Determination of isothermal Austenite Grain Growth model parameters for SAE 8620H Carburizing steel

Yıldız, Seçil
Yılmaz, Hasan
Yazır, Büşra
Evcil, Eilf
Şimşir, Caner
Davut, Kemal
Carburizing treatments involve longer holdings at the austenite region, which can produce a range of different prior-austenite grain sizes (PAGS) depending on the growth behavior. The PAGS influences hardenability, phase transformation kinetics and hence the final phase fraction; and therefore the final mechanical properties. Since the high-temperature austenite structure is transformed during subsequent cooling steps, controlling the formation of desired austenitic structure during carburizing treatment is difficult and particularly important. This study aims at predicting the PAGS during carburizing by using a model based on ideal grain growth law. In order to construct the validity of the model, SAE 8620H steel samples were austenitized at 3 different temperatures (850o C, 900o C, 925o C) for 3 different durations (15 min, 8 h, 24h), and then cooled at a rate of 350o C/s to ensure transformation to martensite. The PAGS of those samples were determined by metallographic examination using optical microscope. The PAGS were then determined by Heyn Intercept Method, performed on at least 5 micrographs per specimen. The results show that the grain growth behavior of the present 8620H steel can be explained by ideal grain growth law. The model parameters determined from the present experimental results agree reasonably well with the other studies on same steel grade.
Citation Formats
S. Yıldız, H. Yılmaz, B. Yazır, E. Evcil, C. Şimşir, and K. Davut, “Determination of isothermal Austenite Grain Growth model parameters for SAE 8620H Carburizing steel,” Istanbul, Turkey, 2016, p. 485, Accessed: 00, 2021. [Online]. Available: