过热器管爆管原因的失效分析

通过金相、扫描电镜、能谱等分析手段，确定本次爆管裂纹起源于内壁，有别于文献中所述长期过热引起的爆管开始于外壁。内外壁的温差应力导致了内表面裂纹的产生。温差应力、蒸汽压力以及烟气温度波动等产生的热冲击使得裂纹从内壁向外壁扩展。当裂纹扩展到一定厚度，氧化层和裂纹深度的叠加导致爆管处受到较高的周向应力，在高应力下产生蠕变疲劳断裂。爆管断口呈脆性特征，也说明不是瞬时过载断裂的，还经历过一个缓慢的疲劳过程。

Failure Analysis of Overheater Tube Booster

This paper confirms this booster of crackle is originated from the inboard wall through metallography, scanning electric mirror, energy spectrum etc. , which is different from the literature stated that long - term overheated booster begins with the exterior wall. The temperature difference stresses of the internal and external walls have caused the crackle of inner surface. Thermal shock from temperature difference stress, vapour pressure and the fluctuation of exhaust gas makes crackle of inside wall expanding from outside one. As the crackle is expanded to certain thickness, oxide layer and crackle depth cause the booster receiving higher hoop stress, which makes creep fatigue rupture under high stress. The fracture of the booster presents the fragility characteristic, also proves it is not the instantaneous overload that makes such rupture, and still experiences a slow tired process.