Rodrigo Leonardo de Oliveira Basso

Magnetic and structural properties of ion nitrided stainless steel

The magnetic properties and crystalline structure of expanded austenite obtained by ion beam nitriding of AISI 316 steel are investigated. Magnetic force microscopy reveals that the nitrogen expanded austenite has two different layers, an outermost ferromagnetic layer and a paramagnetic layer beneath it. Superimposing the nitrogen concentration profile determined by secondary neutral mass spectrometry and the magnetic force microscopy image, one can see that the paramagnetic-ferromagnetic transition takes place at the inflection point of the nitrogen concentration profile at about 14±2 N at. %. Conventional and glancing angle x-ray diffraction suggests that nitrogen could occupy first tetrahedral interstitial positions (nitrogen-poor paramagnetic phase) and then, after saturation of Cr traps, octahedral interstitial positions (nitrogen-rich ferromagnetic phase). The ferromagnetic-paramagnetic transition is seen to be governed by Cr (traps)–N interactions.

Effect of Carbon on the Compound Layer Properties of AISI H13 Tool Steel in Pulsed Plasma Nitrocarburizing

Due to the mechanical and inertness properties of the e-Fe2-3N phase, its formation as a compact monolayer is most wanted in plasma surface treatments of steels. This phase can be obtained by the inclusion of carbon species in the plasma. In this work, we present a systematic study of the carbon influence on the compound layer in an AISI H13 tool steel by pulsed plasma nitrocarburizing process with different gaseous ratios (0% ≤ [CH4]/[N2 + CH4 + H2] ≤ 4%). The plasma treatment was carried out for 5 h at 575 °C. The microstructure and phase composition of the modified layers were studied by scanning electron microscopy and X-ray diffraction, respectively. X-Ray photoelectron spectroscopy was used to measure the relative concentration of carbon and nitrogen on the surface. The hardening profile induced by the nitrocarburized process is also reported.

SÍNTESE E CARACTERIZAÇÃO DE FILMES FINOS DE ZrN DEPOSITADOS EM DIFERENTES TEMPERATURAS

Zirconium nitride (ZrN) nanometric films were deposited onto different substrates, in order to study the surface crystalline microstructure and also to investigate the electrochemical behavior to obtain a better composition that minimizes corrosion reactions. The coatings were produced by physical vapor deposition (PVD). The influence of the nitrogen partial pressure, deposition time and temperature over the surface properties is studied. Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques and corrosion experiments were performed to characterize the ZrN hard coatings. As expected, the ZrN films properties and microstructure changes according to the deposition parameters. The corrosion resistance increases with the temperature used in the films deposition. Corrosion tests show that ZrN coatings deposited by PVD onto titanium substrate can improve the corrosion resistance.