Metallurgical evaluation was conducted on thermally-sprayed bronze coatings that are commonly found in gas turbine labyrinth seals. These bronze coatings serve as abradable surfaces for air/air and air/oil seals operating at low temperatures. As-coated and post-oxidation coating microstructures were examined metallographically to establish the coating’s functional life at various operating temperature ranges. Oxidation tests at several temperatures and times were carried out in order to construct a time-temperature map that could be used to predict the useful life of this bronze coating as correlated to gas turbine bronze seals returned from field service. Scanning electron microscopy in conjunction with polarized light microscopy were utilized to identify the presence of red cuprous oxide, a key factor in the determining the extent of internal oxidation.

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