A study on graphitisation acceleration during annealing of martensitic hypereutectoid steel

Abstract

In this experimental study, the influence of primary martensitic structure on acceleration of graphitisation process in hypereutectoid steels during subsequent heat treatment cycle was investigated by using optical microscopy and scanning electron microscopy. Then, the results have been compared with prior pearlitic and spheroidized structures. Dilatometric experimental results demonstrated the following graphitisation 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.

Influence of Manganese Content on the Dissolution of the Iron Carbide Phase (Cementite) during a Graphitization Anneal of Spheroidal Graphite Cast Iron

“…In conclusion, all the results confirm that the kinetics of graphitization of the cementite is further slowed when the melt is rich in manganese, while, also, recent studies show that the structure of the matrix can play a role in this development [5].…”