Method of applying continuously graded metallic-ceramic layer on metallic substrates

Claim 1

A method for applying a graded ceramic-metallic layer to a metallic substrate including the steps of: a. preheating the substrate to an elevated temperature; b. applying a metallic bond coat; c. reducing the substrate temperature; d. applying a graded metallic-ceramic layer, by depositing a multiplicity of thin layers of material, said layers having a largely metallic composition at the bond coat interface and a composition which increases in ceramic content and decreases in metallic content through the thickness of the graded layer, increasing the substrate temperature in approximate proportion to the ceramic content with the substrate temperature exceeding that achieved in step a. when the graded layer composition is essentially all ceramic said substrate temperature increasing being uninterrupted by periods of decreasing temperature prior to termination of the process whereby the resultant prestressed graded layer is capable of resisting severe thermal conditions without failure.

Claim 2

A method for applying a graded ceramic-metallic layer to a metallic substrate including the steps of: a. preheating the substrate to an elevated temperature; b. applying a metallic bond coat; c. reducing the substrate temperature; d. applying a graded metallic-ceramic layer, by depositing a multiplicity of thin layers of material, said layers having a largely metallic composition at the bond coat interface and a composition which increases in ceramic content and decreases in metallic content through the thickness of the graded layer, increasing the substrate temperature in approximate proportion to the ceramic content with the substrate temperature exceeding that achieved in step a. when the graded layer composition is essentially all ceramic said substrate temperature increasing being uninterrupted by periods of decreasing temperature prior to termination of the process whereby the resultant prestressed graded layer is capable of resisting severe thermal conditions without failure.

Claim 12

A method for producing a gas turbine engine air seal having a metallic substrate including the steps of: a. preheating the substrate to an elevated temperature; b. applying a metallic bond coat; c. reducing the substrate temperature; d. applying a graded metallic-ceramic layer by codepositing a mixture of metal and ceramic particulate material, starting with a predominately metallic mix at the bond coat interface and finishing with a substantially ceramic composition, by measuring the mass flow rates of the respective powders during the process and adjusting the mass flow rate according to a predetermined schedule, while increasing the substrate temperature in approximate proportion to the ceramic content in the mixture being sprayed with the substrate temperatures at conclusion of the graded layer deposition substantially exceeding the substrate temperature at which the bond coat was applied said substrate temperature increasing being uninterrupted by periods of decreasing temperature prior to termination of the process; e. applying a layer of pure ceramic over the graded layer by plasma spraying, providing intentional porosity in the outer portion of the ceramic layer by co-spraying the ceramic material with a fugitive material, and gradually reducing the substrate temperature while depositing the pure ceramic layer; and f. varying the distance between the plasma gun and the substrate during the process so as to produce a more dense coating near the substrate and a less dense coating away from the substrate.

Claim 13

A method for producing a gas turbine engine air seal having a metallic substrate including the steps of: a. preheating the substrate to an elevated temperature; b. applying a metallic bond coat; c. reducing the substrate temperature; d. applying a graded metallic-ceramic layer by codepositing a mixture of metal and ceramic particulate material, starting with a predominately metallic mix at the bond coat interface and finishing with a substantially ceramic composition, by measuring the mass flow rates of the respective powders during the process and adjusting the mass flow rate according to a predetermined schedule, while increasing the substrate temperature in approximate proportion to the ceramic content in the mixture being sprayed with the substrate temperatures at conclusion of the graded layer deposition substantially exceeding the substrate temperature at which the bond coat was applied said substrate temperature increasing being uninterrupted by periods of decreasing temperature prior to termination of the process; e. applying a layer of pure ceramic over the graded layer by plasma spraying, providing intentional porosity in the outer portion of the ceramic layer by co-spraying the ceramic material with a fugitive material, and gradually reducing the substrate temperature while depositing the pure ceramic layer; and f. varying the distance between the plasma gun and the substrate during the process so as to produce a more dense coating near the substrate and a less dense coating away from the substrate.