The Effect of Chip Binding on the Parameters of the Case-Hardened Layer of Tooth Surfaces for AMS 6308 Steel Gears Processed by Thermochemical Treatment

Abstract

The following article describes influence of pressure welded or bound chips to the gear tooth flank and/or the tooth root on a carburized case and surface layer hardness of Pyrowear 53 steel gears, machined by Power Skiving method. This paper is focused only on one factor, the chips generated while forming gear teeth by power skiving, which could result in local changes in the carburized case parameters as a negatively affecting point of mechanical performance of the carburized case. The chips, due to the specifics of the power skiving process and the kinematics of tooth forming, could be subject to the phenomena of pressure welding or binding of chips to the tooth. During the carburizing stage of the downstream manufacturing processes, the chips form a diffusion barrier, which ultimately could result in localized changes in the carburized case. This work was an attempt to answer the question of how and to what extent the chips affect the case hardening. Performed simulations of chips by a generating cupper “spots”, mentioned in the study, represent a new approach in connection with minimization of errors, which could appear during carbon case depth and case hardness analysis for typical chips, generated during the machining process—assurance that a complete chip was bound to the surface. Hardness correlation for zones, where the chip appears with areas free of chips, gives simple techniques for assessment. Performed tests increased the knowledge about the critical size of the chip—1.5 mm, which could affect the case hardening. Obtained experimental test results showed that the appearance of chip phenomena on the gear tooth might have a negative impact on a carburized case depth and hardened layer.