Semi-interpenetrating network composites containing 40 vol% ceramics (5Al2O3.8SiO2) and 60 vol% Al-alloy were fabricated in place of cast iron available for automotive brake rotors. The friction and wear performances of brake pads dry sliding against the composites were measured using a SRV (vibration-frictional wear (Schwingungs-Reibverschleiss)) testing machine. The test procedures include friction fade and recovery, load sensitivity at 100 deg C and 250 deg C, and wear. The friction was found to increase first and then decrease with increasing temperature, followed by the inverse recovery upon cooling. Wear showed an incremental tendency over a wide temperature range. For loads from 40 N to 160 N, the friction decreased at 100 deg C and 250 deg C. At load below 128 N, the former friction was inferior to the latter while at load above 128 N the friction exhibited an inverse tendency. Wear mildly increased with load at 100 deg C and decreased dramatically at 250 deg C. SEM (scanning electron microscopy) and EDS (energy-dispersive spectroscopy) investigations revealed that the worn pad surfaces at 250 deg C were covered by more tribofilms, including more coke and graphite with friction-reducing action as well as fewer compounds (corresponding to Si and Al) with friction-increasing action in comparison with those at 100 deg C. The compression of the tribofilms contributed to a large decrease in the friction and wear with increasing load. However, at 100 deg C E-glass fibres (electric glass fibres) exposed at the worn surfaces inhibited the excessive wear of the pad despite lack of more tribofilms. Their glossy surfaces decreased the friction. The proposed friction models explain some friction and wear behaviour better.
Friction and wear behaviour of brake pads dry sliding against semi-interpenetrating network ceramics/Al-alloy composites
Tribology Letters ; 38 , 2 ; 135-146
2010
12 Seiten, 13 Bilder, 1 Tabelle, 10 Quellen
Article (Journal)
English
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