OLANDIR VERCINO CORREA

OLANDIR VERCINO CORREA

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Effect of nanocrystalline mixed rare earth oxide coatings on the high temperature oxidation behavior of Fe20Cr5Al alloy
2014 - FERNANDES, STELA M.C.; CORREA, OLANDIR V.; RAMANATHAN, LALGUDI V.
Rare earths (RE) have been used to improve high temperature oxidation resistance of chromium dioxide and alumina forming alloys. The RE can be added to the alloy as elements or as oxide to form dispersions. It can also be applied as a RE oxide coating to the surface of the alloy. In this investigation the sol-gel technique was used to prepare sols of the RE oxides as it produces nanocrystalline oxide particles. In an effort to increase further the oxidation resistance of high temperature alloys, optimization of RE oxide additions to the alloy surface has been attempted. This paper presents the effect of nanocrystalline oxide gel coatings of CeO2, Nd2O3, Pr2O3, CeO2 + Nd2O3, CeO2 + Pr2O3 and Pr2O3 + Nd2O3 on the oxidation behavior of Fe20Cr5Al alloys at 1100 °C. The individual oxides decreased oxidation rate. However, the CeO2 + Nd2O3 mixture did not increase oxidation resistance of the alloy further, compared to those with either one of these two rare earth oxides. The Pr2O3 + CeO2 mixture increased oxidation resistance of the alloy markedly where as the mixture Nd2O3 to Pr2O3 had no significant effect. The differences in the influence of a specific rare earth oxide or a mixture are attributable to differences in the ionic radii of the RE and the morphology as well as the crystallite sizes of the RE oxides.
Nanocrystalline rare earth oxide coatings for increased protection of iron-chromium alloys at high temperatures
2014 - FERNANDES, STELA M.C.; CORREA, OLANDIR V.; RAMANATHAN, LALGUDI V.
Effect of sol-gel preparation technique of mixed nanocrystalline rare earth oxide coatings on high temperature oxidation behavior of Fesup(2)0Cr5al alloy
2014 - FERNANDES, S.M.C.; CORREA, O.V.; RAMANATHAN, L.V.
Nanostructured coatings to protect metallic materials at high temperatures
2013 - FERNANDES, S.M.C.; PILLIS, M.F.; CUNHA, C.A.; CORREA, O.V.; RAMANATHAN, L.V.
Effect of temperature and erodent velocity on erosion-oxidation behaviouir of steels AISI 1020, 410, 304 and 310
2008 - FERNANDES, S.M.C.; CORREA, O.V.; RAMANATHAN, L.V.
Cyclic oxidation resistance of rare earth oxide gel coated Fe-Cr alloys
2006 - FERNANDES, S.M.C.; CORREA, O.V.; RAMANATHAN, L.V.
Use of rare earths to increase high temperature oxidation resistance of chromium dioxide and alumina forming alloys is well known. Rare earth oxide coatings obtained by the solgel technique have been found to be very efficient to apply fine oxide coatings. The cyclic oxidation resistance (RT-900ºC) of Fe-Cr alloy coated with various rare earth oxide gel coatings (La2O3, CeO2, Pr2O3, Nd2O3, Sm2O3, Gd2O3, Dy2O3, Y2O3, Er2O3, and Yb2O3) was determined. Specimens coated with La2O3 and Pr2O3 gels were found to be the most resistant to cyclic oxidation. In an extension of this study, the effect of cooling rate, (and consequently thermal shock resistance) from the peak temperature (900ºC, 1000ºC, 1100ºC) to room temperature of specimens coated with La2O3 and Pr2O3 gels was studied. The morphology and coverage of the rare earth oxide gels varied with the type of rare earth. The cyclic oxidation resistance increased with increase in time at temperature required to reach a specific chromium dioxide layer thickness. This in turn was influenced by rare earth ion radius and other characteristics of the rare earth oxide coating such as morphology, stability, coverage, resistance to thermal stresses and adhesion.
Effect of mixed rare earth oxide coatings on high temperature oxidation of Fe-20Cr alloy
2010 - FERNANDES, S.M.C.; CORREA, O.V.; RAMANATHAN, L.V.
High temperature erosion-oxidation behavior of steels
2007 - FERNANDES, S.M.C.; CORREA, O.V.; RAMANATHAN, L.V.
High temperature erosion-oxidation behavior of steels
2008 - FERNANDES, S.M.C.; CORREA, O.V.; RAMANATHAN, L.V.
The high temperature erosion-oxidation (E-O) behavior of steels AISI 1020, 304, 310 and 410 was determined. A test rig in which a specimen assembly was rotated through a fluidized bed of erodent particles was used to determine the E-O behavior. Alumina powder (200µm) was used as the erodent. The E-O tests were carried out in the range 25 - 600ºC, with average particle impact velocities of 6, 14 and 30 ms-1 at an impact angle of 90º. In the E-O tests, wastage of the steels varied with temperature and particle impact velocity (PIV). Depending on PIV, a transition in the dominant wastage mechanism occurred and the transition temperature varied with steel composition. Variation in Cr content of the steels did not affect wastage at low PIV. AISI 410 with 12% Cr revealed the lowest wastage at 30 ms-1 compared to AISI 304 and 310. E-O maps of the steels were prepared as a function of PIV and temperature. Low, moderate and severe wastage zones were indicated in these maps to aid selection of these steels for industrial applications.