CAMILA PUCCI COUTO

CAMILA PUCCI COUTO

Página do item completo

Resultados de Busca

Agora exibindo 1 - 8 de 8

Influence of hot-stamping process on the corrosion initiation and properties of corrosion products at the surface of 22MnB5 steel metallic coated with hot-dip Al-Si
2021 - COUTO, CAMILA P.; BAERT, KITTY; COSTA, ISOLDA; PANOSSIAN, ZEHBOUR; DE GRAEVE, IRIS; REVILLA, REYNIER I.; TERRYN, HERMAN; ROSSI, JESUALDO L.
22MnB5 is an ultra-high strength steel combined with hot-stamping process, also known as press hardened steel (PHS). It is a strategic material for the automotive industry because it allows safety improvement, lightweight design and consequently reduction of fuel consumption. In order to prevent surface scale and steel decarburisation during the hot-stamping process, the material is often protected with metallic coatings. Hot-dip Al-Si (Si 10 % in mass fraction) is the most used system for hot-stamping application. This study has the objective to characterize the corrosion initiation and the properties of the corrosion products at the surface of samples before and after hot-stamping process. The samples were submitted to several cycles of accelerated corrosion tests in a salt spray chamber. A systematic characterization of the corroded surface was done by means of Raman spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM - EDS). The samples were also immersed in a Cl– containing solution, after which the morphology of the corrosion attacks and the corrosion initiation process were studied. The thermo-mechanical process changes the corrosion mechanism as well as the nature of the corrosion products.
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.
Investigation of electrochemical behaviour of 22MnB5 steel coated with hot-dip Al-Si before and after hot stamping process by means of SKPFM measurements
2019 - COUTO, CAMILA P.; REVILLA, REYNIER; COSTA, ISOLDA; PANOSSIAN, ZEHBOUR; ROSSI, JESUALDO; TERRYN, HERMAN; DE GRAEVE, IRIS
The demand for hot stamped components has been growing in structural vehicle applications, due to the advantages of combining lightweight design and safety improvement. Boron-manganese 22MnB5 steel is the most common grade for hot stamping applications. After the thermomechanical process, the steel exhibits up to 1,500 MPa of tensile strength with the absence of the springback effect. The hot stamping process involves heating the steel blank to the austenitization temperature and then transferring it from the furnace to the press tool, where the material is formed and quenched simultaneously. Due to high temperatures during the process, the steel blank is protected with a metallic coating to avoid the steel decarburization and oxidation. Hot-dip Al-Si is the most applied coating system on boron-manganese steel for hot stamping applications. It is known that, during hot stamping, diffusion takes place changing the coating layer morphology. The objective of this study is to investigate the effect of the hot stamping process on the electrochemical behaviour of 22MnB5 steel coated with hot-dip Al-Si by means of the SKPFM technique. Moreover, the samples were characterized by means of FE-SEM/EDS. The SKPFM results showed that, before the hot stamping process, there is a high difference of potential between the coating layer and the steel substrate. After hot stamping, this difference decreases. In both conditions (before and after hot stamping), the coating layer is less noble than the steel substrate. It was also observed that the steel substrate potential also decreased after the hot stamping process. This could be a consequence of iron diffusion towards the coating layer and the recrystallization of the substrate after the thermo-mechanical process.
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.
The use of scanning vibrating electrode technique to evaluate the effect of hot stamping on corrosion resistance of press hardened steel 22MnB5 metallic coated with electroplated ZnNi
2018 - COUTO, C.P.; COSTA, I.; VIVEIROS, B.G. de; ALENCAR, M.C.; PANOSSIAN, Z.; ROSSI, J.L.; COLOSIO, M.A.
The carmakers and all their production chain must achieve worldwide targets of lightweight, safety and reduced fuel consumption. The use of ultra high strength steel, such as press-hardened steels (PHS), in vehicle structures has been contributing with this. This type of steel is widely used in hot stamping process, which consists in heating the steel blank to the total austenitization temperature, and then transferring it from the furnace into the die where the steel is deformed and quenched at the same time, with a minimum cooling rate of 27 K/s. The boron-manganese PHS steel comprises perlite and ferrite microstructure, and its tensile strength is around 600 MPa in the annealed condition. Thus, after the hot stamping process the PHS microstructure completely changes to martensite and the tensile strength increases to 1500 MPa or more. The transferring step is a critical one, due to the contact of the hot steel blank with the atmospheric air; as consequence, it causes the steel oxidation. To avoid that, the steel is protected with metallic coatings. The hot-dip AlSi is the most currently used coating for this application, however, in order to keep up with the high PHS demand, alternative coatings, like zinc-base is under investigation. This work had the objective of evaluating the corrosion resistance of PHS, 22MnB5 grade, coated with electroplated ZnNi before and after hot stamping, using scanning vibrating electrode technique (SVET). The corrosion-localized techniques are more suitable, once the results showed that after hot stamping the coating layer changes completely, as a result of chemical elements diffusion. Thus, different phases of Zn-Fe-Ni are formed and random distributed which impacts the corrosion resistance of the steel.
Characterization of Al-Si coating on press hardening steel (PHS) submitted to a natural weathering test
2018 - OLIVEIRA, B.G.; CUNHA, L.F.; ABBADE, L.; COLOSIO, M.A.; ROSSI, J.L.; COUTO, C.P.; LARA, J.C.; LIMA, V.F.
Targeting the reduction of stamped sheet metal thicknesses, higher mechanical properties and better crash performance arise the hot stamping process as viable alternative. This is achieved by heating up a steel blank to approximately 900 ºC for the austenitization, soon after it is transferred to the hot stamping press, to be conformed and cooled, aiming a martensitic microstructure, After that, the finished part presents a tension strength about 1500 MPa. At the blank moving between furnace and press, oxidation occurs on the sheet metal surface, and Al-Si coating has been used as a good surface protection, which works against the oxidation process through a protection barrier. For corrosion analysis and a behavior evaluation of the coating subjected to climatic agents, the most trustful way is by means of the utilization of the natural weathering test, in the present case in an urban environment. It was used samples of 22MnB5 steel plates after different heat treatment conditions, achieving, in this way, weathering results based in technical standards obtained by means of light microscopy techniques.
A versatile setup in reflection mode for in situ diffraction patterns acquisition from flat polycrystalline specimens bathed in a liquid medium
2017 - CAREZZATO, G.L.; COUTO, C.P.; ROSSI, J.L.; MARTINEZ, L.G.; TURRILLAS, X.
A cell to perform in situ diffraction measurements of specimens regularly immersed in a liquid medium has been developed. The assembly (see Fig. 1) has been adapted to work in beamline XRD2 in reflection mode. Basically consists of a polypropylene box with two windows made of poliimide to allow the passage of X-rays (incident and diffracted) at lower angles. The flat sample is placed in the middle of the box that is on top of the goniometer head. For safety reasons the central box is positioned over a tray to avoid spillage of liquid. On the bottom of the cell there is a connection to the pipe linked to the syringe. The syringe is driven by a beamline stepping motor. This way it is easy to synchronise the filling and evacuation of liquid from the cell with the actual data acquisition of diffraction patterns. The idea is to soak the flat specimen with the liquid and then remove it to acquire the diffraction data. This can be done in a sequential way for several hours to monitor the crystalline phases present on the surface (or rather a few microns deep) of the flat specimen. Various reactions can be investigated this way, provided that the sample is flat. Ceramics, metals, and polymers in contact with liquids could be studied. Preliminary tests have been performed in two theta – theta geometry on metal plates in contact with acid solutions to simulate accelerated corrosion. However a large variety of experiments with other geometries, (grazing incidence) could be carried out and of course this assembly could be used on SIRIUS with better time resolution.
Diffusion analyses using gdoes technique of chemical elements present on 22MNB5 steel and ALSI and ZNNI coatings
2016 - COUTO, C.P.; POLITANO, R.; COSTA, P.; 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 might promote some steel oxidation. The application of coatings avoids this phenomenon. The AlSi coating, a patented process, has been the most applied on steel. Hence, alternative coatings like ZnNi are under development. It is known that this furnace heating causes chemical elements diffusion that results in intermetallics formation in the coating and in the substrate. This study has the objective of analyse the diffusion profiles of chemical elements present in the substrate and coatings of AlSi and ZnNi using glow discharge optical emission spectroscopy technique (GDOES). The results showed that the diffusion of the elements Zn and Fe is the responsible for the formation of Zn-Fe phases for those samples coated using ZnNi, besides that in the AlSi sample the diffusion of Al and Fe elements control the formation of phases which consist in Al-Fe.

CAMILA PUCCI COUTO

Projetos de Pesquisa

Unidades Organizacionais

Cargo

Filtros

Autor

Assunto

Ano de publicação

Tipo de publicação

Âmbito

Tipo de acesso

Tem arquivos

Configurações

Ordenar por

Resultados por página

Resultados de Busca