Characterisation of ZrO2 layers deposited on Al2O3 coating

The paper describes a method of coating combining two different layer types. The first layer is Al2O3 produced by plasma spraying with a thickness of around 200 μm which was deposited on a stainless steel substrate. Subsequently, ZrO2 layers were deposited on to the Al2O3 coating by a sol–gel process using a dip coating technique. The dip coating process was repeated in order to see the influence of the number of ZrO2 layers. Moreover, the effect of annealing temperature was investigated. In order to study their tribological behaviour, the coatings were subjected to micro-scale abrasion, scratch testing and ball-on-disc tests. The result shows that sol–gel ZrO2 top layers reduce friction and enhance the wear resistance of the coating system.