Microstructure, temperature estimation and thermal shock resistance of PEO ceramic coatings on aluminum

Plasma electrolytic oxidation (PEO) is a novel surface technique for producing ceramic coatings on valve metals and their alloys. In this paper, microstructure, temperature estimation and thermal shock resistance of the ceramic coatings formed on pure aluminum by hetero-polar pulsed current ceramic synthesizing system were investigated. Results show that the coating roughness becomes greater and the plasma discharge channel populations in the ceramic coatings decrease while the pores enlarge with PEO treatment time. in addition, the surface morphology of the ceramic coating indicates that melting and solidifying process happen alternately in the process. The results also show that the coatings have a good thermal shock resistance. Moreover, the temperature and the temperature rise rate of the plasma discharge channels were investigated, and a formula for calculating the temperature and the temperature rise rate of the plasma discharge channels at any time during the PEO process was deduced. (C) 2007 Elsevier B.V. All rights reserved.