Structure analysis and formation mechanism of Ce doped Al2O3 coatings prepared by cathode plasma electrolytic deposition

Abstract

In the present study, CPED technology was used to prepare Ce doped Al2O3 coatings with different doping contents on 316 stainless steel substrates. The effects of the Ce contents, deposition voltages and heat treatment process on the phases and structures of the coatings were analyzed, and the formation mechanism during the CPED process was studied. The results showed that the Ce was existed in the forms of two states: solid solution state and oxide state (CeO2). The presence of the CeO2 resulted in a fine crystalline structure of the Al2O3 and compression stress in the Al2O3 coatings due to the thermal mismatch. Stress release and phase transitions from γ-Al2O3 to η-Al2O3, and α-Al2O3 occurred during the heat treatment process, and the doping of Ce by CPED method can effectively inhibit the phase transition to α-Al2O3. It was demonstrated that the pore sizes and the porosity of the coatings were related with the dielectric constants of the coatings, and high content of Ce had a negative effect on the porous structure.