The aim of the work was to determine the influence of the quantity and distribution of carbides on the bainitic transformation process that takes place in 90SiCrMn6-4 steel. The kinds of possible carbides that can be formed in steel and the kinetics of their precipitation were examined by the use of computer simulations. Various thermal treatments, leading to obtaining of different size and distribution of carbides in steel, were carried out. The obtained microstructures were studied by the use of Light Microscopy (LM) and by Transmission Electron Microscopy (TEM). The pre-heat-treated steel samples with different carbide size and distribution were subjected to austempering processes. The kinetics of bainitic transformation in samples with different carbide size and distribution were analysed by means of dilatometric tests and the resulting microstructures were examined by use of TEM. The obtained microstructure was composed of carbide free bainitic matrix in which carbides were observed. Thickness of the bainitic ferrite plates and austenite layers, in samples with different carbide distributions, was measured. Finally, hardness of the heat treated samples was determined.Keywords: Steel, bainitic matrix, carbide precipitations, nanostructuring process
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