Methods of applying chromium diffusion coatings onto selective regions of a component

A method for producing a localized platinum-group-metal (PGM) modified chromium diffusion coating onto a first region of a substrate and a localized PGM-modified aluminide diffusion coating onto a second region of a substrate, comprising the steps of:

• depositing a first platinum-group-metal (PGM) layer onto the first region of the substrate, said PGM layer consisting of at least one element selected from the group consisting of platinum, iridium, rhodium, palladium, and any combination thereof;
• providing a chromium-containing slurry;
• applying the chromium-containing slurry onto the first region of said PGM layer of the substrate, wherein said step of applying the chromium-containing slurry is characterized by an absence of diffusion stop-off masking;
• providing an aluminum-containing material;
• heating the chromium-containing slurry and the aluminum-containing material in a protective atmosphere to a predetermined temperature for a predetermined duration;
• diffusing chromium into the first region;
• diffusing aluminum into the second region in the absence of diffusion stop-off masking;
• forming the localized PGM modified chromium diffusion coating along the first region, said PGM modified chromium diffusion coating having a surface enrichment of both chromium and PGM and further wherein said coating has a microstructure characterized by a substantial reduction in nitride and oxide inclusions and reduced levels of α-Cr phase in comparison to conventional chromizing processes;
• and
• forming the localized PGM modified aluminide-diffusion coating along the second region.

A method for producing a localized PGM modified chromium diffusion coating, and a localized PGM-modified aluminide diffusion coating onto selected regions of a blade simultaneously, said method comprising the steps of:

• depositing a first platinum-group-metal (PGM) layer onto a shank of the blade, said PGM layer consisting of at least one element selected from the group consisting of platinum, iridium, rhodium, palladium, and any combination thereof;
• providing a chromium-containing slurry;
• applying the chromium-containing slurry onto an external region of the shank of the blade, to create a partially coated blade;
• providing aluminum-containing material within the retort;
• loading the partially coated blade into the retort;
• heating the partially coated blade;
• generating aluminum containing vapors and chromium containing vapors;
• diffusing chromium from the chromium-containing vapors into the external region of the shank of the blade;
• diffusing aluminum from the aluminum-containing vapors into an airfoil of the blade;
• forming the localized and PGM-modified chromium diffusion coating along the shank, said chromium diffusion coating having a surface enrichment of both chromium and PGM and further wherein said coating has a microstructure characterized by a substantial reduction in nitride and oxide inclusions and reduced levels of α-Cr phase in comparison to conventional chromizing processes;
• and
• forming the localized PGM-modified aluminide-diffusion coating along the airfoil.

A method for producing a platinum-group-metal (PGM) modified chromium diffusion coating onto selected regions of a substrate, comprising the steps of:

• providing a chromium-containing slurry;
• applying the chromium-containing slurry onto localized surfaces of the substrate;
• curing the slurry;
• heating the cured slurry in a protective atmosphere to a predetermined temperature for a predetermined duration;
• generating chromium-containing vapors;
• diffusing the chromium from said chromium-containing vapors into said localized surfaces to form the chromium diffusion coating, said coating having a microstructure characterized by a substantial reduction in nitride and oxide inclusions and reduced levels of α-Cr phase in comparison to conventional chromizing processes;
• depositing a PGM layer onto said chromium diffusion coating, said PGM layer consisting of at least one element selected from the group consisting of platinum, iridium, rhodium, palladium, and any combination thereof;
• performing diffusion treatment in a protective atmosphere to a predetermined temperature for a predetermined duration, and diffusing the PGM into said chromium diffusion coating;
• and
• producing said PGM-modified chromium diffusion coating onto the selected regions of the substrate, wherein said selected regions correspond to the localized surfaces.