caa a22 4500 44584387X CHVBK 20180317145352.0 cr unu---uuuuu 170323e20110401xx s 000 0 eng 10.1007/s11085-010-9230-6 doi (NATIONALLICENCE)springer-10.1007/s11085-010-9230-6 Cyclic Oxidation Behavior of IN 718 Superalloy in Air at High Temperatures [Elektronische Daten] [Kh. Al-hatab, M. Al-bukhaiti, U. Krupp, M. Kantehm] Ni-base superalloy IN 718 was cyclically oxidized in laboratory air at temperatures ranging from 750 to 950°C for up to 12 cycles (14h/cycle). The kinetic behaviour as well as the surface morphology, and the oxide phases of the scales were characterized by means of weight gain measurements, cyclic oxidation kinetics, scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) analysis techniques. The results showed that as the oxidation temperature increased, the oxidation rate, the external scale thickness, and internal oxidation zone increased. It was suggested that the oxidation rate was controlled by the diffusion of substrate elements in the alloy and the inward diffusion of oxygen through the oxide scale. The oxidation kinetics followed a sub-parabolic rate law and, the activation energy of oxidation was 249±20kJmol−1. The scaling process was controlled mainly by the diffusion of chromium, titanium, manganese, and oxygen ions through the chromia scale. IN 718 showed low weight gain and very slow reaction rates of substrate elements at 750°C. At 850°C, a continuous and very thin oxide scale was formed. At 950°C, XRD and EDS-elemental mapping analysis revealed that a complex oxide scale had formed. It consisted of an outermost layer of TiO2-MnCr2O4 spinels, inner layer of Cr2O3, and the inner most layer composed of Ni3Nb enriched with Nb, Ti and Al oxides underneath the chromia layer. The oxide scale at this temperature seemed to be thicker layer, significant spallation and volatilization had apparently occurred, and greater internal corrosion was identified. The doping effect of titanium was observed, where it was found to be diffused through the chromia scale to form TiO2 at the oxide-gas interface as well as internally and at the oxide alloy interface. The amount of rutile (TiO2) at the oxide surface increased with temperature. In view of Mn contents in the alloy, the manganese-chromium spinel oxide was inferred to have played an important role in cyclic oxidation behaviour of IN 718, where the change in oxidation kinetic was noted. The Al contents would cause internal Al-rich oxide formation at grain boundaries. Springer Science+Business Media, LLC, 2010 Cyclic oxidation nationallicence IN 718 superalloy nationallicence Parabolic rate nationallicence Activation energy nationallicence Doping nationallicence Spinel nationallicence Al-hatab Kh Mechanical Engineering Department, Faculty of Engineering, Sanaá University, Sanaa, Yemen aut Al-bukhaiti M. Mechanical Engineering Department, Faculty of Engineering, Sanaá University, Sanaa, Yemen aut Krupp U. Faculty of Engineering and Computer Science, University of Applied Science, Osnabrück, Germany aut Kantehm M. Faculty of Engineering and Computer Science, University of Applied Science, Osnabrück, Germany aut Oxidation of Metals Springer US; http://www.springer-ny.com 75/3-4(2011-04-01), 209-228 0030-770X 75:3-4<209 2011 75 11085 https://doi.org/10.1007/s11085-010-9230-6 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11085-010-9230-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Al-hatab Kh Mechanical Engineering Department, Faculty of Engineering, Sanaá University, Sanaa, Yemen aut NATIONALLICENCE 700 1- Al-bukhaiti M. Mechanical Engineering Department, Faculty of Engineering, Sanaá University, Sanaa, Yemen aut NATIONALLICENCE 700 1- Krupp U. Faculty of Engineering and Computer Science, University of Applied Science, Osnabrück, Germany aut NATIONALLICENCE 700 1- Kantehm M. Faculty of Engineering and Computer Science, University of Applied Science, Osnabrück, Germany aut NATIONALLICENCE 773 0- Oxidation of Metals Springer US; http://www.springer-ny.com 75/3-4(2011-04-01), 209-228 0030-770X 75:3-4<209 2011 75 11085 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer