Augmented multi-scale instrumented indentation test characterization of complex multi-layered coatings for tribological application

Multi-layer coatings for steel bushings consisting of an innermost layer of sintered bronze and an outermost composite layer of lead-reinforced polytetrafluoroethylene (PTFE+Pb) have been used in several power transmission applications. The PTFE+Pb layer provides lubrication by material transfer on the counter-body reducing friction and smoothing motion. The mechanical characterization of such a complex system is challenging and essential to provide input data necessary to design and predict the service life of the components. This work innovatively mechanically characterizes the coating by augmented multi-scale Instrumented Indentation Test (IIT). Nano-IIT will evaluate the uniformity of the Pb particles dispersion. Dynamic nano-IIT will investigate the damping properties of the material as a function of load frequency. Micro-IIT will tackle the layer thickness evaluation and the gradient of mechanical properties through the layers, by continuous multi-cycle and by data augmentation provided by electric contact resistance.