Low cost aluminide process for moderate temperature applications

A gas turbine nozzle coated with a diffusion barrier coating the coating formed by the method comprising:

• providing a metal substrate;
• cleaning the substrate of foreign material;
• coating the metal substrate with a layer of aluminum containing paint, said paint comprising substantially aluminum, solvents, and binders;
• drying the substrate;
• baking the layer of aluminum containing paint to a first temperature for a first period of time sufficient to volatilize solvents remaining in the layer of aluminum-based paint;
• baking the layer of aluminum containing paint to a second temperature for a second preselected period of time sufficient to remove the binders in the layer of aluminum containing paint in an inert atmosphere, the remaining layer comprising substantially aluminum of sufficient thickness;
• heating the metal substrate having a substantially continuous layer of aluminum to a third temperature for a third period of time sufficient to diffuse the aluminum into the substrate to form a diffusion aluminide layer;
• heating the diffusion aluminide layer to a fourth temperature for a fourth period of time to form a continuous, adherent alumina scale over the diffusion aluminide coating;
• and
• cooling the substrate.

A gas turbine nozzle coated with a diffusion barrier coating, the coating formed by the method comprising:

• providing a metal substrate;
• cleaning the substrate of foreign material;
• coating the metal substrate with a layer of aluminum containing paint, said paint comprising substantially aluminum, solvents, and binders;
• drying the substrate;
• baking the layer of aluminum containing paint to a first temperature for a first period of time sufficient to volatilize solvents remaining in the layer of aluminum-based paint;
• baking the layer of aluminum containing paint to a second temperature for a second preselected period of time sufficient to remove the binders in the layer of aluminum containing paint in an inert atmosphere, the remaining layer comprising substantially aluminum of sufficient thickness;
• heating the metal substrate having a substantially continuous layer of aluminum to a third temperature for a third period of time sufficient to diffuse the aluminum into the substrate to form a diffusion aluminide layer;
• heating the diffusion aluminide layer to a fourth temperature for a fourth period of time to form a continuous, adherent alumina scale over the diffusion aluminide coating;
• cooling the substrate;
• and
• applying an outer coating over the diffusion metal layer after cooling the substrate, the alumina scale forming a diffusion barrier between the applied outer layer and the substrate underlying the alumina scale.

A gas turbine nozzle coated with a diffusion barrier coating, the coating formed by the method comprising:

• providing a metal substrate;
• cleaning the substrate of foreign material;
• coating the metal substrate with a layer of aluminum containing paint, said paint comprising substantially aluminum, solvents, and binders;
• drying the substrate;
• baking the layer of aluminum containing paint to a temperature in the range of about 300° F. to about 485° F. for a time in the range of about one hour to about three hours to volatilize solvents remaining in the layer of aluminum-based paint;
• baking the layer of aluminum containing paint to a temperature in the range of about 750° F. to about 930° F. for a period of time in the range of about one hour to about three hours to remove the binders in the layer of aluminum containing paint in an inert atmosphere, the remaining layer comprising substantially aluminum of sufficient thickness;
• heating the metal substrate having a substantially continuous layer of aluminum to a temperature in the range of about 1100° F. to about 2000° F. for a period of time in the range of about one hour to about fifty hours to diffuse the aluminum into the substrate to form a diffusion aluminide layer;
• heating the diffusion aluminide layer to a temperature in the range of about 1200° F. to about 1800° F. for a period of time in the range of about two hours to about four hours to form a continuous, adherent alumina scale over the diffusion aluminide coating;
• and
• cooling the substrate.

A gas turbine nozzle coating with a diffusion barrier coating, the coating formed by the method comprising:

• A gas turbine nozzle coated with a diffusion barrier coating, the coating formed by the method comprising:
• providing a metal substrate;
• cleaning the substrate of foreign material;
• coating the metal substrate with a layer of aluminum containing paint, said paint comprising substantially aluminum, solvents, and binders;
• drying the substrate;
• baking the layer of aluminum containing paint to a temperature in the range of about 300° F. to about 485° F. for a time in the range of about one hour to about three hours to volatilize solvents remaining in the layer of aluminum-based paint;
• baking the layer of aluminum containing paint to a temperature in the range of about 750° F. to about 930° F. for a period of time in the range of about one hour to about three hours to remove the binders in the layer of aluminum containing paint in an inert atmosphere, the remaining layer comprising substantially aluminum of sufficient thickness;
• heating the metal substrate having a substantially continuous layer of aluminum to a temperature in the range of about 1100° F. to about 2000° F. for a period of time in the range of about one hour to about fifty hours to diffuse the aluminum into the substrate to form a diffusion aluminide layer;
• heating the diffusion aluminide layer to a temperature in the range of about 1200° F. to about 1800° F. for a period of time in the range of about two hours to about four hours to form a continuous, adherent alumina scale over the diffusion aluminide coating;
• cooling the substrate;
• and
• applying an outer coating over the diffusion metal layer after cooling the substrate, the alumina scale forming a diffusion barrier between the applied outer layer and the substrate underlying the alumina scale.

A gas turbine nozzle coating with a diffusion barrier coating, the coating formed by the method comprising:

• providing a metal substrate;
• cleaning the substrate of foreign material;
• coating the metal substrate with a layer of aluminum containing paint, said paint comprising substantially aluminum particles about 0.5 microns in thickness, solvents, and binders;
• drying the substrate;
• baking the layer of aluminum containing paint to a temperature in the range of about 300° F. to about 485° F. for a time in the range of about one hour to about three hours to volatilize solvents remaining in the layer of aluminum-based paint;
• baking the layer of aluminum containing paint to a temperature in the range of about 750° F. to about 930° F. for a period of time in the range of about one hour to about three hours to remove the binders in the layer of aluminum containing paint in an inert atmosphere, the remaining layer comprising substantially aluminum of sufficient thickness;
• heating the metal substrate having a substantially continuous layer of aluminum to a temperature in the range of about 1100° F. to about 2000° F. for a period of time in the range of about one hour to about fifty hours to diffuse the aluminum into the substrate to form a diffusion aluminide layer;
• heating the diffusion aluminide layer to a temperature in the range of about 1200° F. to about 1800° F. for a period of time in the range of about two hours to about four hours to form a continuous, adherent alumina scale over the diffusion aluminide coating;
• and
• cooling the substrate.