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O processo de nitretação tem sido usado com algumas limitações para elevar a resposta ao desgaste dos aços inoxidável martensítico tipo AISI 420. Os problemas estão relacionados à combinação entre endurecimento, resistência à corrosão, desempenho em desgaste e dureza do substrato após o tratamento superficial. Este trabalho apresenta a combinação entre diferentes parâmetros de tratamento térmico e superficial de nitretação sob plasma. Diferentes parâmetros de tratamento térmico foram previamente estudados para atingir durezas de substrato entre 38 HCR e 50 HRC. As amostras foram nitretadas pelo processo de plasma pulsado. As temperaturas de nitretação variaram entre 480°C e 560°C, por tempos entre 1 hora e 16 horas. A caracterização microestrutural utilizou as técnicas de microscopia óptica e de difração de raios X. As durezas do substrato e da superfície foram determinadas pelo método de dureza Rockwell e por microdureza Vickers. A nitretação sob plasma promove um elevado endurecimento, atingindo 1.500 HV. Para substratos tratados para 50 HRC, a temperatura de nitretação tem uma forte influência no endurecimento. Utilizando uma dureza de partida de 38 HRC o endurecimento superficial atinge seu potencial pleno para todas as temperaturas estudadas. Como consequência, são discutidas diferentes rotas de tratamento térmico e superficial. Palavras-chave: Aço inoxidável martensítico; Tratamento térmico; Nitretação sob plasma.

The automobile have more than a hundred years since its invention and the light alloys have been utilized since . In the 's the aluminum did substitute almost completely the casting iron as main component of pistons. In the same decade, in Germany, magnesium alloys were utilized in the production of camshaft and in the gear box, which leads, at that time, the total decrease of weight at least % of the total of the automobile.Magnesium alloy developments have traditionally been driven by aerospace industry requirements for lightweight materials to operate under increasingly demanding conditions. In the last decade several heavy magnesium parts have been assembled in passenger cars, such as gear box housings and crank cases "ghion, .Considerable research is still needed on magnesium processing, alloy development, joining, surface treatment, corrosion resistance, and mechanical properties improvement. Surface coatings produced for magnesium die-casting by hexavalent chromium baths have been used to provide stand-alone protection and as a pretreatment for painting. Teflon resin coating has been developed for Mg alloys initially the coating is obtained with an aluminum vapor deposition and finish treatment with a Teflon resin coating. The Teflon resin coating is a low cost, chromium-free corrosion resistant coating for magnesium alloys. The coating not only has corrosion resistant properties, but also good lubricity, high frictional-resistance and non-wetting properties Kulekci, .These new projects are concerned on the modification of existing and the development of new magnesium wrought products sheets and extrusions , that provide significantly improved static and fatigue strength properties for lightweight fuselage applications Development of material models and failure criteria for the prediction of forming processes, plastic deformation and failure behavior of components material adapted design and the evaluation of structural behavior to close the process and development chain for aeronautic components .The specific strength properties of these innovative materials are required to be higher than "" for structural applications secondary structure and higher than "" for nonstructural applications. "t the beginning of the project new alloys will be developed and experimental alloys will be tested. "ppropriate manufacturing rolling, extrusion , forming and joining technologies require development, simulation and validation for the innovative material and application Hombergsmeier, . The technological objective is a weight reduction of the fuselage structure, system and interior components up to %. The strategic objectives are an increase in the operational capacity of %, a reduction in the direct operating cost of % and finally a reduction in the fuel consumption of % and therefore a reduced environmental impact with regard to emissions and noise Hombergsmeier, . Magnesium Alloys 2Regarding corrosion is also a problem to be solved with newly adapted surface protection systems according to aerospace requirements and...

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is a physicist, MSc (Solid State Physics), DSc (Nuclear Technology) at the University of São Paulo (USP)/São Paulo/ SP /Brazil. He is a senior researcher in the Materials Science and Technology Center at IPEN (Nuclear and Energy Research Institute). Also, he is lecturer and scientific advisor (MSc and DSc) on graduate course on IPEN -USP. His expertise areas are physical metallurgy, powder metallurgy, nuclear technology (materials), and materials characterization (optical and electron microscopy; microanalysis techniques). He has published more than 150 articles (scientific journals and congress proceedings), chapters, and books in material sciences area. The academic advisories include 50 scientific initiations (undergraduate students), 28 Masters of Science, and 14 Doctors of Science. Contents Preface XIII Section Ionic Materials 1