| abstract |
This invention relates to blades for a gas turbine engine, said blades having an inner end adapted for mounting on a hub and a blade tip located opposite the inner end, and wherein at least a portion of the blade tip is coated with a thermally sprayed coating of a high purity yttria or ytterbia stabilized zirconia powder, said thermally sprayed coating having a density greater than 88% 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 blade tip 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 blade tip and in a plane perpendicular to the blade tip, and 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). This invention also relates to a process for producing a coating on at least a portion of a tip of a blade for a gas turbine engine. |