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首页> 外文期刊>Welding in the World: Journal of the International Institute of Welding: Journal of the International Institute of Welding >Damage assessment of creep affected weldments of a Grade 91 header component after long-term high temperature service
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Damage assessment of creep affected weldments of a Grade 91 header component after long-term high temperature service

机译：长期高温使用后91级联管箱部件的蠕变影响焊件的损伤评估

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摘要

Martensitic Grade 91 heat-resistant steel has been used successfully within power plant construction over the last decades. In this paper, results of a service failure investigation conducted on two parts cut from a creep-damaged header component are presented. After an operational time of about 78,000 h, first cracks, located near the weld toe at the flanks of several stubs, were found in 2006. After repair work, consisting of eliminating the cracks by grinding followed by magnetic particle inspection, the header component went into service for another 9,000 h with unfilled excavations until its replacement. The examinations show typical problems of 9-12 % Cr steels correlating with the Type IV mechanism like extensive pore and cavity formation in the area of the fine-grained heat-affected zone. The state of damage of the welds as well as the adjacent materials-and what this implies for a temporary extended operation of a damaged component-was investigated using hardness measurements, light optical (LOM) and scanning electron microscopy (SEM). It is shown that a repair by open defect-removal excavations eliminates the cracks found within the creep damaged material but implies varied stress conditions in adjacent areas which might favour accelerated creep failure during further operation. Further, the location, size and density of creep cavities were analysed. Microscopic investigations indicate that the main damage has accumulated in an equiaxed grain structure showing significantly smaller grain sizes, which is also shown by electron back scatter diffraction (EBSD) analysis.
机译：在过去的几十年中，马氏体91级耐热钢已在电厂建设中成功使用。在本文中，介绍了从蠕变损坏的割台组件切下的两个零件上进行的服务故障调查的结果。经过约78,000小时的运行时间，2006年在多个短管侧面的焊趾附近发现了第一处裂纹。修理工作包括通过研磨消除裂纹，然后进行磁粉检查，从而使集管组件消失了。在没有填充的情况下，可再使用9,000小时，直到更换为止。检验显示出9-12％Cr钢的典型问题与IV型机理有关，例如在细晶粒热影响区的区域中形成大量的孔和腔。使用硬度测量，光学光学（LOM）和扫描电子显微镜（SEM）研究了焊缝及相邻材料的损坏状态，以及这对损坏的组件进行临时扩展的含义。结果表明，通过开放的缺陷清除开挖进行的修复可以消除在蠕变损坏的材料中发现的裂缝，但是却意味着相邻区域的应力状况会发生变化，这可能会在进一步操作中加速蠕变破坏。此外，分析了蠕变腔的位置，大小和密度。微观研究表明，主要损害已累积在等轴晶粒结构中，显示出明显较小的晶粒尺寸，这也由电子背散射衍射（EBSD）分析表明。

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