Chromalloy Gas Turbine Corporation

Thermal barrier coatings (TBC) based on zirconia are being used to insulate critical hot-section components of gas turbine engines either to reduce cooling air requirements or to increase the gas temperature, thereby increasing the thermodynamic efficiency of the engine. Development of TBC's by electron beam physical vapor deposition results in a columnar ceramic structure caused by the 1ine-of-sight deposition process. This allows the coating to withstand very high thermal shocks due to the alleviation of the residual stresses resulting between the bond coating and the TBC from the differential thermal expansion coefficients. Factors involved in the deposition by PVD and their effects on adhesion and durability of the TBC'S, bond coating composition's key role in the adhesion process and optimum compositions, and Mach 0.3 barrier rig testing and engine testing of TBC components are important, as well as further directions in the PVD ceramic coating program both in terms of compositions and process parameters.

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