Thermal analysis and failure behaviour of YSZ thermal barrier coatings on low heat rejection diesel engine piston

Abstract

To investigate the failure behaviour of thermal barrier coatings (TBCs) on diesel engine piston, YSZ TBCs were sprayed onto the 2A70 aluminium by atmospheric plasma spray. Finite element model was employed to estimate the temperature and stress distributions in TBCs on piston. Both the temperature and stress distributions were affected by the thickness of TBCs. The simulation results indicated that the bond coat/substrate interface was the weak region due to large interfacial stress. The thermal cycling performance of TBCs was evaluated by a burner rig test facility. The phase transformation of weak region during thermal cycling was analysed. After about 2000 cycles, the cracks along bond coat/substrate interface and the oxidation of the heat affected zone (HAZ) were visible. The TBCs spalled after about 4000 cycles, which is mainly attributed to the large thermal mismatch stress at bond coat/substrate interface and severe oxidation of HAZ.