Shin, D: Development of Metal Based Thermal Barrier Coatings

Metal-based thermal barrier coatings (MBTBCs) have been produced, using Induction plasma spraying (IPS) of nanostructured alloy powders. Important advances have been made over recent years to ceramic-based thermal barrier coatings (TBCs) for internal combustion engines application, but they are not yet applied in mass production situations. Besides the important economic considerations, the reliability of ceramic TBCs is also an issue, due to the difficulty of predicting in-service lifetime. Through engineering of the nano/amorphous structure of MBTBCs, their thermal conductivity can be made as low as those of ceramic-based TBCs. The thermal conductivity of MBTBCs was found to be as low as 1.99W/m/K. Thermal expansion coefficient (TEC) of MBTBCs was 13E-6/K, which is close to the TEC of cast iron and thus, closer to the TEC values of aluminium alloys than are conventional TBCs. Fracture toughness of MBTBCs has also been assessed by use of Vickers hardness tests, with a 500g load for 15s, and there are no measurable crack developments around indented areas on MBTBCs tested.