Thermal analysis of functionally graded mullite - La2O3 coated aluminium alloy piston using plasma spraying

Aluminium alloy pistons used in I.C. engines are exposed to high temperature and may contribute to high thermal residual stresses on the piston crowns. The pistons operate ineffectively due to lack of appropriate coatings on pistons. The application of Thermal Barrier Coatings (TBC) on the components of IC engine reduces the combustion chamber heat rejection significantly. The current work is put to determine the temperature distribution of ceramic coated piston using finite element software and reduce the effect of thermal stress. Prior to coating on piston crowns, La2O3 is mixed at 10%, 20% and 30% proportions with Mullite and plasma spray deposited on A356 aluminium alloy substrate with base coat of NiCr for determination of best performing composition. The experimental test results from tensile test performed as per ISO - 1608 and adhesive test performed as per ASTM C633-79 confirms that 10% La2O3 mixed with mullite produces improved performance of 10% and 27% improved respectively. In addition, the temperature distribution study performed using Ansys 11 software for 10% La2O3 mixed with mullite also produced 12% less thermal stresses during combustion operation in comparison with uncoated pistons. Mullite - La2O3 TBC coatings support in maintaining the combustion temperature and supports in reduction of HC emission during operation. The reduction in thermal stresses of engine components significantly improving the performance and its service life.