ABSTRACT

This study aims a systematic experimental investigation using acoustic emission (AE) non-destructive technique for online monitoring of hydrogen assisted cracking (HAC) in modified 9Cr-1Mo steel (P91 steel) welds during Gap-Bead on Plate (G-BOP) and implant tests. Welds made without preheating, with different preheating and combined pre and post heating were tested using G-BOP test. AE results of G-BOP tests have shown that time duration in which HAC active varies with temperature of preheating and combined pre and post heating. Reduction of AE activity in welds made with pre and post heating compared to those only made with preheating revealed a beneficial effect of the former in reducing HAC. In the case of implant tests, crack initiation and propagation are identified for different applied loads from the AE analysis. An attempt has been made to compare HAC during G-BOP tests and implant tests using AE frequency analysis. The dominant frequency of AE signals characteristic of HAC has been identified. This study shows the potential of using AE frequency analysis for online monitoring of hydrogen assisted cracking (HAC) in welds.

摘要

本研究旨在利用声发射 (AE) 无损技术对改性 9Cr-1Mo 钢 (P91 钢) 焊缝中的氢辅助裂纹 (HAC) 进行系统的实验研究，该焊缝在板间隙焊道 (G-BOP) 和植入测试。使用 G-BOP 测试对未预热、不同预热和组合预热和后加热的焊缝进行测试。G-BOP 测试的 AE 结果表明，HAC 活性的持续时间随预热温度和前后加热组合温度而变化。与仅通过预热制成的焊缝相比，通过预热和后加热制成的焊缝中 AE 活性的降低揭示了前者在降低 HAC 方面的有益效果。在植入物测试的情况下，从 AE 分析中识别出针对不同施加载荷的裂纹萌生和扩展。已尝试使用 AE 频率分析比较 G-BOP 测试和植入测试期间的 HAC。已经确定了具有 HAC 特征的 AE 信号的主频。本研究显示了使用 AE 频率分析在线监测焊缝氢辅助裂纹 (HAC) 的潜力。