Alumina coatings obtained by thermal spraying and plasma anodising — A comparison

Abstract

Thermally sprayed alumina coatings are widely used in a range of industrial applications to improve wear and erosion resistance, corrosion protection and thermal insulation of metallic surfaces. These properties are required for many components to be used for production processes in the paper and printing industry.Another appropriate method to produce ceramic coatings is the plasma electrolytic oxidation (PEO). However PEO can only be applied on self-passivating metals like aluminium, titanium, magnesium and their alloys. The present paper concerns a combination of cost-efficient arc spraying and flame spraying of Al coatings (Al99.5, AlCu4Mg1) on steel substrates and post-treatment by plasma-electrolytic oxidation (PEO). The microstructure and phase composition of generated oxide coatings are examined and discussed. The created Al2O3 layers show outstanding hardness up to 1600 HV0.1, good bonding strength and excellent abrasion resistance compared to atmospheric plasma-sprayed Al2O3-coatings. The results show the superior performance of PEO-coatings and demonstrate their applicability for technical components in extreme operating conditions.