Tribological Properties and Wear Mechanism of Phenolic Resin Incorporated Rare Earth Oxides

Different proportions of rare earth oxides, specifically cerium oxide and yttrium oxide, were incorporated into phenolic resin-based friction materials to mitigate the thermal degradation of resin-based friction materials. The effects of these additives on the mechanical properties and tribological performance of resin-based friction materials were thoroughly investigated, and the microstructure and phase composition were characterized via field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The addition of rare earth oxides favorably improved the density, hardness, compression strength, and shear strength of the composites, with rare earth yttrium oxide dominating the hardness of the composites and cerium oxide dominating the compression strength of the composites, but changes in the ratio of the two had a small effect on their density, shear strength, and impact strength. Among them, the highest density, hardness, compressive strength, and shear strength of the modified sample could reach 2.310 g/cm3, 118 HRL, 187.5 MPa, and 43.5 MPa, respectively, and their properties were improved by 7.7%, 14.6%, 19%, and 51%, respectively, compared with the unmodified sample Y0. The incorporation of rare earth oxides was not conducive to the improvement of the fade friction coefficient and recovery friction coefficient of the composites, but was beneficial to the stabilization of the recovery friction coefficient of the composites and the reduction in their average wear rate, with the yttrium oxide-dominated matched samples focusing on high-temperature stability, and cerium oxide-dominated matched samples focusing on the antioxidant reduction property. The homogeneous dispersion and synergistic enhancement effect of the rare earth oxides in the matrix materials enhanced the structural integrity and densification of the matrix materials and improved the interfacial strength and surface wear resistance of the composites. The worn surface of the unmodified sample Y0 was mainly abrasive and thermal fatigue wear, the worn surface of the yttrium oxide-dominated matched samples Y1 and Y2 was mainly abrasive wear, and the worn surface of the cerium oxide-dominated matched samples Y3 and Y4 was mainly adhesive and thermal fatigue wear.