Study on thermal-mechanical coupling of the ceramic layer in diesel engine piston with thermal barrier coating

Abstract

Piston performance has an important on vehicle reliability, efficiency and exhaust emissions. The thermal barrier coating is an effective method to prevent heat transfer from combustion chamber to the substrate. The numerical model of thermal barrier coating piston is established by using finite element method, and a comprehensive thermal-mechanical result is given to determine the influence of ceramic thickness on ceramic layer and substrate. Compared with uncoated piston, the maximum temperature and the thermal stress of substrate decreased by 3.34%, 4.09%, 5.19%, 5.95% and 6.69%, corresponding to ceramic thicknesses of 0.15mm, 0.2 mm, 0.25 mm ,0.3 mm and 0.35mm. The maximum thermal stress decreases from 78 MPa to 73 MPa. For ceramic layer of the thermal barrier coating piston, the maximum temperature appears at the top surface of the ceramic layer, while the maximum thermal stress occurs at the bottom of the ceramic layer. As the ceramics thickness increased from 0.15mm to 0.35mm, the maximum temperature of the ceramic layer increased from 322? to 377?, while the maximum thermal stress decreased from 95 MPa to 89 MPa. Thermal-mechanical coupled stress analysis shows that the maximum coupling stress occurs at the pinhole and its value does not change significantly. The thickness of the ceramic layer has little effect on the pinhole, but has a great influence on the ceramic layer.