1144 Journal of the American Ceramic Society--Zhang et al. Vol. 90. No. 4 5432 0 67 200ur Energy /kev Scanning electron micrograph and EDS spectra of wear debris of self-mated C/SiC composites tested under a load of 3.5 kN and a constant g velocity change was obtained after tested at 1. 3.5. and 5 kN. The main Wear mechanisms of ceramics are predominantly dependent difference was that the surface became more compact and on the tribological contact stresses. At low contact stress, the mother with increasing load. The degree of damage of the removal of material is controlled by plastic deformation-induced urface caused by the groove is mainly dependent on the sliding microfracture on the asperity contact scale. Wear debris are peed and applied load(contact pressure)on the friction surface. produced when the plastic deformation exceeds the plasticity No obvious adhesion phenomena and no peeling occurred on limit of the material. Based on the analysis, the wear between the contact surfaces. No cracks were found on the rotating axle self-mated C/Sic composites did not shift to the severe adhesion after tests under a load of I kN. However, several shallow cracks stage, and still remained in the grain abrasion stage with a mild were observed after tests at a load above 3.5 kn as shown in vear under a high load and a low sliding velocity. The wear Fig. Il. The local high temperature between the contact surfaces debris that remained in the wear track was ground to a very fine during the friction generally plays an important role in the de- powder by continuous rubbing. The smooth and compact tribo- formation of cracks on the surface, especially on the surface that layer formed on the contact surface exhibited several shallow is a coating on the substrate. Sometimes the mismatch of TEcs cracks under a load above 3. 5 kN. the grain abrasion wear is between the coating and the substrate is the main reason for the main wear mechanism of the self-mated C/SiC composite formation of cracks hinge bearing within the framework of the testing conditions 50 um 50 um 50 um Fig 10. Con sliding velocichange was obtained after tested at 1, 3.5, and 5 kN. The main difference was that the surface became more compact and smoother with increasing load. The degree of damage of the surface caused by the groove is mainly dependent on the sliding speed and applied load (contact pressure) on the friction surface. No obvious adhesion phenomena and no peeling occurred on the contact surfaces. No cracks were found on the rotating axle after tests under a load of 1 kN. However, several shallow cracks were observed after tests at a load above 3.5 kN as shown in Fig. 11. The local high temperature between the contact surfaces during the friction generally plays an important role in the de￾formation of cracks on the surface, especially on the surface that is a coating on the substrate. Sometimes, the mismatch of TECs between the coating and the substrate is the main reason for formation of cracks. Wear mechanisms of ceramics are predominantly dependent on the tribological contact stresses. At low contact stress, the removal of material is controlled by plastic deformation-induced microfracture on the asperity contact scale. Wear debris are produced when the plastic deformation exceeds the plasticity limit of the material.14 Based on the analysis, the wear between self-mated C/SiC composites did not shift to the severe adhesion stage, and still remained in the grain abrasion stage with a mild wear under a high load and a low sliding velocity. The wear debris that remained in the wear track was ground to a very fine powder by continuous rubbing. The smooth and compact tribo￾layer formed on the contact surface exhibited several shallow cracks under a load above 3.5 kN. The grain abrasion wear is the main wear mechanism of the self-mated C/SiC composite hinge bearing within the framework of the testing conditions. Fig. 10. Contact surfaces of a carbon fiber reinforced silicon carbide matrix (C/SiC) axle before and after friction against a C/SiC ring under constant sliding velocity of 33 10
3 m/s and a load of 1 kN. (a) As-machined surface on the axle before the tests; (b), (c), and (d) contact surfaces of testing positions a, b, and c on the axle after the tests. Fig. 9. Scanning electron micrograph and EDS spectra of wear debris of self-mated C/SiC composites tested under a load of 3.5 kN and a constant sliding velocity of 33 10
3 m/s. 1144 Journal of the American Ceramic Society—Zhang et al. Vol. 90, No. 4