Characterization of an ASTM A335 P91 ferritic-martensitic steel after continuous cooling cycles at moderate rates

Denise Alejandra Carrizo, Jorge Ignacio Besoky, María Luppo, Claudio Danon, Cinthia Paula Ramos
2018 Journal of Materials Research and Technology  
j m a t e r r e s t e c h n o l . 2 0 1 9;8(1):923-934 w w w . j m r t . c o m . b r Scanning and transmission electron microscopy X-ray diffraction Mössbauer spectroscopy a b s t r a c t In this contribution some aspects of the behavior of the ASTM A335 P91 (9Cr1MoVNbN) steel subjected to continuous cooling cycles under fixed austenitization conditions are studied. Representative samples of the structures obtained after cooling at moderate rates (i.e. pure martensitic and mixed
more » ... xed martensitic-ferritic) were analyzed in order to incorporate information to the Continuous Cooling Transformation (CCT) diagram of this material. The characterization was carried out by means of scanning and transmission electron microscopy (TEM), X-ray diffraction and Mössbauer spectroscopy. For the working conditions here employed, the results showed the existence of retained austenite within both, the pure martensitic and the mixed martensitic-ferritic domains of cooling rates, adding important information to the CCT diagram since retained austenite presence could be detrimental to the mechanical properties of the steel. Second phase precipitates, being relevant to fix the mechanical behavior of the material, were identified by means of TEM on carbon replicas. Mössbauer spectroscopy was very helpful to detect a low volume fraction of cementite-type phase in all of the samples, considering that it could not be conclusively determined by XRD due to orientation effects. (C.P. Ramos). heat exchangers, piping and tubing, etc., due to an excellent combination of properties such as creep resistance, toughness and corrosion resistance at high temperatures. In the four last decades, 9%Cr1%Mo-based modified alloys have also been designed and studied for applications as structural materials in the new generation of nuclear fission reactors, expected to work at high to very high temperatures (Generation IV reactors) and in fusion reactors as well. These new envisaged applications have raised very exigent requirements, as https://doi.
doi:10.1016/j.jmrt.2018.07.004 fatcat:cz4dzdwelfbcnki4ftexwil5bm