Preparation and properties of sol-gel Al2O3 coating on carbon steel

The alumina ceramic coating was prepared on 45 steel substrate by sol-gel process. The influence of electroless Ni-P plating film as an intermediate layer of Al2O3 ceramic coatings and 45 steel substrate on propecties of the coating was studied. The bond strength of the alumina coating with 45 steel substrate was investigated by indentation method and scratch test. The morphology of indentation and scratch was observed by optical microscope (OM). The surface morphology of alumina coating was characterized by scanning electron microscopy (SEM). The results show that the alumina ceramic coating is uniform. Good metallurgical bonding between the Al2O3 layer, intermediate layer and the substrate materials can be obtained. The maximum microhardness of the coating is 1030 HV. The alumina ceramic coating has good bond strength with 45 steel substrate.