Controlled spraying resolves main problems in nanostructured thermal barrier coatings

Iranian researchers from the Department of Materials Engineering, Malek-Ashtar University of Technology designed and optimized various parameters of nanostructured coatings and succeeded in the production of a very high-quality coating to resolve the main problems in the spraying and adhesion of nanostructured thermal barrier coatings to the sub-layer. Thermal barrier coatings play an important role in protecting the pieces that operate at very high temperatures. When these coatings are used, the working temperature of the turbine may increase due to their very small thermal conductivity and the ability to stand thermal slopes. Therefore, higher thermodynamic efficiency and lower pollution are obtained. In this research, the optimization of spray condition was chosen as the main objective. The researchers produced a coating with very high quality by designing and optimizing various parameters of spraying. Sub-layers made of nickel-based superalloy (Inconel 738LC) were chosen in this research. The reason for the selection was simulation at industrial condition, to the extent that the alloy is used in the production of turbine blades. In this research, the values of adhesive strength were calculated 24.6 and 38.12 MPa for conventional yttria stabilized zirconia (YSZ) thermal barrier coatings and plasma-sprayed nanostructure, respectively. However, the bonding strength of plasma-sprayed ceramics on metallic sub-layers has been reported 15-25 MPa. Therefore, adhesive strength calculated for the two coatings have been very desirable, specially for the nanostructured coating. It shows the correct selection of parameters in plasma-spraying process. The plan has applications in power plants, petroleum and gas industries, automobile manufacturing, steam turbines, heat exchangers, boilers, gas turbines, and the coating of all pieces that operate at high temperatures. Results of the research have been published in Ceramics International, vol. 39, issue 8, December 2013, pp. 8805-8813.