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This paper focuses on the tribological behaviour of ZrN/ZrCN coating on bearing steel substrates DIN 17230, 100Cr6/1.3505. Coatings are applied at room temperature processes by means of Cathodic Arc Evaporation (CAE), a kind of Physical Vapor Deposition (PVD) technique. In order to achieve a satisfactory compromise between coating-substrate adhesion and the surface roughness requirement of the bearing rings, a polish post-processing is proposed. Different polish post-processing times and conditions are applied. The coated and polished bearing rings are tested under real friction torque test protocols. These tests show that the application of the coating does not entail a significant improvement in friction performance of the bearing. However, fatigue tests in real test bench are pending to evaluate the possible improvement in bearing life time.

A systematic study comparing the wear behaviour of composites with nylon matrix (PA66, PA46, PA12) and different nanoadditives and reinforcing additives (graphite, graphene, MoS2 and ZrO2) has been carried out in order to achieve a proper self-lubricant material for bearing cages. The wear characterisation was done using pin-on-disc tests, SEM and EDX analysis. The results show that better outcomes are obtained for composites based on PA12. The addition of ZrO2 offers negative values of wear due to the metallic particle transference from the counterface to the polymeric pin.

This paper focuses on tribological behavior of ZrCN coating on bearing steel substrates DIN 17230, 100Cr6/1.3505, fulfilling also roughness and adherence requirements. Two strategies are followed to achieve a reduction of coefficient of friction. Initially, a low roughness coating by using physical vapor deposition (PVD sputtering process) is developed. At this stage, PVD conditions guarantying adherence and avoiding drops generated during that process are achieved. A second strategy consisting of application of several polish post-processes is proposed. These polish post-processes pretend to reduce roughness keeping, at the same time, a proper adherence. Different post-process durations and conditions are analyzed to achieve positive adherence results. Coated bearing samples obtained from the application of these two strategies are tested in friction test rigs. These tests conclude that there is not a significant improvement friction performance by applying ZrCN coatings compared to bearing baseline.