High purity zirconia-based thermally sprayed coatings and processes for the preparation thereof

摘要

This invention relates to thermally sprayed coatings of a high purity yttria or ytterbia stabilized zirconia powder, said high purity yttria or ytterbia stabilized zirconia powder comprising from about 0 to about 0.15 weight percent impurity oxides, from about 0 to about 2 weight percent hafnium oxide (hafnia), from about 6 to about 25 weight percent yttrium oxide (yttria) or from about 10 to about 36 weight percent ytterbium oxide (ytterbia), and the balance zirconium oxide (zirconia). Thermal barrier coatings for protecting a component such as blades, vanes and seal surfaces of gas turbine engines, made from the high purity yttria or ytterbia stabilized zirconia powders, have a density greater than 88% of the theoretical density with a plurality of vertical macrocracks homogeneously dispersed throughout the coating to improve its thermal fatigue resistance.

主权项

1. A thermally sprayed coating of a high purity yttria or ytterbia stabilized zirconia powder deposited on a substrate, said high purity yttria or ytterbia stabilized zirconia powder comprising less than or equal to about 0.15 weight percent impurity oxides, less than or equal to 2 weight percent hafnium oxide (hafnia), from about 6 to about 25 weight percent yttrium oxide (yttria) or from about 10 to about 36 weight percent ytterbium oxide (ytterbia), and the balance zirconium oxide (zirconia); said impurity oxides comprising less than or equal to about 0.02 weight percent silicon dioxide (silica), less than or equal to about 0.005 weight percent aluminum oxide (alumina), less than or equal to about 0.01 weight percent calcium oxide, less than or equal to about 0.01 weight percent ferric oxide, less than or equal to about 0.005 weight percent magnesium oxide, and less than or equal to about 0.01 weight percent titanium dioxide; said high purity yttria or ytterbia stabilized zirconia powder having a particle size of from about 1 to about 150 microns; wherein said thermally sprayed coating has a density greater than 90% of the theoretical density with a plurality of vertical macrocracks substantially homogeneously dispersed throughout the coating in which a cross-sectional area of the coating normal to the substrate exposes a plurality of vertical macrocracks extending at least half the coating thickness in length up to the full thickness of the coating and having from about 5 to about 200 vertical macrocracks per linear inch measured in a line parallel to the surface of the substrate and in a plane perpendicular to the surface of the substrate; wherein said substrate comprises a blade, vane or seal surface of a gas turbine engine.