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Zirconia-Toughened Alumina Insert Washers for Suspension Components: Coupled Tribocorrosion-Erosion Behavior in Road-Splash Media

Zhi Yang

Journal of Ceramic Science and Technology · Early View (advance online publication) (-1), pp. 1-12

DOI: 10.4416/JCST2026-00002

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Abstract

Zirconia-toughened alumina composites with zirconia contents of 10, 20, and 30 vol% were systematically investigated as candidate insert washer materials for suspension components operating in aggressive road-splash environments. Nearly fully dense ceramics (> 99.5 %) were fabricated by means of pressureless sintering at 1 550 °C, exhibiting a progressive trade-off between hardness and fracture toughness. The incorporation of zirconia increased fracture toughness from 3.6 MPa·m1/2 for monolithic alumina to a maximum of 8.1 MPa·m1/2 at 20 vol% zirconia, while hardness decreased from 18.2 to 17.1 GPa. Tribocorrosion-erosion behavior was evaluated using a slurry jet impingement system with a simulated road-splash medium consisting of 3.5 wt% NaCl and 200 – 300 µm silica particles at a velocity of 10 m s-1 and an impingement angle of 45°. After 24 h exposure, monolithic alumina exhibited severe degradation with a cumulative volume loss of 0.86 mm³, whereas the optimized composite with 20 vol% zirconia showed the lowest loss of 0.15 mm³, corresponding to a steady-state erosion rate of 5.9 × 10-3 mm³ h-1. Electrochemical measurements revealed that mechanical damage significantly increased surface electrochemical activity for all ceramics; however, zirconia-toughened alumina maintained lower post-test corrosion current densities compared with monolithic counterparts. Post-mortem analyses demonstrated that brittle grain pull-out dominated degradation in alumina, while crack arrest and deflection associated with stress-induced tetragonal-to-monoclinic zirconia transformation governed material removal in the composites. These results identify an optimal balance of hardness and toughness that minimizes coupled mechanical and electrochemical degradation under realistic slurry impingement conditions.

Keywords

Transformation toughening, slurry jet impingement, phase stability, erosion resistance, electrochemical response

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