Wear Behavior of AISI 8620 Steel Modified by a Pulse-Plasma Technique

Abstract

In this study, the micro-hardness, wear behavior, and microstructure of AISI 8620 steel, which was initially annealed at 700 degrees C and carburized for 2 h at 900 degrees C, were studied before and after pulse-plasma treatment. The surfaces of the samples were modified by a mixture of nitrogen, C(3)H(8), and oxygen gases by using a pulse-plasma technique. Two different battery capacities of 800 and 1000 mu F and two different sample plasma gun nozzle distances of 60 and 80 mm were chosen for surface modification. Microhardness measurements were carried out on the sections perpendicular to the surfaces treated and hardness profiles from the outer surface to the inner sections of the samples modified by pulse-plasma were determined. The measurements showed that pulse-plasma treatment resulted in a remarkable increase in surface hardness of an AISI 8620 steel after the conventional carburizing process and the maximum hardness value measured was as high as HV910. Ball-on-disc wear tests according to ASTM G99 were also conducted on the treated samples of AISI 8620 steels in order to investigate their wear and friction performance in dry sliding conditions. Worn surfaces were analyzed and dominant wear mechanisms were identified using the SEM and EDS techniques. It was found that the pulse-plasma treatment considerably improved the wear resistance of all treated materials. However, it was shown that the process parameters as well as the initial heat treatment had a profound effect on the wear rate and the maximum wear resistance was obtained from those initially subjected to heat treatment and then treated by pulse-plasma at the battery capacity of 800 mu F and nozzle distance of 80 mm.