O estudo dos efeitos de tratamento térmico na microestrutura e nas propriedades mecânicas de aços maraging modificados com Nb e Ti.

Abstract

Modified maraging steels are excellent candidates for optimizing the ultra-strength properties already known in these materials. In addition to combining the characteristics associated with the FeNi18% alloy, the addition of other alloying elements can improve the properties of this material. Therefore, understanding the microstructural behaviour and its mechanical properties is necessary through understanding the real influences of the content of these elements in different heat treatment conditions commonly applied to these materials. Thus, three maraging steel alloys were investigated by varying the titanium and niobium content and subjected to different solution annealing temperatures followed by aging. Using X-ray diffraction techniques, hardness tests, optical and scanning electron microscopy/EBSD, it was possible to identify the phases present in the samples and evaluate their characteristics according to different levels of heat treatment. Therefore, the analysis showed that the solution annealing treatment does not significantly influence the hardness values, despite the samples with Ti being slightly superior when aged. The steels presented a completely martensitic microstructure that varied in grain size according to the solution annealing temperature. Samples with Ti had the largest grain sizes, highlighting niobium as a refining agent for these alloys. Furthermore, some retained austenite peaks were detected at critical solution annealing temperatures for niobium-containing samples.