Residual stresses and their effect on wear behavior of polycrystalline zirconia overcoated disks

Scanning and transmission electron microscopy studies were conducted to investigate the wear behavior of unlubricated polycrystalline zirconia-overcoated disks. The results indicate that the overcoat is susceptible to cracking in the direction of sliding. Cracking in the zirconia-overcoated disks appears to initiate at triple points and propagates along the grain boundaries. The tendency to crack formation appears to be related to the presence of a residual stress in the sputtered overcoat and also to nanometer-scale porosity at the grain boundaries. Preliminary X-ray diffraction investigations suggest that a compressive residual stress of about 3.5 GPa is present in the overcoat.<
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