Friction and Wear Experiment and Simulation of YSZ-CaF2 Coating at High-temperature Conditions
Aero-engine thrust-to-weight ratios and inlet temperatures continue to rise, imposing severe tribological demands on high-temperature moving components. YSZ-CaF2 self-lubricating wear-resistant coatings were deposited by plasma spraying, and ball-on-surface reciprocating sliding tests were conducted from room temperature to 800 °C. Friction coefficient and wear rate both decreased monotonically with increasing temperature, reaching minima at 800 °C. Post-test characterization by SEM/EDS, XRD, and white-light interferometry revealed increased surface concentrations of ZrO2 and Al2O3 wear-resistant phases and CaF2 lubricious phase, accompanied by formation of a continuous protective oxide layer. A finite element model of the ball/coating contact incorporating thermomechanical coupling was developed, and a wear simulation method integrating temperature-dependent friction coefficients and wear rates was implemented using Archard wear theory and Arbitrary Lagrangian-Eulerian adaptive meshing. Simulated contact pressures agreed with Hertzian analytical solutions, and simulated wear volumes deviated from experimental measurements by less than 3% at all tested temperatures. The simulations further showed that contact pressure decreased and became more uniformly distributed as temperature increased. The combination of increased CaF2 lubricious phase and ZrO2/Al2O3 wear-resistant phases, together with oxide layer formation, improved interfacial contact conditions and reduced friction and wear. The proposed simulation methodology is validated as accurate and effective for predicting tribological behavior and wear evolution of YSZ-CaF2 coatings under high-temperature service conditions.