属内部，与应力共同作用导致材料脆化。

1. 二、机理

   • 氢蚀：氢与金属中的碳化物（如Fe₃C）反应生成甲烷（CH₄），甲烷在晶界积聚形成局部高压，导致晶界裂纹和鼓包。
   • 氢脆：氢原子在晶界、位错等缺陷处聚集，干扰位错运动或形成高压氢气，降低材料结合力。

2. 三、可逆性

   • 氢蚀：不可逆，一旦发生脱碳和晶界破坏，材料性能无法恢复。
   • 氢脆：部分可逆，通过脱氢处理（如热处理）可使材料性能恢复，但严重时不可逆。
     
   • 四、典型应用场景
   • 氢蚀：常见于石油加氢、合成氨等高温临氢设备。
   • 氢脆：多发生于输氢管道、临氢零部件，或高强度钢在含氢环境下的使用。
     
   • 五、材料选择
   • 氢蚀：需选用含Cr、Mo等元素的抗氢蚀合金（如15CrMo钢），通过Nelson曲线评估材料适用性。
   • 氢脆：优先选择低强度钢或含Ni、Mo的合金钢，避免使用高强度马氏体钢。

六、总结：氢蚀是高温高压下的化学反应导致的不可逆损伤，氢脆是常温下氢与应力协同作用的可逆性脆化。两者虽都与氢相关，但机理和防控策略差异显著，需根据具体工况选择针对性措施。

【扩展阅读】

以下关于高温氢蚀的介绍来源于TWI。

What is high temperature hydrogen attack(HTHA)/ hot hydrogen attack?

 什么是高温氢蚀(HTHA)/热氢腐蚀？

High temperature hydrogen attack (HTHA), also called hot hydrogen attack, is a problem which concerns steels operating at elevated temperatures (typically above 400°F or 204°C) in hydrogen environments, in refinery, petrochemical and other chemical facilities and, possibly, high pressure steam boilers. It is not to be confused with hydrogen embrittlement or other forms of low temperature hydrogen damage.高温氢蚀（HTHA），也称为热氢腐蚀，是在炼油、石化及其他化工设施中，以及可能在高压蒸汽锅炉中，钢材在高温（通常高于400°F或204°C）氢气环境下运行时面临的问题。不应将其与氢脆或其他形式的低温氢损伤相混淆。

HTHA is the result of hydrogen dissociating and dissolving in the steel, and then reacting with the carbon in solution in the steel to form methane. This can result in either surface decarburisation, when the reaction mostly occurs at the surface and draws carbon from the material, or internal decarburisation when atomic hydrogen penetrates the material and reacts with carbon to form methane, which accumulates at grain boundaries and/or precipitate interfaces, and cannot diffuse out of the steel. This causes the fissures and cracking which are typical of HTHA.高温氢蚀是由于氢解离并溶解在钢中，然后与钢中溶解碳反应生成甲烷所致。这可能导致表面脱碳（当反应主要发生在表面并从材料中吸走碳时）或内部脱碳（当原子氢渗透到材料中并与碳反应生成甲烷，甲烷在晶界和/或沉淀界面处积聚且无法从钢中扩散出去时）。这会造成高温氢蚀典型的裂纹和开裂。

Surface decarburisation results in a decrease in hardness and increase in ductility of the material near the surface. This is usually only a minor concern for these types of application. However, internal decarburisation, and in particular the formation of methane and consequent development of voids, can lead to substantial deterioration of mechanical properties due to loss of carbides and formation of voids, and catastrophic failure.高温氢腐蚀是由于氢离解并溶解在钢中，然后与钢中的溶解碳反应生成甲烷所致。这可能导致表面脱碳（当反应主要发生在表面并从材料中吸走碳时）或内部脱碳（当原子氢渗透到材料中并与碳反应生成甲烷，甲烷在晶界和/或沉淀界面处积聚且无法从钢中扩散出去时）。这会造成高温氢腐蚀典型的裂纹和开裂。

The main factors influencing HTHA are the hydrogen partial pressure, the temperature of the steel and the duration of the exposure. Damage usually occurs after an incubation period, which can vary from a few hours to many years depending on the severity of the environment. High temperatures and low hydrogen partial pressures favour surface decarburisation while the opposite conditions (lower temperature, high hydrogen partial pressure) favour fissuring. In addition, the composition of the steel influences the resistance to HTHA; in particular elements that tie-up carbon in stable precipitates such as Cr, Mo and V are very important. Increasing content of such elements increases the resistance to HTHA, and Cr-Mo steels with more than 5% Cr, and austenitic stainless steels, are not susceptible to HTHA.影响高温氢腐蚀的主要因素是氢分压、钢的温度和暴露持续时间。损伤通常在一段潜伏期后发生，潜伏期的长短取决于环境的恶劣程度，可从几小时到数年不等。高温和低氢分压有利于表面脱碳，而相反的条件（较低温度、高氢分压）则有利于开裂。此外，钢的成分会影响其对高温氢蚀的抵抗力；特别是将碳结合成稳定析出物的元素，如铬（Cr）、钼（Mo）和钒（V），非常重要。此类元素含量的增加会提高抗高温氢蚀能力，含铬量超过5%的铬钼钢以及奥氏体不锈钢则不易受高温氢蚀影响。

In 1949, Nelson gathered and rationalised a number of experimental observations on different steels. In the Nelson diagram, boundaries are placed in a temperature/hydrogen partial pressure graph, which delineates the region of safe use for carbon steels, 1.25Cr-0.5Mo steels, etc. This diagram has been updated a number of times by the American Petroleum Institute (API) and published in the API recommended practice 941. More recently, analytical models have been used to predict the kinetics of HTHA with some success (Shih, 1982 and Parthasarathy, 1985).1949年，纳尔逊（Nelson）收集并整理了对不同钢材的多项实验观察结果。在纳尔逊图中，温度/氢分压图上标有边界线，划定了碳钢、1.25Cr-0.5Mo钢等的安全使用区域。该图已由美国石油学会（API）多次更新，并发表在API推荐做法941中。最近，分析模型已被成功用于预测高温氢腐蚀的动力学（Shih，1982；Parthasarathy，1985）。

There is increasing concern that the Nelson curves may not be relevant for the newer steels being used in high temperature hydrogen service, or may be overly conservative, and there are increasing trends towards risk-based inspection of items in hot hydrogen service.人们越来越担心，纳尔逊曲线可能与高温氢气环境中使用的新型钢材不相关，或者可能过于保守，并且越来越倾向于对热氢环境中的设备进行基于风险的检查(RBI)。

来源：

【1】https://www.twi-global.com/technical-knowledge/faqs/what-is-high-temperature-hydrogen-attack-htha-hot-hydrogen-attack

【2】https://www.stress.com/services/energy/downstream/solutions/high-temperature-hydrogen-attack-htha-assessments/