Process for carbon bearing MCrAlY coating

Claim 1

A method of providing a coating having wear, corrosion, and oxidation resistance in a gas turbine environment, on a superalloy substrate, which comprises the steps of: (a) mixing MCrAlY powders with Cr 3 C 2 powders, wherein M is a metal selected from the group consisting of Ni, Co, Fe, or mixtures thereof, the powders having particle sizes less than 44 microns, with the Cr 3 C 2 having a first average particle size and being present in sufficient quantity in the mixture to produce the composition and structure after spraying which is indicated in step (b); (b) plasma spraying the powders so that they impinge on, adhere to the substrate, and interact during spraying to produce a coating which consists essentially of a MCrAlY matrix rich in carbon and containing fine carbides of the order of 1-2 microns size and coarse chromium carbides of the order of 12 microns size, the average size of the Cr 3 C 2 carbides being smaller than the said first average particle size, and the coating having at least 0.6 weight percent carbon.

Claim 2

A method of providing a coating having wear, corrosion, and oxidation resistance in a gas turbine environment, on a superalloy substrate, which comprises the steps of: (a) mixing MCrAlY powders with Cr 3 C 2 powders, wherein M is a metal selected from the group consisting of Ni, Co, Fe, or mixtures thereof, the powders having particle sizes less than 44 microns, with the Cr 3 C 2 having a first average particle size and being present in sufficient quantity in the mixture to produce the composition and structure after spraying which is indicated in step (b); (b) plasma spraying the powders so that they impinge on, adhere to the substrate, and interact during spraying to produce a coating which consists essentially of a MCrAlY matrix rich in carbon and containing fine carbides of the order of 1-2 microns size and coarse chromium carbides of the order of 12 microns size, the average size of the Cr 3 C 2 carbides being smaller than the said first average particle size, and the coating having at least 0.6 weight percent carbon.

Claim 5

The method of claims 1 or 2 wherein at least a portion of the mixture of MCrAlY powders with Cr 3 C 2 is replaced by a master alloy particulate consisting of MCrAlY and C and having a particle size less than 44 microns, any Cr 3 C 2 present within the master alloy particulate having an average particle size of about 15 microns.