氫蝕HTHA和氫脆HE是兩種不同的氫損傷現象，它們在發生條件、機理、可逆性等方面存在明顯區別。

一、發生條件

• 氫蝕：通常在高溫（≥220℃）和高壓氫環境中發生，氫與金屬中的碳化物等組分發生化學反應。
• 氫脆：可在常溫或中溫下發生，氫原子滲透進入金屬內部，與應力共同作用導致材料脆化。

1. 二、機理

   • 氫蝕：氫與金屬中的碳化物（如Fe?C）反應生成甲烷（CH?），甲烷在晶界積聚形成局部高壓，導致晶界裂紋和鼓包。
   • 氫脆：氫原子在晶界、位錯等缺陷處聚集，干擾位錯運動或形成高壓氫氣，降低材料結合力。

2. 三、可逆性

   • 氫蝕：不可逆，一旦發生脫碳和晶界破壞，材料性能無法恢復。
   • 氫脆：部分可逆，通過脫氫處理（如熱處理）可使材料性能恢復，但嚴重時不可逆。
     
   • 四、典型應用場景
   • 氫蝕：常見于石油加氫、合成氨等高溫臨氫設備。
   • 氫脆：多發生于輸氫管道、臨氫零部件，或高強度鋼在含氫環境下的使用。
     
   • 五、材料選擇
   • 氫蝕：需選用含Cr、Mo等元素的抗氫蝕合金（如15CrMo鋼），通過Nelson曲線評估材料適用性。
   • 氫脆：優先選擇低強度鋼或含Ni、Mo的合金鋼，避免使用高強度馬氏體鋼。

六、總結：氫蝕是高溫高壓下的化學反應導致的不可逆損傷，氫脆是常溫下氫與應力協同作用的可逆性脆化。兩者雖都與氫相關，但機理和防控策略差異顯著，需根據具體工況選擇針對性措施。

【擴展閱讀】

以下關于高溫氫蝕的介紹來源于TWI。

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

 什么是高溫氫蝕(HTHA)/熱氫腐蝕？

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.高溫氫蝕（HTHA），也稱為熱氫腐蝕，是在煉油、石化及其他化工設施中，以及可能在高壓蒸汽鍋爐中，鋼材在高溫（通常高于400°F或204°C）氫氣環境下運行時面臨的問題。不應將其與氫脆或其他形式的低溫氫損傷相混淆。

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.高溫氫蝕是由于氫解離并溶解在鋼中，然后與鋼中溶解碳反應生成甲烷所致。這可能導致表面脫碳（當反應主要發生在表面并從材料中吸走碳時）或內部脫碳（當原子氫滲透到材料中并與碳反應生成甲烷，甲烷在晶界和/或沉淀界面處積聚且無法從鋼中擴散出去時）。這會造成高溫氫蝕典型的裂紋和開裂。

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.高溫氫腐蝕是由于氫離解并溶解在鋼中，然后與鋼中的溶解碳反應生成甲烷所致。這可能導致表面脫碳（當反應主要發生在表面并從材料中吸走碳時）或內部脫碳（當原子氫滲透到材料中并與碳反應生成甲烷，甲烷在晶界和/或沉淀界面處積聚且無法從鋼中擴散出去時）。這會造成高溫氫腐蝕典型的裂紋和開裂。

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.影響高溫氫腐蝕的主要因素是氫分壓、鋼的溫度和暴露持續時間。損傷通常在一段潛伏期后發生，潛伏期的長短取決于環境的惡劣程度，可從幾小時到數年不等。高溫和低氫分壓有利于表面脫碳，而相反的條件（較低溫度、高氫分壓）則有利于開裂。此外，鋼的成分會影響其對高溫氫蝕的抵抗力；特別是將碳結合成穩定析出物的元素，如鉻（Cr）、鉬（Mo）和釩（V），非常重要。此類元素含量的增加會提高抗高溫氫蝕能力，含鉻量超過5%的鉻鉬鋼以及奧氏體不銹鋼則不易受高溫氫蝕影響。

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，納爾遜（Nelson）收集并整理了對不同鋼材的多項實驗觀察結果。在納爾遜圖中，溫度/氫分壓圖上標有邊界線，劃定了碳鋼、1.25Cr-0.5Mo鋼等的安全使用區域。該圖已由美國石油學會（API）多次更新，并發表在API推薦做法941中。最近，分析模型已被成功用于預測高溫氫腐蝕的動力學（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.人們越來越擔心，納爾遜曲線可能與高溫氫氣環境中使用的新型鋼材不相關，或者可能過于保守，并且越來越傾向于對熱氫環境中的設備進行基于風險的檢查(RBI)。

來源：

【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/