Influence of Time and Temperature on Decarburization Rates for AISI 52100 and 1095 High Carbon Steel

Decarburization of steel parts during annealing results in a lower surface hardness after heat treatment. Significant efforts have been made towards preventing decarburization, as well as understanding the relationship between annealing time, temperature, and decarburization rate. However, much of the research has placed emphasis on steels with lower carbon content, ranging from 0.3 weight percent up to the eutectoid point. The goal of this research is to investigate the phenomena surrounding decarburization of steels with carbon concentrations above the eutectoid concentration. 1095 plain carbon steel was decarburized for different times (12, 24, and 36 hours) in three temperature ranges, below Ac₁, above Ac_cm, and between Ac₁ and Ac_cm. 52100 alloy steel was decarburized for the same times in two temperature ranges, below Ac₁ and between Ac₁ and Ac_cm. Hardness traverses for samples heated above Ac_cm were taken to determine decarburization depth. Optical and Scanning Electron Microscopy were used to determine the carbon concentration as a function of depth from the surface. This information was then used to determine the diffusion coefficients of carbon in iron. These diffusion coefficients can be used in a finite difference simulation to predict decarburization at different temperatures and times.