Advanced Materials Research Vol. 68

Abstract: In recent years the use of ceramic coatings to reduce metallic corrosion has been greatly improved. It has been proved by several studies that coating of TiO2, ZrO2, SiO2, and other oxides or mixed oxides provide efficient protection against the corrosion of stainless steel in different media. In this work, alumina and zirconia films were obtained by electrophoretic deposition to investigate their use as protective coatings of 316L-Stainless steel for prostheses and dental implants. These were characterized by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GID), and atomic force microscopy (AFM). The corrosion behaviour in Hank’s solution at room temperature was studied using a potentiodynamic polarization technique. The electrochemical measurements showed a high corrosion resistance of 316L-SS coated by both types of ceramic film. The best behaviour was presented by the alumina coating. The morphologies of the corroded films showed that the alumina and zirconia films presented low damage with little pitting corrosion compared with the uncoated 316L-SS.

Abstract: Galvannealed coatings are obtained by heat treating galvanized steel strips and are widely used in the automotive industry due to their improved properties. The variables influencing coating formation on high strength low alloy steel (HSLA) were analyzed. The study was carried out on samples obtained from an industrial plant and on samples coated in a hot dip process simulator. The mechanical properties of the steel substrate were evaluated, and the morphology and Fe content in the various phases of the coating and its characteristics were analyzed and compared. It was found that the Fe-Zn phases can be controlled and performed varying the temperature and holding time during the annealing cycles, avoiding the formation of undesirable phases.

Abstract: A series of linear and spot stir welding friction tests were carried out on aluminum samples of 1 mm in thickness and area of 100 mm x 27 mm. The tool rotating speed was varied from 2000 to 4000 RPM and the feeding rate from 45 to 67.8 mm/min. The temperature distribution during welding was measured by thermocouples inserted within the aluminum strips. The microstructure of the welded nuggets and the HAZ were analyzed by optical and scanning electron microscopy. Some samples were tested intension to measure the load carrying capacity of the welded bead. Preliminary analyses indicate that the temperature at the heat affected zone increases with the rotating speed.

Abstract: The second derivative of the remission function of several magnetic materials is calculated for the parameterization of the position and intensity of the absorption bands of diffuse reflectance spectroscopy. The reflectance spectra are obtained by ultraviolet-visible spectroscopy (UV-VIS) from 400 to 1100 nm at increments of 1nm. The noise of the remission function results on errors after calculating the second derivative. Therefore, filtering of the remission function is needed before taking any action on this signal. Several methods are tested in order to calculate the second derivative. The best polynomial resulted on a second order wavelet function which is applied to the filtered remission function. Light scattering Mie theory is used to prove the behaviour of the reflected light. This research provides a method to identify and quantify magnetic particles, as well as the crystal size.