Temperature and thermal stress analyses of a ceramic-coated aluminum alloy piston used in a diesel engine

• Both temperature and thermal stress distribution vary with coating thickness.
• Temperature at the coated surface is significantly higher than that of the uncoated piston.
• High temperature appears at the crown center and the edges of the bowl rim.
• The maximum normal stress causing spalling of the ceramic occurs on the bond coat surface.
• The maximum normal stress on the substrate is nearly half that of the bond coat.

The goal of this paper is to determine both temperature and thermal stress distributions in a plasma-sprayed magnesia-stabilized zirconia coating on an aluminum piston crown to improve the performance of a diesel engine. Effects of the coating thickness on temperature and thermal stress distributions are investigated, including comparisons with results from an uncoated piston by means of the finite element method. Temperature and thermal stress analyses are performed for various coating thicknesses from 0.2 to 1.6 mm excluding the bond coat layer. Temperature at the coated surface is significantly higher than that of the uncoated piston. It is observed that the coating surface temperature increases with coating thickness by decreasing rate. Increase in the maximum temperature according to the uncoated piston is 64.3% for 1.0 mm thick coating. The higher combustion chamber temperature provided by means of coating results in the better thermal efficiency of the engine. It also provides for a reduction in the substrate surface temperature. The normal stress on the coated surface decreases with increasing coating thickness. Maximum normal stress occurs on the bond coat surface. Its value is approximately two and three times greater than substrate and coating surfaces respectively. Maximum shear stress occurs on the bond coat surface and its magnitude is nearly double that of the substrate surface.