Failure analysis of S50C carbon steel applied for fine boring transmission system

Abstract

The purpose of this research was to analyze the failure of the axle of fine boring transmission system shaft engine which was subjected to JIS G4051 S50C carbon steel. In industrial machinery, fatigue failure is often found on the work machine. The transmission system uses a bearing on each side of the shaft so that the shaft rotation becomes smoother and the shock load at the beginning of the rotation becomes smaller. This analysis was carry out by comparison of metallographic results such as fractography by SEM, identification of chemical composition by OES, mechanical properties by tensile and Rockwell test with loading 150 kgf, and calculation of fracture toughness. The analysis obtained from the research showed that, the average of fracture toughness evaluated by hardness and tensile crack were 26 and 77 MPa.m1/2, respectively. Therefore, by fracture toughness calculation results and crack propagation in microstructure results, it is confirmed that that the shaft does not meet the JIS Key Slot standard, and these factors would contribute to the occurrence of failures on the transmission shaft.