MAURILIO PEREIRA GOMES

MAURILIO PEREIRA GOMES

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Microstructural characterization of air quenched valve seat inserts obtained with AISI D2 tool steel
2017 - GOMES, M.P.; SANTOS, I.P.; COUTO, C.P.; BETINI, E.G.; COLOSIO, M.A.; ROSSI, J.L.
The obtention of valve seat insert (VSI) by powder metallurgy using a mixture of iron powder and tool steel is fulfilling the requirements for substitution of cobalt and lead in commercial parts, aiming cost reduction and avoid the lead toxicity. The aim of this work consisted of evaluate the influence of heat treatment on VSI obtained with AISI D2 tool steel powder. The AISI D2 tool steel powder was mixed with iron powder and additives such as manganese sulphide, zinc stearate, graphite and carbides. The heat treatment of the VSI consisted of air quenching followed by double tempering it at 500 °C. The microstructural characterization was performed using scanning electron microscopy and energy dispersive spectroscopy.
Influence of heat treatment on corrosion resistance of press hardened steel coated with AlSi and ZnNi
2017 - COUTO, CAMILA P.; COSTA, ISOLDA; COLOSIO, MARCO; GOMES, MAURILIO; ROSSI, JESUALDO; BOLSANELLO, MARILIA
The ultrahigh strength boron manganese steels, also known as PHS (press hardened steels), are strategic materials for the automotive industry, satisfying safety needs and fuel reduction requirements by means of the lightweight design concept, a current trend for new vehicles. It is possible by the hot stamping process which consists in heating a steel blank to the austenitization temperature, transferring it to press tooling, forming and quenching to fully martensitic transformation. At the end of process, the steel achieves tensile strength up to 1,500 MPa. The transference step from furnace to press is a critical stage because it might promote deleterious steel oxidation. The use of metallic coatings avoids this outcome. AlSi coatings have been the most applied on PHS. Alternative coatings such as electroplated ZnNi are under investigation to evaluate their potential for replacement of AlSi coatings, besides to keep up with the high projected world demand. Zinc based coatings are advantageous comparatively to AlSi ones because they provide cathodic protection to steel substrates. In this study the influence of hot stamping heat treatment on corrosion resistance of 25MnB5 steel coated by AlSi and electroplated ZnNi has been investigated. The tests include open circuit potential measurement, electrochemical impedance spectroscopy and anodic polarization curves. The samples have been tested as received and after the heat treatment which consists in heating the sample at 900°C by 10 minutes and then, fast cooling in water. It is expect that the heat treatment changes the corrosion resistance due to the intermetallics formation at the coating layer as a consequence of diffusion.
Characterization of sintered valve seat inserts obtained with AISI M2 high-speed steel after air quenching
2017 - GOMES, MAURILIO P.; SANTOS, IGOR P. dos; REIS, LUIS A.M. dos; COUTO, CAMILA P.; MUCSI, CRISTIANO S.; COLOSIO, MARCO A.; ROSSI, JESUALDO L.
The aim of this work was to heat treat and characterize sintered valve seat inserts (VSI). The powder metallurgy route was the only way found to substitute cobalt and lead, used in the VSI original alloy, due to their high cost and toxicological effect, respectively. The studied VSI was obtained with AISI M2 high-speed steel powder mixed with iron powder and other additives such as manganese sulphide, graphite, zinc stearate, carbides and copper, which was added by metallic infiltration. All the VSI were air quenched and double tempered, for one hour each, at seven different equidistantly temperatures, ranging from 100 °C up to 700 °C. The physical and mechanical properties were evaluated by means of the VSI apparent density, apparent hardness and crush radial strength. The chemical composition was determined through gas analysis, for the light elements such as carbon and sulfur, and energy dispersive X-ray fluorescence spectrometry for other elements. Microstructural characterization was performed with the support of scanning electron microscopy and energy dispersive spectroscopy. Regarding the VSI final application, the best results were achieved with the inserts air quenched and double tempered at 600 °C.
Characterization of PHS coating layer using GDOES technique
2017 - COUTO, C.P.; GOMES, M.P.; COSTA, P.D.O.; COLOSIO, M.A.; POLITANO, R.; ROSSI, J.L.
O objetivo do estudo foi analisar o perfil de composição química do revestimento Al-Si em aços PHS, por meio da técnica de GDOES. Devido às elevadas temperatura no processo de estampagem a quente ocorre à difusão dos elementos do revestimento e do substrato. Os resultados revelaram que na amostra como recebida, o revestimento apresenta grandes porcentagens de alumínio, silício e oxigênio, que se difundem e diminuem de concentração em direção ao substrato, enquanto que a porcentagem de ferro aumenta. Os resultados das amostras tratadas termicamente em laboratório e do produto final são muito similares, o que indica que o tratamento térmico realizado em laboratório simula corretamente o processo térmico da estampagem industrial. O revestimento é formado por alumínio e ferro, que variam uniformemente até atingir o substrato onde a porcentagem de alumínio diminui em relação à de ferro. A camada revestida também é composta por oxigênio e silício que se difundem em direção ao substrato, onde a porcentagem de oxigênio diminui gradativamente e a de silício não se altera. Os resultados de GDOES mostraram as alterações que ocorrem na camada revestida do aço PHS, e evidenciaram que após o processo de estampagem a quente podem ser formados óxidos e fases compostas por Al-Fe ou Al-Fe-Si.
Valve seat insert: air quenching and characterization of components obtained with AISI M3:2 high-speed steel
2018 - GOMES, M.P.; SANTOS, I.P.; REIS, L.A.M.; COUTO, C.P.; BETINI, E.G.; MUCSI, C.S.; COLOSIO, M.A.; ROSSI, J.L.
The development of components ecologically correct is something more and more necessary. The first developement of valve seat inserts (VSI) take in account the use of cobalt and lead in its chemical composition. Such elements are avoided in the current applications due to its high cost and toxicological effects, respectively. In the present work was used VSI developed with a new chemical composition. The aim of this work were to air quench and characterize such components. The studied VSI were obtained with AISI M3:2 high-speed steel admixed with iron powder and another additives such as manganese sulphide, graphite, zinc stearate and carbides. All the air quenched VSI were double tempered, for one hour each, at seven equidistant temperature from 100 °C until 700 °C. The air quenched components had its mechanical and physical properties determined by means of its apparent density, apparent hardness and crush radial strength. The chemical composition was measured through the gases analyses and energy dispersive X-ray fluorescence spectrometry techniques. Microstructural and phase characterizations were performed with the support of optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Regarding the VSI required properties, the best results were obtained with the components air quenched and double tempered at 600 °C.
Heat treatment of sintered valve seat inserts
2018 - GOMES, MAURILIO P.; SANTOS, IGOR P. dos; COUTO, CAMILA P.; BETINI, EVANDRO G.; REIS, LUIS A.M. dos; MUCSI, CRISTIANO S.; COLOSIO, MARCO A.; ROSSI, JESUALDO L.
The characterization of sintered valve seat inserts (VSIs) after being subjected to different heat treatment operations has been carried out. The VSIs were obtained from three different alloys by mixing iron powder with AISI M3:2, AISI M2 high-speed steels, and AISI D2 tool steel. After sintering, the VSI were quenched in air followed by double tempering at seven different temperatures. The cooling rate during air quenching was measured by means of a thermocouple type k attached to a data acquisition system. The characterization of the mechanical and physical properties of the VSIs was achieved by measuring relative density, apparent hardness and crush radial strength. The resulting microstructures for the sintered parts were interpreted using the isothermal and continuous cooling transformation diagrams for similar alloys. The VSI obtained with AISI M3:2 and AISI M2 high-speed steels after air quenching and double tempering at 600 ºC showed the best results in terms of apparent hardness and crush radial strength.
Diffusion analyses using GDOES technique of the 22MnB5 press hardened steel with Al-Si and Zn-Ni coatings
2018 - COUTO, C.P.; POLITANO, R.; GOMES, M.P.; COLOSIO, M.A.; ROSSI, J.L.
The hot stamping process consists to heat the steel blank, at total austenitization temperatures and to transfer it into the press tooling for forming and fast cooling to fully martensitic transformation. This transference from furnace to press stage promotes some steel oxidation. The application of metallic coatings avoids this phenomenon. The Al-Si coating, a patented process, has been the most applied on steel. Hence, alternative coatings like Zn-Ni are under development. It is known that this furnace heating causes chemical elements diffusion that results in intermetallics formation. This study had the objective of analyze the diffusion profiles of chemical elements present in the substrate, 22MnB5 steel, and coatings of Al-Si and Zn-Ni, using glow-discharge optical emission spectroscopy - GDOES and to correlate the results with those obtained with energy dispersive X-ray spectroscopy - EDS. The results showed that for the Zn-Ni sample, the Zn and Fe profiles at the interfacial zone, are predominant; which justify the high proportion of ZnFe phases as showed using scanning electron microscopy - SEM images. For the Al-Si sample at the interfacial zone, the profile of Al and Fe varies simultaneously; besides that, silicon diffusion in the substrate is more effectively than the nickel diffusion. For this reason, it was possible to identify AlFeSi phase near to the steel substrate.
Têmpera ao ar de insertos de assentos de válvulas obtidos com aço ferramenta AISI D2
2017 - GOMES, MAURILIO P.; SANTOS, IGOR P. dos; COUTO, CAMILA P.; MUCSI, CRISTIANO S.; COLOSIO, MARCO A.; ROSSI, JESUALDO L.
A obtenção de insertos de assentos de válvulas por metalurgia de pó usando uma mistura de pó de ferro e aços rápidos ou aços ferramenta está atendendo os requisitos para a substituição do cobalto e chumbo em peças comerciais, visando a redução de custo e evitando a toxicidade do chumbo. O objetivo do presente trabalho foi o de tratar termicamente e caracterizar os insertos de assentos de válvulas sinterizados obtidos utilizando-se uma mistura de pós. Essa mistura de pós foi constituída pelo aço ferramenta AISI D2, ferro, sulfato de manganês, carboneto de nióbio, grafite, estearato de zinco e cobre. O ciclo de temperatura da têmpera ao ar foi determinado por meio do termopar tipo k acoplado a um sistema de aquisição de dados. As propriedades físicas e mecânicas foram medidas em relação à dureza aparente dos insertos, densidade aparente e a sua resistência à ruptura radial. A caracterização microestrutural foi realizada utilizando-se a microscopia óptica, microscopia eletrônica de varredura e espectroscopia por dispersão de energia. Os insertos temperados ao ar e duplamente revenido a 500 °C mostraram os melhores resultados no que tange a dureza e resistência à ruptura radial.
P/M valve seat inserts: air quenching and characterization
2017 - GOMES, MAURILIO P.; SANTOS, IGOR; COUTO, CAMILA; MUCSI, CRISTIANO; ROSSI, JESUALDO L.; COLOSIO, MARCO
This work consists of evaluating the influence of heat treatment on sintered valve seat insert (VSI) obtained with two different highspeed steels powders and one tool steel: AISI M3:2, AISI M2 and AISI D2, respectively. The high-speed / tool steel powders were mixed with iron powders and additives such as manganese sulphide, zinc stearate, graphite and niobium carbide. All the high-speed / tool steel powders had its particle size distribution and morphology analyzed. The heat treatment of the VSI consisted of air quenching followed by double tempering it in seven different and equidistant temperatures, ranging from 100 °C until 700 °C. A data acquisition system with a thermocouple type k attached to the samples was used to determine the air-quenching cooling rate. The mechanical and physical properties measurements were carried out, i.e., apparent density, apparent hardness and crush radial strength. The microstructural evaluation consisted of etching the VSI and then analyzing it using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the VSI obtained with the AISI M3:2 and M2 high-speed steel powders mixtures showed the best results regarding its apparent hardness and crush radial strength after air quenching and double tempering it at 600 °C.
Têmpera ao ar de insertos de assentos de válvulas obtidos com o aço ferramenta AISI D2
2017 - GOMES, MAURILIO P.; SANTOS, IGOR P. dos; COUTO, CAMILA P.; MUCSI, CRISTIANO S.; ROSSI, JESUALDO L.; COLOSIO, MARCO A.