Study on microstructure and properties of centrifugal casting 35Cr45NiNb+MA furnace tubes during service. (2nd November 2019)

• Record Type: Journal Article
• Authors: Hu, Biao; Chen, Xuedong; Liu, Chunjiao; Lian, Xiaoming; Chen, Tao
• Is Part Of: Materials at high temperatures. Volume 36:Number 6(2019)
• Page Start: 489
• Page End: 498
• Publication Date: 2019-11-02
• Subjects: 35cr45ninb+MA -- high-temperature ageing -- M23C6 -- M7C3 -- carburising -- microstructure evolution -- properties -- map; Materials at high temperatures -- Periodicals; High temperatures -- Periodicals; 620.1121705
• DOI: 10.1080/09603409.2019.1640511
• Languages: English
• ISSNs: 0960-3409

Abstract

ABSTRACT: In the present study, the microstructure evolution of 35Cr45NiNb+MA ethylene cracking furnace tubes during service and its effect on the properties were investigated. According to the results, in the early stage of service, the skeletal M7 C3 and vermicular NbC were transformed into blocky M23 C6 and G phase (Ni16 Nb6 Si7 ), respectively, accompanied with many dispersed M23 C6 secondary carbides. With the extension of service time, M23 C6 carbides on the grain boundaries were transformed into M7 C3 with high stacking fault structure and coarsened, and the blocky G phase was transformed into granular NbC. The yield strength and ultimate tensile strength of the aging furnace tubes decreased by 9%-18%, yet the elongation after fracture decreased significantly from 10.0%-14.0% to 3.0%-5.0%. The hardness of the carburized zone of the carburized tubes increased by 10%-17%, and the rupture time decreased by 45%-75% under the test condition of 1100℃ and 16MPa. Finally, the evolution map was summarized.