Binder Jetting of Gears: Evaluation of the Tooth Flank Load Capacity of Binder Jetting Gears Made of 17-4PH

Powder metallurgical gears are susceptible to failure due to tooth root fracture, mainly as a result of excessive bending stress. Consequently, Klee conducted research to determine the tooth bending strength of gears manufactured via Binder Jetting (Binder Jetting gears) made of 17-4PH stainless steel. Klee’s research demonstrated that the tooth bending strength of Binder Jetting gears made of 17-4PH is approximately 30% inferior to that of conventionally manufactured gears made from the same wrought steel grade. However, to establish the Binder Jetting process in gear manufacturing, it is necessary to demonstrate the performance of Binder Jetting gears in terms of both their tooth bending strength and their tooth flank load capacity. The present work investigated the tooth flank load capacity of Binder Jetting gears made of 17-4PH. Furthermore, a classification of the performance achieved by the Binder Jetting gears in comparison to gears of the same geometry conventionally manufactured from wrought 17-4PH was conducted. The evaluation of the tooth flank load capacity of Binder Jetting gears is based on the number of load cycles N achieved in back-to-back tests and the local tooth flank pressure p<inf>H</inf>. To calculate the local tooth flank pressure p<inf>H</inf>, the program tooth contact analysis (ZaKo3D) from the geartoolbox of the wzl gear research circle is used. The simulations are based on topography measurements of the tested gears to consider the load-induced deformation of the tooth flank topography. As detailed in the investigations, the number of load cycles N achieved by the Binder Jetting gears until failure due to pitting were comparable to those achieved by the reference gears. Furthermore, the calculated load cycles N<inf>50%</inf> for a failure probability of P<inf>a</inf> = 50% were N<inf>50%,BJT</inf> = 8,028,772 LC for the BJT gears and N<inf>50%,Ref</inf> = 9,505,924 LC for the reference gears and were therefore comparable. Finally, a further analysis of the experimental results was conducted to determine the local tooth flank stress (local tooth flank pressure p<inf>H</inf>) that led to the failure. It was found that the local tooth flank pressure p<inf>H</inf> of the BJT gears before pitting was lower than that of the reference gears. Thus, despite a similar number of load cycles N until failure, the BJT pinions have a lower flank load capacity.