Spur gear teeth reconstruction via direct laser deposition

Fatigue damage, such as pitting and tooth root fatigue fracture, is one of several gear failure modes encountered in practical applications. Some of these failure modes are traditionally repairable, while others are known to be catastrophic and unrepairable. Direct Laser Deposition (DLD) is a Metal Additive Manufacturing process that could overcome this problem and extend the useful gear life. The DLD repair process proved to be applicable in several cases. Nevertheless, concrete applications for gears are still scarce and limited to preset teeth reconstruction without discussing functional applications. Based on that perspective, this research aims to evaluate the DLD performance of a gear under actual operation. This work details the strategy applied to restore a base material case-hardened 16 MnCr 5 FZG‑C Type C-GF pinion using a DLD combination of pure Inconel 625 (MetcoClad 625) for the tooth core and pure AISI 431 (Metco 42C) as a superficial coating. The pinion was tested for over 2.7 million cycles under different load stages (K1 to K9), functionally resisting until a static torque of 215.6 Nm, although it presented severe surface damage development throughout the campaign. This exploratory work thoroughly discusses the drawbacks encountered in the repair process, materials characterization, surface evolution of the restored teeth against base material, and mass loss during the tests.