Patent ID: 9267218
Filing Date: 2016-02-23
CPC Classification: C22C,C25D,F01D,F05D

Claim Text:
1. A method of forming a bucket for use in the last stage of a steam turbine engine, said method comprising: forming a bucket comprising a titanium-based alloy having between about 3% and 6.25% by weight aluminum, up to 3.5% vanadium, up to 2.25% tin, up to 2.25% zirconium, between about 1.75% and 5.0% molybdenum, up to 2.25% chromium, up to 0.7% silicon and up to 2.3% iron, with the balance being titanium; applying a high voltage to a leading edge of said bucket to form a transition layer of titania having a plurality of pores and wherein the transition layer of titania has a thickness of from about 20 microns to about 150 microns, said titania directly adhered to the titanium-based alloy, wherein an electrical field at the leading edge is controlled by an insulator positioned in an electrolyte, and sealing the transition layer of titania by filling the plurality of pores with a material selected from the group consisting of chromium, cobalt, nickel, polyimide, polytetrafluoroethylene and polyester.