Alloy-coated gas turbine blade and manufacturing method thereof

A gas turbine blade having a coated layer provided on the surface of a base material made of a heat resistant alloy and exhibiting an opulent high-temperature anticorrosive property and oxidation resistant property,

• said coated layer comprising two layers, one layer being a Co--Ni based lower alloy-coated layer containing Cr, Al and Y, and provided as a portion which contacts said base material, and the other layer being a Ni based upper alloy-coated layer containing Cr, Al and Y, and provided on the lower alloy-coated layer, wherein said lower alloy-coated layer consists of 10-30 wt % Cr, 5-15 wt % Al, 0.1-1.5 wt % Y, remaining Co--Ni, the Co/Ni ratio of which is at least 0.5 and inevitable impurities, and said upper alloy-coated layer consists of 10-30 wt % Cr, 5-25 wt % Al, 0.1-1.5 wt % Y, remaining Ni and the inevitable impurities, wherein the Al content of said upper alloy-coated layer is, in part, diffused into the upper layer to exhibit a maximum Al concentration at the outermost surface of said upper layer and the Al concentration is continuously reduced at most up to the innermost surface of said upper layer, wherein the maximum concentration of Al in the upper alloy-coated layer is 15-25 wt % and minimum concentration of Al in the upper layer is 5-15 wt % and is less than the maximum concentration.

A method of manufacturing an alloy-coated gas turbine blade having a coated layer provided on the surface of a base material made of a heat resistant alloy and exhibiting an opulent high-temperature anticorrosive property and oxidation resistant property, said method comprising the steps of:

• forming, on the base material surface, a lower alloy-coated layer a principal element of which is any one of Co and Co--Ni alloy, said lower alloy-coated layer containing Cr, Al and Y, wherein said lower alloy-coated layer consists of 10-30 wt % Cr, 5-15 wt % Al, 0.1-1.5 wt % Y, remaining Co or Co--Ni alloy in which the Co/Ni ratio is at least 0.5 and inevitable impurities,
• forming a Ni based upper alloy-coated layer containing Cr, Al and Y on the surface of said lower alloy-coated layer, wherein said upper alloy-coated layer consists of 10-30 wt % Cr, 5-15 wt % Al, 0.1-1.5 wt % Y, remaining Ni and the inevitable impurities;
• permeating Al diffusively into said upper alloy-coated layer, wherein a maximum concentration of Al in the Al diffused upper alloy-coated layer is 15-25 wt %.