Rolling Contact Fatigue of Alumina Ceramics Sprayed Roller

The rolling contact fatigue of a sprayed alumina ceramics with a nominal composition of Al2O3-2.3 mass%TiOz was studied with a two-roller test apparatus under pure rolling contact condition with oil lubricant. The alumina ceramics was prepared by plasma spray process. The influence of undercoating of sprayed Ni based alloy and surface sealing on the rolling contact fatigue was investigated. The failure mode of all sprayed rollers was spalling caused by subsurface cracking. Neither undercoating nor surface sealing contributed to the improvement of the rolling contact fatigue. The elastic modulus of the alumina sprayed layer evaluated with the nano-indentation method was around 85 GPa. The subsurface shear stresses were calculated with two-dimensional FEM analyses. The maximum values of orthogonal shear stress and maximum shear stress occurred within the sprayed layer. The depths of observed subsurface cracks were generally deeper than those of the maxima of shear stresses.