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首页> 外文会议>International Conference on Proceeding amp; Manufacturing of Advanced Materials; 20060704-08; Vancouver(CA) >Self-Healing of Creep Cavities by Boron Segregation and Boron Nitride Precipitation Autonomously Developed during High Temperature Use
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Self-Healing of Creep Cavities by Boron Segregation and Boron Nitride Precipitation Autonomously Developed during High Temperature Use

机译：在高温使用过程中自主产生的硼偏析和氮化硼沉淀自动产生的蠕变腔自愈合

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In heat resisting steels, creep cavities are formed at grain boundaries through long time use at high temperatures and stresses. These creep cavities grow along grain boundaries, lead to grain boundary cracks by linking up each other, and cause the low ductility and premature fracture. The long time creep rupture properties of heat resisting steels depend mainly on growth of creep cavities. As creep cavities are thought to grow by diffusive transport of matter from the cavity surface to the grain boundary, a surface control of creep cavities may be very effective for suppression of the creep cavity growth. In this study, the chemical composition of austenitic stainless steels have been modified with the addition of minute amount elements such as boron and cerium with the aim to suppress creep cavitation by segregation of boron and precipitation of boron nitride onto creep cavity surface. Chemistry of creep cavity surface was analyzed by Auger electron spectroscopy. Extensive sulfur segregation was observed on creep cavity surface of the steels without boron and cerium addition. In the modified steels, the segregation of elemental boron and the precipitation of boron nitride compound were observed on the creep cavity surfaces. The segregation and the precipitation were thought to suppress the surface diffusion of creep cavity, since both boron and boron nitride are very stable at high temperatures. Cerium acted as a getter for soluble sulfur in the steels by the precipitation of ceriumoxysulfide (Ce_2O_2S) to facilitate the segregation of boron and precipitation of boron nitride. The segregation of boron and the precipitation of boron nitride reduced creep cavity growth rate substantially, and improved markedly long time creep rupture strength coupled with long time ductility. It may be said that the segregation and the precipitation provide the steels with the self-healing function for cavitation, since they are autonomously developed during the high temperature use.
机译：在耐热钢中，在高温和高应力下长时间使用会在晶界形成蠕变腔。这些蠕变空穴沿着晶界生长，通过相互连接而导致晶界裂纹，并导致低延展性和过​​早断裂。耐热钢的长时间蠕变断裂特性主要取决于蠕变腔的生长。由于蠕变腔被认为是由于物质从腔表面到晶界的扩散传输而生长，因此蠕变腔的表面控制对于抑制蠕变腔的生长可能非常有效。在这项研究中，奥氏体不锈钢的化学成分已通过添加微量元素（例如硼和铈）进行了改性，目的在于抑制由于硼的偏析和氮化硼在蠕变腔表面的析出而引起的蠕变空化。通过俄歇电子能谱分析蠕变腔表面的化学性质。在未添加硼和铈的情况下，在钢的蠕变腔表面观察到大量的硫偏析。在改性钢中，在蠕变腔表面观察到元素硼的偏析和氮化硼化合物的沉淀。由于硼和氮化硼在高温下都非常稳定，因此认为偏析和沉淀抑制了蠕变腔的表面扩散。铈通过硫化铈氧化铈（Ce_2O_2S）的沉淀作用来吸收钢中的可溶性硫，从而促进硼的偏析和氮化硼的沉淀。硼的偏析和氮化硼的沉淀大大降低了蠕变腔的生长速率，并显着提高了长时间的蠕变断裂强度和长时间的延展性。可以说，偏析和析出为钢提供了空化的自愈功能，因为它们是在高温使用过程中自主发展的。

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