Influence of Time and Temperature on Decarburization Rates for AISI 52100 Steel

Decarburization of steel parts during heat treating results in a lower surface hardness, undesirable residual stress profiles, and poor part performance. Significant effort has been made towards preventing decarburization and determining the impact of annealing time and temperature on decarburization rate. Much of the published research has focused on medium carbon steels, ranging from 0.3wt% C to the eutectoid composition. The goal of the current research is to determine decarburization rates for steels with carbon concentrations above the eutectoid concentration. AISI 52100 steel was heated in air for 12, 24, and 36 hours at three temperature ranges (below A₁, above A_cm, and between A₁ and A_cm). Optical microscopy was used to determine the carbon concentration as a function of depth from the surface. The diffusion coefficients of carbon in austenite and ferrite plus cementite phase assemblages were calculated. These diffusion coefficients can be used in a finite difference simulation to predict decarburization at different temperatures and times.