Study of the effect of the cementation process applied to SAE 5120 and 8620 steels on the microstructure and hardness changes

In this study, the effect of cementation process, applied to SAE 5120 and 8620 Steels, on the microstructure and hardness changes is studied. The materials chosen for the thesis study were obtained from the Hadid Makine located in Denizli, and transformed into standard experiment samples by Zirve Kalıpçılık Sanayi located in Aydın. Afterwards, the materials were subjected to the cementation process by the Isılsan Sanayi located in Izmir. The heat for SAE 5120 and SAE 8620 materials chosen as the experiment materials was fixed at 930 ºC, four different cementation durations were stated as 60 – 120 – 180 – 240 minutes and it was planned to study the behaviors exhibited by the materials during the different cementation processes. Twelve standard experiment samples were prepared for each of the experiment materials. At the laboratories of Afyon Kocatepe University Technology Faculty, those standard experiment samples, respectively; The samples prepared for the microhardness measurement were sanded with 60-80-160-240-300-600-800-1000 and 1200 grit sandpapers in turns and in the opposite directions, polished with alumina, seared with nital, photographed for the micro structures and then measured for the microhardness with Vickers hardness testing machine. As a result of the experiments of samples prepared for the Charpy Impact Test, it was observed that the toughness values of each materials were slipped as the cementation durations were extended. It was seen that the experiment sample with the longest cementation duration was the material with the least toughness. The areas where fracturing happened were sawed, subjected to the SEM monitoring at the laboratories of Afyon Kocatepe Univerisity. By studying the X500 retroreflective electron and II. Electron images, it was stated that the materials exhibited less ductile fracturing behavior as the cementation duration was extended. Therefore, it was determined that the ductility was decreased as the cementation duration was extended. The experiment samples prepared for the Tension Test were also subjected to the tension tests at the laboratories of Afyon Kocatepe University, an increase was observed at the breaking strength of the materials up to the two hour cementation duration. It was precipitated that the breaking strength of the materials subjected to the cementation process up to three hour and after showed a falling tendency.