Microstructural Contact Mechanics Finite Element Modeling Used to Study the Effect of Coating Induced Residual Stresses on Bearing Failure Mechanisms

Coatings have the potential to improve bearing tribological performance. However, every coating application process and material combination may create different residual stresses and coating microstructures, and their effect on bearing fatigue and wear performance is unclear. The aim of this work is to investigate coating induced residual stress effects on bearing failure indicators using a microstructural contact mechanics (MSCM) finite element (FE) model. The MSCM FE model consists of a two-dimensional FE model of a coated bearing surface under sliding contact where individual grains are represented by FE domains. Interactions between FE domains are represented using contact element pairs. Unique to this layered rolling contact FE model is the use of polycrystalline material models to represent realistic bearing and coating microstructural behavior. The MSCM FE model was compared to a second non-microstructural contact mechanics (non-MSCM) model. Results show tensile residual stresses induced by the coating have a negative impact on the bearing performance indicated by the increase in subsurface localized plastic strains. The non-MSCM models predict higher amounts of plastic strain in relation to the MSCM models. One of the key benefits of the MSCM model over the non-MSCM model is the ability to predict crack growth and gap distance. The MSCM models show an increase coating crack gap distances due to tensile coating residual stresses. A detailed discussion of these results and the overall value of the developed model's methods and considerations are presented in this work. © 2014 SAE International.