The microstructure evolution and mechanical properties change of Cr35Ni45Nb heat-resistant steel used in pyrolysis furnace after a six-year service
To understand the microstructure degradation of heat-resistant steel used in pyrolysis fumaee tube, the microstructure evolution of Cr35Ni45Nb heat-resistant steel from a six-year serviced tube at 1100 ℃ was investigated and compared with that from an as-cast tube.Moreover, the stress rupture test and hardness were examined to investigate the mechanical properties of the heat-resistant steel.The results show that a continuous network primary carbides and agglomeration of secondary carbides formed in the substrate after service, where some primary carbides transformed into Cr23C6 and G phase.The outer surface of the steel was composed of a continuous Cr2O3 and SiO2 layer and the beneath layer of a Cr-depleted zone.However, four regions were identified in the inner surface due to cyclic carburizing and oxidizing: initial oxidation, the Cr-depleted zone formation, silicon oxide formation and carbides transformation.Significant decrease in creep strength was observed after service, which is possibly attributed to the microstructure degradation by the coarse primary carbides and the carbides transformation.
microstructure evolution pyrolysis furnace carbide carburization oxidation
GUO Jingfeng CHENG Congqian LI Huifang ZHAO Jie MIN Xiaohua
School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
国际会议
长沙
英文
110-115
2016-10-16（万方平台首次上网日期，不代表论文的发表时间）