Thermal barrier coatings (TBCs) have been developed for application to aircraft engine components to improve service life in an increasingly hostile thermal environment. The choice of TBC type is related to the component, intended use, and economics. Selection of electron beam physical vapor deposition processing for turbine blade is due in part to part size, surface finish requirements, thickness control needs, and hole closure issues. Process development ofPVD TBCs has been carried out at several different sites, including GE Aircraft Engines (GEAE). The influence of processing variables on microstructure is discussed, along with the GEAE development coater and initial experiences of pilot line operation.
X-ray photoelectron spectroscopy (XPS) analysis of sputterdeposited calcium phosphate coatings on titanium substrates revealed four distinct zones. The ambient-exposed surface exhibited elevated concentrations of carbon because of atmospheric contamination. The bulk zone contained relatively constant concentrations of calcium, oxygen, phosphorus, and fluorine indicating the chemistry for calcium fluoride (CaF2) and fluorapatite (Ca,(PO4),F) formation. The transitional zone exhibited elevated titanium and oxygen photoelectron peaks suggesting the coexistence of calcium phosphate compounds within the titanium oxide. The substrate was shown to be identical to the passhated titanium surface prior to deposition. [Key words: hydroxyapatite, flouroapatite, calcium phosphate, coatings, X-ray photoelectron spectroscopy.]
The processing variables which lead to the rough, convoluted surface topologies of platinum modified aluminide coatings were studied. Platinum deposition techniques such as electroplating, ion plating, and sputtering were examined as were postplating diffusion treatments and aluminizing processes. It was found that while the initial Pt surface could be varied by the deposition process and procedures selected, the principal factor influencing surface topology was Pt substrate (IN-738) interdiffusion. Subsequent aluminizing processing had a much smaller additional effect. The effects of the surface roughness and phases and porosity found in the Pt layer on subsequently aluminized coatings performance are not known.
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