Microstructure and Thermal-protective Property of CPED Coating with ZrO₂ Nanoparticles Addition on Al-12Si Alloy

Abstract

A novel thermal-protective coating has been successfully prepared by CPED process on a cast Al-12%Si alloy with the addition of ZrO₂ nano-particles in the electrolyte. The microstructures and phase composition of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. With ZrO₂ nanoparticles addition, the cathode plasma discharge on the coating surface is more obvious than that without ZrO₂ nanoparticles addition, the coating is more uniform and compact, and the thickness of the coating increases. Furthermore, the content of Zr and Y elements increases and the degree of crystallization of the coating is more complete. The formation of the solid solution of yttrium stabilized zirconia is promoted by cathode plasma discharge. In addition, the thermal insulation temperature increases as ZrO₂ nano-particles are added to the electrolyte. After 1 000 cycles of thermal shock, there was no cracking in the coating surface layer, which indicated that the CPED coating with ZrO₂ nanoparticles addition possessed a good thermal shock resistance.

Keywords

Al-12Si piston alloy / cathode plasma electrolytic deposition (CPED) / ZrO₂ nano-particles / heat-shielding performance / thermal shock performance