Estudo comparativo do tratamento térmico intercrítico no aço SAE 8620 em três tempos distintos

Abstract

To study the microstructure evolution of a SAE 8620 steel heat treated at 740°C, its intercritical zone, 4 samples were produced and 3 heat treatments of distinct durations, 30 minutes, 2 hours, and 6 hours, were realized, followed by water quenching. The samples were characterized,using light microscopy and microhardness testing, aiming to compare their microstructures and their hardness properties. The martensite in the sample treated for 30 minutes underwent a decomposition, decreasing its hardness. There was a completeaustenitization of the β phase on the sample treated for 2 hours producing a well succeeded hardening. Decarburization occurred on the sample treated with 6 hours, which showed amicrostructure of ferritic matrix with martensite isles. It was concluded that the 2-hoursintercritical heat treatment followed by quench generates a microstructure of ferrite and martensite on a SAE 8620 steel, and that the 6-hours heat treatment can result in decarburizing.