HPM乙烯裂解炉管的渗碳损伤研究

Study on Carburizing Damage of HPM Ethylene Cracking Furnace Tube

利用SEM、XRD、EMPA及金相显微分析等方法对服役五年多的乙烯裂解炉管进行了渗碳损伤研究。结果表明:炉管均有不同程度的渗碳现象,最严重的整个截面已经渗透。炉管的渗碳区域碳化物数量明显增加,形态也由细小的粒状变为粗大的块状,晶界碳化物变为链状。渗碳区域为M23C6和M7C3两种碳化物共存,而非渗碳区域仅存在M23C6型碳化物。Cr和C元素主要以碳化物形式存在,集中在晶界和晶内,而Ni元素仍固溶在奥氏体晶内。炉管内外表面均有氧化损伤层,损伤层内Cr元素主要以氧化物形式分布在晶界。渗碳炉管的热疲劳性能及常温力学性能明显下降,冲击断口为典型的解理断裂。

Through adopting scanning electron microscope（ SEM）,X-ray diffraction（ XRD）,electron probe microanalysis（ EPMA） and other analytical methods,the carburizing damage of 5-year HPM ethylene cracking furnace tube was studied to show that the damage at different levels exists to the extent of nearly permeating the tube thickness,and the carbides can be found increased there obviously,including the fine or massive particles and chain-typed carbides located in the grain boundary. In the carburizing zone,the carbides exist in the form of M23C6 and M7C3and only M23C6 can be found in the zone without carburizing; as for Cr and C elements in the form of carbides,they concentrate at the grain boundary and in the grain while the Ni element as solid solution stays in the austenite grain. The oxidative damage layers can be discovered in both outer and inner surfaces and Cr element in the form of oxide stays at the grain boundary. The mechanical property testing demonstrates that the thermal fatigue and room temperature properties become dramatic decline and the impact rupture shows a typical cleavage fracture.