Method for the production of an aluminum diffusion coating for oxidation protection

Abstract

For the production of an aluminum diffusion coating for oxidation protection of metallic components, components are masked in areas not to be coated, and unmasked areas are electrically-plated with aluminum in an aprotic solution at low temperature. Upon removal of the masking material, the components are heat-treated according to a certain high-temperature-time graph such that aluminum elements diffuse into the component alloy and alloy elements of the component diffuse into the aluminum coating. The method involves low manufacturing and material costs and guarantees a defined formation of the aluminum diffusion coating on the component portions to be protected.

1 . A method for the production of an aluminum diffusion coating for oxidation protection of a metallic component, comprising:
 masking certain portions of the component;   applying aluminum to unmasked surfaces of the masked component by electro-plating in a water and oxygen free organic electrolyte;   subsequently removing the masking; and   then heat treating the unmasked component in at least one of a protective gas atmosphere and a vacuum according to a given high-temperature-time graph, such that in a surface-near zone of the component, the aluminum diffuses into the component and alloy elements of the component diffuse in an opposite direction into the aluminum coating.   
     
     
         2 . The method in accordance with  claim 1 , wherein the masking includes at least one of adhesives that are heat-resistant below 400° C., synthetics and adhesive metal tapes. 
     
     
         3 . The method in accordance with  claim 2 , wherein the component portions to be coated are cleaned and treated with an activator prior to electro-plating. 
     
     
         4 . The method in accordance with  claim 3 , wherein the activator is nickel chloride. 
     
     
         5 . The method in accordance with  claim 4 , wherein the component for aluminum diffusion heat treating is first heated to approx. 400° to 700° C. and held at this temperature up to two hours, and then further heat-treated for approx. one hour at approx. 1100° C. and then for approx. 5 hours at approx. 1030° C., followed by cooling in undisturbed air. 
     
     
         6 . The method in accordance with  claim 5 , wherein the unmasked portions of the component are coated in the electrolyte to a layer thickness of 5 to 10 μm. 
     
     
         7 . The method in accordance with  claim 6 , wherein the aluminum coating produced by electro-plating is subsequently treated in a pickling bath. 
     
     
         8 . The method in accordance with  claim 1 , wherein the component portions to be coated are cleaned and treated with an activator prior to electro-plating. 
     
     
         9 . The method in accordance with  claim 8 , wherein the activator is nickel chloride. 
     
     
         10 . The method in accordance with  claim 9 , wherein the component for aluminum diffusion heat treating is first heated to approx. 400° to 700° C. and held at this temperature up to two hours, and the further heat-treated for approx. one hour at approx. 1100° C. and then for approx. 5 hours at approx. 1030° C., followed by cooling in undisturbed air. 
     
     
         11 . The method in accordance with  claim 10 , wherein the unmasked portions of the component are coated in the electrolyte to a layer thickness of 5 to 10 μm. 
     
     
         12 . The method in accordance with  claim 11 , wherein the aluminum coating produced by electro-plating is subsequently treated in a pickling bath. 
     
     
         13 . The method in accordance with  claim 1 , wherein the component for aluminum diffusion heat treating is first heated to approx. 400° to 700° C. and held at this temperature up to two hours, and the further heat-treated for approx. one hour at approx. 1100° C. and then for approx. 5 hours at approx. 1030° C., followed by cooling in undisturbed air. 
     
     
         14 . The method in accordance with  claim 13 , wherein the unmasked portions of the component are coated in the electrolyte to a layer thickness of 5 to 10 μm. 
     
     
         15 . The method in accordance with  claim 14 , wherein the aluminum coating produced by electroplating is subsequently treated in a pickling bath. 
     
     
         16 . The method in accordance with  claim 1 , wherein the unmasked portions of the component are coated in the electrolyte to a layer thickness of 5 to 10 μm. 
     
     
         17 . The method in accordance with  claim 16 , wherein the aluminum coating produced by electroplating is subsequently treated in a pickling bath. 
     
     
         18 . The method in accordance with  claim 1 , wherein the aluminum coating produced by electroplating is subsequently treated in a pickling bath. 
     
     
         19 . The method in accordance with  claim 1 , wherein the metallic component is an aircraft gas-turbine component made of a nickel-base alloy