Diesel engines are used in many industrial applications in addition to those in cars. Developing diesel engines to be more efficient with less fuel consumption, low gas emissions, and high performance an objective of many researchers. Ceramic thermal barrier coatings (TBC) have been identified as the most promising method of developing diesel engines.
In this study, a new coating (TBC) as a single layer, attempting to replace a yttria stabilize zirconia coating that contains three layers to overcome many issues such as spallation. Beside owing lower thermal conductivity of new coating ,It improves combustion features, resulting in enhanced efficiency and economic and environmental performance of the diesel engine. The A304 alloy steel diesel piston was brought from oil products distribution company stores (OPDC) / Babylon branch. Eight coatings blends were prepared to investigate their properties using ceramic powder materials, that is, magnesium oxide (MgO), Aluminum oxide (Al2O3), Silicon oxide (SiO2), and zirconium oxide (ZrO2), at different percentages and were numbered (M1,M2,…M8). Two of these blends show the lowest thermal conductivity among others, namely, M4 which contain (MgO=30%,Al2O3=45%,SiO2=25%),and M7 which contain (MgO=35%,Al2O3=30%,SiO2=25%,ZrO2=10%).
Flame spraying was the technique adopted using an acetylene and oxygen mixture under a pressure of 0.6 bar and 5 bar for acetylene and oxygen, respectively. Furthermore, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Atomic force microscopy (AFM) tests were carried out to identify and characterize the microstructure and morphology of the powders and coated layer. Thermal conductivity, coating layer thickness, porosity content , and adhesion strength are also tested to determine the thermal conductivity of the TBC coating layer, which confirmed the thermal conductivity of M4 and M7 was the lower among other blends , which have the lowest values of 0.831334 W/m .c and 0.72186 W/m .c, respectively. The coating layer thickness was about 0.6 mm with a porosity content of about 15–20%.The highest adhesion strength of specimens was about 20 MPa, which was for the M7 blend.
The results are used in the simulation process using Ansys workbench 16.1 simulation software as a steady-state thermal condition. The model was built using the actual dimensions of the diesel piston and coating layer, and it was then simulated with an initial and boundary condition (700C as the operation temperature and 30C as the initial and environmental temperature).The model geometry was discretized and optimized until obtaining the best number of elements, which is (213514) elements and (303548) nodes with the quadratic shape. The obtained results confirmed the temperature was lowered at the piston crown surface after coating to (534 Co and 513 Co) for M4 and M7 specimens coated, respectively. That means the lower temperatures ranged between 165 Co and 190Co.