Determinação de ataques químicos para revelação de estrutura martensítica em aços baixo carbono

Abstract

Carbon steels have several applications, and for each one there are specific requirements for properties that are achieved through microstructural control. For this, they are subjected to thermal treatments such as quenching, which is quite common, in which the material acquires greater hardness through the formation of martensite, which can weaken the material and cause component failure. Thus, followed by quenching, the tempering heat treatment is carried out to relieve the stresses resulting from the hardening of the material, increasing its ductility and toughness. However, even after tempering, it is possible to still have untempered martensite, which can be detected by microstructural analysis, applying microscopy techniques. From this, this work focused on the use of different reagents to analyze the microstructure of carbon steel for the presence of martensite. The low carbon steel samples were cut, embedded, sanded and polished, followed by chemical etching to reveal their microstructure. The reagents used were Nital 2%, LePera and modified LePera. From the analyzes carried out using an optical microscope, it was concluded that the result depends on the percentage of elements contained in the steel, and, in the presence of elements of greater hardenability, Nital 2% presents better results, while LePera presents better results when the reactivity between its elements and those of steel is greater. The modified LePera showed less clarity in revealing the microstructure.