Improvement of fatique properties of the gears in planet reductors

In this study, production of the gears as-cast, rolled and forged (roll+forge) forms and their associated fatique properties have been investigated. Machining of gear teeths has been has been carried out from the rolled and forged billets. Sementation processing has also been applied to the produced gear teeths. Microstructral investigatons were carried out by using optical microscopy. Hardness and tensile tests were applied to the produced samples. Their fatique properties were evaluated by using three-point bending tests under the repeated loadings. Additionally, SEM analysis were used for the investigation of the ruptured surfaces. Approximately 80% of the tensile strengths were applied as the applied loads for the fatique tests. Results showed that both ductility and fatique strenghts of the 8620 steel were improved considerably after the forging. Tensile test samples produced by rolled billets were ruptured at 23.500N whereas the rupture was took place at 43.000N for the forged samples. Fatique strengths of the samples produced form rolled billets raptured after the 12 repeats while the forged samples ruptured after 85 repeats. Keywords: Planet gear systems, Fatique, AISI 8620