## 1 Introduction  
One of the main ongoing research topics for increasing combustion efficiency in engines is to lower the heat transfer from the combustion chamber to the outside and to increase the mean effective pressure by coating some part of the combustion chamber surfaces of the engine with ceramic-based materials. In a diesel engine, approximately 30% of the fuel energy is lost energy due to the heat losses in the combustion chamber. In order to reduce this amount of energy loses; studies in diesel engines are focused on thermal barrier coating. In recent years, studies have been carried out on thermal barrier coating of the piston surface, valves, piston crown and cylinder head in diesel engines. In thermal barrier coating (TBC) applications, the aim is to reduce the heat flow through the piston walls with the help of materials with low thermal conductivity. Application of TBC to the combustion chamber elements affects combustion efficiency, engine performance and exhaust emissions [1]. Yttria-stabilized zirconia (YSZ) is widely used in thermal barrier coating applications in diesel engines. In order to improve the adhesion of the coating, a primer layer with a low coefficient of thermal expansion is applied between the piston surface and the TBCsurface. The coating thickness ranges from 0.1 mm to 0.5 mm [2]. The ceramic coating process is carried out by various methods, but the most widely used is the plasma spray coating method [3]. The difficulty of application lies in the different operating conditions in diesel engines. Diesel engines have a high operating temperature, with engine speeds of around 1500-3000 rpm under normal conditions. For this reason, coatings are exposed to heat and pressure at a very high rate and frequency [4]. Therefore, the coating application must withstand these high-frequency heat and high-pressure operating conditions. It is important that both the coating materials and coating application be chosen well in accordance with these difficult working conditions. In diesel engines, it is necessary to analyze the working conditions in the combustion chamber and the pressure and thermal effects on the surfaces. In this study, the effects of different partitioned thermal barrier coating applications on combustion and thermal and pressure stress were investigated for a diesel engine. The first research on diesel engines with thermal barrier coatings was conducted by [PERSON] in the mid-1970s [5]. Many researchers have investigated the effect of thermal barrier coating (TBC) on heat losses and fuel efficiency in diesel engines. As a result of the studies, most researchers found a decrease in fuel consumption and an improvement in engine performance [6; 7]. When coating piston surfaces, the first layer is the substrate, which is mostly steel, cast iron or aluminum. The primer, known as the intermediate coat, has two important functions. First, it should protect the substrate from oxidation, and second, it should provide mechanical bonding with the top coating layer on the piston surface. When the higher operating temperature is reached, oxygen penetrates into the surface between the bond layer and the TBC through micro cracks and forms a thick oxide layer in that area [8]. The upper layer consisting of ceramic material is a layer with low thermal conductivity that provides thermal insulation. [PERSON] et al. [9] applied TBC on the engine cylinder head and valves with zirconia stabilized with Yttria. They used a coating thickness of 300-350 microns and a NiCarAl undercoating layer thickness of 30 microns. They found an increase of 7-20% in exhaust gas temperatures in ceramic coated engines. It has been stated that this heat energy increase will be restored to the system with a turbocharging system combination, leading to an increase in engine performance. The aim is to reduce heat losses and increase engine performance by coating the pistons.