Navegando por Autor "Rodrigues, José de Anchieta"
Agora exibindo 1 - 2 de 2
- Resultados por página
- Opções de Ordenação
Artigo Growth of nitrided layers on Fe–Cr alloys(Elsevier, 2000-02-29) Alves Júnior, Clodomiro; Rodrigues, José de Anchieta; Martinelli, Antonio EduardoChromium is an important alloying element present in numerous commercial steels. A systematic study on the nitriding behavior of Fe–Cr alloys is helpful in predicting the properties of nitrided Cr-alloyed steels. Aspects such as microstructural evolution, growth kinetics, and mechanical properties should be particularly emphasized. Fe–Cr alloys containing 5, 10, and 20 wt.% Cr have been arc melted and subsequently plasma nitrided under a N2–80% H2 atmosphere. The microstructure of the resulting nitrided layers was characterized and the microhardness profiles evaluated. Thicker layers developed on low chromium alloys. Differences in hardness profiles were also observed as a function of chromium contents. Nitriding Fe–5% Cr alloys resulted in two discrete fronts, refereed to as the diffusion front and the transformation front. Transformed regions sustained a decrease in hardness from 1000 down to 600 HV, associated with the conversion of homogeneously dispersed fine precipitates into coarser needle like particles immersed in the ferritic matrix. Similar behavior was not observed for the other alloys, where both fronts developed simultaneouslyArtigo The effect of pulse width on the microstructure of d.c.-plasma-nitrided layers(Elsevier, 1999-12-15) Alves Júnior, Clodomiro; Rodrigues, José de Anchieta; Martinelli, Antonio EduardoModern ion nitriding equipment are powered by pulsed sources in order to prevent arcing and overheating. In industrial applications, the pulse frequency is usually adjusted to set the working temperature. However, frequency variations may drastically affect the plasma species population, and consequently, the microstructure of the final nitrided layer. In this study, AISI-409 steel was nitrided in a mixture of 20% N2–80% H2 using a d.c power source. The depth and microstructure of the nitrided layer were assessed as a function of the time that the voltage was off, toff, in the range of 1–4 ms during a 10 ms pulse cycle. The results suggested that both the microstructure and mechanical behavior of the nitrided layer were affected by toff. Long toff values imply a deleterious effect on the mechanical properties of the nitrided layers