Influence of sprayed layer thickness on rolling contact fatigue of ceramics sprayed roller

The influence of the sprayed layer thickness on the rolling contact fatigue of a thermally sprayed alumina ceramics with a nominal composition of Al₂O₃-2.3 mass%TiO₂ was investigated using a two-roller test machine under pure rolling contact condition with oil lubricant. The influence of undercoating of sprayed nickel based alloy on the rolling contact fatigue was also investigated. The thicknesses of the ceramics sprayed layer of the test rollers were 0.2. 0.5 and 1.0mm. The failure mode of the sprayed rollers was spalling caused by subsurface cracking. In case of the sprayed rollers without undercoating, the rolling contact fatigue strength of the rollers with 0.2 mm thickness sprayed layer was the smallest. The rolling contact fatigue strength of the sprayed roller with 0.2 mm thickness alumina sprayed layer was improved by undercoating. In case that the failure depth was small as compared with the thickness of the sprayed layer, the effect of undercoating on the rolling contact fatigue strength was little. The depths, where the maximum values of subsurface shear stresses occurred, almost corresponded to the observed depths of spalling cracks.