OLANDIR VERCINO CORREA
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Artigo IPEN-doc 27389 Surface chemistry and semiconducting properties of passive film and corrosion resistance of annealed surgical stainless steel2020 - OLIVEIRA, RODRIGO K. de; CORREA, OLANDIR V.; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.ASTM F-139 surgical stainless steel was subjected to annealing treatments at 700 °C for different times. The effect of annealing on the chemical composition of the passive film was evaluated by x-ray photoelectron spectroscopy. The correlation of the surface chemistry with the corrosion behavior and semiconducting properties of the passive film was also investigated. Potentiodynamic polarization tests were conducted in phosphate-buffered solution at 37°C. The semiconducting character of the passive film was assessed by the Mott–Schottky approach. The microstructure of the annealed samples was characterized by optical microscopy. The grain size increased after annealing, but the differences between each annealing condition were not significant and could not be associated with the corrosion behavior of the annealed samples. The corrosion resistance was improved depending on the heat treatment condition due to compositional changes of the passive film upon annealing. The best corrosion properties were observed after annealing for 8 h which was ascribed to Cr2O3, MoO3 and FeO enrichment in the passive film.Artigo IPEN-doc 24819 Influence of the tungsten content on surface properties of electroless Ni-W-P coatings2018 - OLIVEIRA, MARA C.L. de; CORREA, OLANDIR V.; ETT, BARDIA; SAYEG, ISAAC J.; LIMA, NELSON B. de; ANTUNES, RENATO A.Ternary Ni-W-P films were produced by electroless deposition using baths with different tungsten concentrations. After deposition, the coated surfaces were annealed at 400°C for 1h. Surface morphology and film composition in the as-plated condition were assessed by SEM and EDS analyses, respectively. The crystalline phases after annealing were investigated by X-ray diffraction (XRD). Nanoindentation tests were performed to assess the mechanical properties of the deposited films. Surface roughness was determined by confocal laser scanning microscopy (CLSM). Friction coefficient was evaluated by reciprocating were tests in a nanotribometer. The corrosion behavior was evaluated by potentiodynamic polarization curves. The results showed that the surface morphology, crystallization behavior and corrosion resistance were affected by the tungsten content in the film. The best corrosion performance was obtained for the ternary films after annealing. Hardness, surface roughness and friction coefficient were dependent of the tungsten concentration in the film.Artigo IPEN-doc 23482 High temperature erosion-oxidation resistance of thermally sprayed nanostructured Cr3C2-25(Ni-20Cr) coatings2017 - CUNHA, CECILIO A. da; CORREA, OLANDIR V.; SAYEG, ISAAC J.; RAMANATHAN, LALGUDI V.This study reports the high temperature erosion-oxidation (E-O) behavior of conventional and nanostructured Cr3C2-25(Ni-20Cr) coatings prepared by high velocity oxygen fuel (HVOF) spraying. As-received and nanostructured Cr3C2-25(Ni-20Cr) powders with mean crystallite sizes of 145 nm and 50 nm respectively, were used to prepare 120 - 200 μm thick coatings on AISI 310 samples. The E-O behavior of the coatings prepared with the as-received (AR) and nanostructured (NS) powders was determined as weight change in a custom designed rig at room temperature, 450, 700 and 800 ºC. The Vickers microhardness, Young’s Modulus and fracture toughness of the AR and NS coatings were determined, and the NS coatings exhibited higher values compared with the AR coatings. The E-O resistance of the NS coating was higher than that of AR coating at all temperatures, and particularly at 800 ºC. The increase in E-O resistance of the NS coatings is due to its superior mechanical properties as well as to the presence of some heterogeneities in the AR coatings. The E-O mechanisms of both types of the coatings are discussed, with special attention to that at high temperatures. The results suggest that at 800 ºC the E-O process is controlled by erosion of the oxide.Artigo IPEN-doc 22413 High temperature oxidation behavior of yttrium dioxide coated Fe-20Cr alloy2016 - PILLIS, MARINA F.; CORREA, OLANDIR V.; RAMANATHAN, LALGUDI V.Artigo IPEN-doc 21711 Effect of processing on microstructure and corrosion mitigating properties of hydrotalcite coatings on AA 6061 alloy2015 - FERNANDES, STELA M. de C.; CORREA, OLANDIR V.; SOUZA, JOSE A.B. de; ANTUNES, RENATO A.; LIMA, NELSON B. de; RAMANATHAN, LALGUDI V.