Microstructure evolution and residual life assessment of service exposed Cr35Ni45 radiant tube alloy. (June 2018)

• Record Type: Journal Article
• Authors: Song, Ruokang; Wu, Sujun
• Is Part Of: Engineering failure analysis. Volume 88(2018)
• Page Start: 63
• Page End: 72
• Publication Date: 2018-06
• Subjects: Radiant tube -- Phase transformation -- Carbide -- Oxidation -- Residual life; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2018.01.002
• Languages: English
• ISSNs: 1350-6307

Abstract

Abstract: The degradation of material microstructure was frequently encountered in radiant tubes during high temperature service, resulting in their premature failure. Effect of service time on the phase transformation and oxidation behavior of the Cr35Ni45 radiant tubes was analyzed using scanning electron microscopy (SEM), electronic probe coupled with wavelength dispersive spectrometer, X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The orthorhombic M7 C3 and the face-centered cubic NbC primary carbides in the as-cast tube transformed into the face-centered cubic M23 C6 and the face-centered cubic G phase, respectively, during service at 1000 °C. Metallographic observation showed that a continuous Cr2 O3 layer and a discontinuous SiO2 layer formed on the inner surface of the radiant tubes due to the oxidizing environments, and a precipitate free region was found beneath the oxide layers. Mechanical properties of the tubes decreased with the increasing degree of microstructure degradation as service time prolongs. Residual life assessment of the serviced tubes was conducted by nonlinear fitting Larson–Miller parameter versus rupture testing stress. In spite of lower mechanical properties for the serviced tubes compared to as-cast tube, residual life assessment indicates that they have considerable residual life at the service temperature. Graphical abstract: Highlights: Microstructure evolution after service exposure was characterized by electron metallography. Phase stability at high temperature was analyzed using thermodynamic calculation. Internal and external oxidation behavior of the tubes was evaluated based on Wagner theory. A remaining life prediction model for Cr35Ni45 tube alloy was proposed.