HP-Nb合金转化炉管服役过程中的损伤规律

Damage law of HP-Nb alloy reformer tube in service process

对HP-Nb合金转化炉管服役时的显微组织损伤和力学性能衰退规律进行研究。采用光学显微镜、X射线衍射仪分析了不同服役时间下转化炉管显微组织演变和氧化损伤,同时对其常温力学性能、高温蠕变性能、高温抗松弛性能进行了研究。结果表明:长时间的高温服役使HP-Nb合金炉管的一次碳化物粗化,在晶界形成了连续的网状结构;在晶内也析出了大量的二次碳化物,并且随服役时间的延长而长大;初始碳化物由M_(7)C_(3)型碳化物转变为M_(23)C_(6)型碳化物;HP-Nb合金服役过程中发生了内氧化,在炉管内、外表面形成了氧化膜和氧化膜下的贫Cr区;长时间服役后炉管的室温抗拉强度、塑性和韧性、高温蠕变性能、高温抗松弛性能均明显降低。

The microstructure damage and mechanical properties degradation of HP-Nb alloy reformer tubes during service were studied.The microstructure evolution and oxidation damage of reformer tubes with different service time were analyzed by optical microscope and X-ray diffractometer.At the same time,its mechanical properties at room temperature,high temperature creep properties and high temperature relaxation resistance were studied.The results show that the primary carbides of HP-Nb alloy furnace tubes were coarsened by long-term high temperature service,and a continuous network structure was formed at the grain boundary.A large number of secondary carbides were also precipitated in the crystal,and grow with the extension of service time.The initial carbide was transformed from M_(7)C_(3) carbide to M_(23)C_(6) carbide.Internal oxidation occurred during the service of HPNb alloy,and the oxide film and Cr-depleted zone under the oxide film were formed on the inner and outer surfaces of the furnace tube.After long-term service,the room temperature tensile strength,plasticity and toughness,high temperature creep performance and high temperature relaxation resistance of the furnace tube were significantly reduced.