Thermal Barrier Coatings (TBCs) Are Advanced Materials Systems Applied To Metallic Surfaces That Operate At Elevated Temperatures

Thermal Barrier Coatings

As a method of exhaust heat management, Thermal Barrier Coatings (TBCs) are sophisticated materials systems that are typically applied to metallic surfaces working at high temperatures, such as gas turbine or aero-engine components. These thermally insulating coatings, which range in thickness from 100 micrometres to two millimetres, protect components from intense heat loads and can withstand a significant temperature differential between the load-bearing metals and the coating surface.

By minimising the heat exposure of structural components, these coatings can increase operating temperatures while increasing part life by lowering oxidation and thermal fatigue. In some turbine applications, Thermal Barrier Coatings allow working fluid temperatures greater than the melting point of the metal air foil in combination with active film cooling. There is a strong incentive to create new and enhanced TBCs since there is a growing need for more efficient engines that operate at higher temperatures with better durability/lifetime and thinner coatings to minimise parasitic mass for rotating/moving components.

Thermal Barrier Coatings material requirements are comparable to those for heat shields, however emissivity is sometimes more critical in the latter use. In order to function successfully in challenging thermo-mechanical settings, a Thermal Barrier Coatings must adhere to a set of standards. Adequate porosity and proper matching of thermal expansion coefficients with the metal surface that the TBC is covering are required to handle thermal expansion loads during heating and cooling. To avoid substantial volume fluctuations, which happen during phase transitions and might cause the coating to fracture or spall, phase stability is necessary.

Oxidation resistance and respectable mechanical qualities for spinning, moving, or in contact components are required in air-breathing engines. A high melting point, no phase transition between room temperature and operating temperature, low thermal conductivity, chemical inertness, similar thermal expansion match with the metallic substrate, good adherence to the substrate, and a low sintering rate for a porous microstructure are thus the general requirements for an effective Thermal Barrier Coatings. The amount of materials that may be employed is highly constrained by these requirements, with ceramic materials often being able to provide the necessary qualities.