Development of Case-Carburized Gear for the High Load-Carrying Capacity : Changes of Rolling-Sliding Contact Surface under the High Load Condition

Since the manufacturing methods of gears were improved, the failure of case-carburized gears has changed to the surface fatigue of the tooth flank from the fatigue breakage at the tooth fillet. The objective of this work is to develop the case-carburized gears for the high load-carrying capacity. Then, the factors of influence on the surface durability of the hypoxia vacuum melting case-carburized alloy steel were investigated by using a backup-roller-type two-roller fatigue test rig. As a result of examining the rolling-sliding contact surface of the test roller under the high load condition. the following were clarified :(1)The surface failure with various features occurs. (2) The surface temperature rises above tempering temperature of heat treatment process. (3) The surface asperities become very smooth. (4) The surface profiles are greatly deformed. (5) The surface hardness decreases. In addition, (6) The outside diameter of the test roller increases.