A Study of Wear in Thin Coatings Applied to Convex-Concave Gearings

The submitted contribution deals with the wear of thin coatings applied to convex-concave gearings for gear made from C45E steel. The influence of the tribological characteristics (friction coefficient, wear, adhesion and hardness) of the TiN, TiCN coatings and the combined coating of TiCN + MoS2 on convex-concave gearing is described, from the aspects of scuffing formation. Scuffing tests were done on C-C gears. Coatings were applied by arc-ion-plating (AIP) and magnetron sputter-ion-plating (MSIP) methods. The thickness of the deposited coating and its chemical composition were determined by SEM and EDX analysis. Load-bearing capacity was evaluated by a Niemann tester. The TiCN + MoS2 combined coating with the MoS2 layer on the top reached the lowest coefficient of friction. However, after a rapid wearing of the MoS2 layer, this value dropped to a comparable value of TiCN. The nano-hardness of the TiCN layer was higher in comparison with TiN. Thin and soft MoS2 layers cracked already at lower load levels and separated from the substrate at the 5th load stage. The formation of scuffings for selected coatings documented in this article was solved for convex-concave gearing working also in interaction with Biogear S 150 and Biohyd MS 46 oils.