CECÍLIO ALVARES DA CUNHA
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Artigo IPEN-doc 23968 Structural and thermodynamic properties of nanocrystalline Cr3C2-25(Ni20Cr) composite powders produced by high-energy ball milling2016 - CUNHA, CECILIO A.; CORREA, OLANDIR V.; SAYEG, ISSAC J.; LIMA, NELSON B.; RAMANATHAN, LALGUDI V.Nanostructured coatings have been used to protect components exposed to severe service conditions. High energy milling is widely used to produce nanocrystalline feedstock of coating materials such as chromium carbide and tungsten carbide. This paper presents the structural and thermodynamic properties of Cr3C2-25(Ni20Cr) powders that were high energy milled for different times. During the high energy milling of Cr3C2-25(Ni20Cr) powder, severe plastic deformation takes place. A small part of the energy spent in this process is stored in the crystal lattice as deformation energy. The crystallite size and microstrain in nanocrystalline Cr3C2-25(Ni20Cr) powders milled for different times were determined by X-ray diffraction measurements. Differential scanning calorimetric (DSC) studies of the milled powders revealed a broad transformation, characteristic of a large exothermic reaction in the nanostructured powder. The enthalpy variation measured by DSC permitted determination of the deformation energy stored in the Cr3C2-25(Ni20Cr) powders milled for different times. These measurements also enabled calculation of the specific heat variation of the milled powders.Resumo IPEN-doc 17963 Effect of high energy milling parameters on WC-Co powder features, composition and thermal stability2011 - PADIAL, A.G.; CUNHA, C.A.; CORREA, O.V.; LIMA, N.B.; RAMANATHAN, L.V.Artigo IPEN-doc 12493 Effect of high energy milling parameters on nanostructured Cr3C2-Ni20Cr powder characteristics2007 - PADIAL, A.; CUNHA, C.A.; AMBROZIO FILHO, F.; BRESSIANI, A.H.A.; MARTINELLI, J.R.; LIMA, N.B. de; RAMANATHAN, L.V.Artigo IPEN-doc 18559 Structural and thermodynamic properties of Crsub(3)Csub(2)-25(Ni20Cr) powders produced by high energy milling2012 - CUNHA, C.A.; CORREA, O.V.; SAYEG, I.J.; LIMA, N.B. de; RAMANATHAN, L.V.Artigo IPEN-doc 18564 Mechanical and structural properties of thermal sprayed Crsub(3)Crsub(2)-25(Ni20Cr) nanocomposite coatings2012 - CUNHA, CECILIO A. da; CORREA, OLANDIR V.; SAYEG, ISSAC J.; LIMA, NELSON B. de; RAMANATHAN, LALGUDI V.Artigo IPEN-doc 16985 Effect of high energy milling on WC-Co powder features, composition and thermal stability2011 - PADIAL, A.G.; CUNHA, C.A. da; CORREA, O.V.; LIMA, N.B. de; RAMANATHAN, L.V.Artigo IPEN-doc 16983 Mechanical and thermodynamic properties of Crsub(3)Csub(2)-25(Ni20Cr) composite powders produced by high energy milling2011 - CUNHA, C.A.; CORREA, O.V.; SAYEG, I.J.; LIMA, N.B. de; RAMANATHAN, L.V.Artigo IPEN-doc 13124 Microstructure and mechanical properties of thermal sprayed nanostructured Cr3C2-Ni20Cr coatings2008 - CUNHA, CECILIO A. da; LIMA, NELSON B. de; MARTINELLI, JOSE R.; BRESSIANI, ANA H.A.; PADIAL, ARMANDO G.F.; RAMANATHAN, LALGUDI V.Cr3C2-Ni20Cr coatings have been used for corrosion and wear resistant applications. However, one of the shortcomings of these coatings is its low hardness, and consequent low wear resistance, for long term high temperature applications. Nanostructured coatings of many materials have exhibited higher hardness and strength compared with conventional coatings of the same material. Consequently, nanostructured coatings of other materials, including Cr3C2-Ni20Cr have been attempted to enhance overall performance. In this study the effects of high energy milling parameters on Cr3C2- 25(Ni20Cr) powder characteristics as well as the microstructure and mechanical properties of nanostructured Cr3C2-25 (Ni20Cr) coatings formed by high velocity oxygen fuel (HVOF) spraying have been evaluated. The average particle size and crystallite size of milled Cr3C2-25 (Ni20Cr) powders decreased with increase in milling time and this decrease was more pronounced in nitrogen compared to that in hexane. This difference has been attributed to a cushioning effect in the latter medium. The coatings prepared with milled Cr3C2-25 (Ni20Cr) powders had a more uniform microstructure, were harder and had higher relative fracture toughness compared with coatings prepared with as-received powders.Artigo IPEN-doc 16523 Effect of Crsub(3)Csub(2)-NiCr powder characteristics on structure and properties of thermal sprayed nanostructured coatings2010 - PADIAL, A.; CUNHA, C.A.; CORREA, O.V.; LIMA, N.B. de; RAMANATHAN, L.V.