In the present experimental study, the influence of primary martensitic structure on acceleration of graphitization process in hypereutectoid steels during subsequent heat treatment cycle was investigated by using of optical microscopy (OM) and scanning electron microscopy (SEM). Then the results have been compared with prior pearlitic and spheroidized structures. Dilatometric experimental results demonstrated the following of graphitization process from Johnson–Mehl–Avrami equation for steels with a prior martensitic structure. The Avrami exponent was determined about 1.4 that indicates a diffusion-controlled, nucleation and growth mechanism in this kind of phase transformation.

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