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Carbide transformation in carburised zone of 25Cr35NiNb+MA alloy after high-temperature service |
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| Authors: | Chunjiao Liu Xuedong Chen Tao Chen Defu Nie Lu Wang |
| Affiliation: | 1. Anhui Provincial Laboratory for Safety Technology of Pressure Vessels and Pipeline, Hefei General Machinery Research Institute, Hefei 230031, P.R. China;2. National Engineering &3. Technical Research Center on Pressure Vessels and Piping Safety, Hefei General Machinery Research Institute, Hefei, 230031, P. R. Chinalcj_sjtu@126.com;5. Technical Research Center on Pressure Vessels and Piping Safety, Hefei General Machinery Research Institute, Hefei, 230031, P. R. China |
| Abstract: | Microstructure evolution due to carburising of a 25Cr35NiNb+MA ethylene pyrolysis furnace tube was investigated after service for approximately 4 years. The microstructure of 25Cr35NiNb+MA alloy was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy (TEM). The results revealed that M23C6 carbides of the 25Cr35NiNb+MA alloy had coarsened and transformed to M7C3 carbides with a heavily faulted structure during carburising. The content of M7C3 carbide increased closer to the inner wall. A large number of dislocations had been observed surrounding the carbides and some formed dislocation walls. The carbide transformation mechanism and the effect of the dislocation walls are discussed. |
| Keywords: | 25Cr35NiNb+MA alloy Carburisation M7C3 M23C6 Dislocation wall |
