Methods of protecting aerospace components against corrosion and oxidation

Abstract

Embodiments of the present disclosure generally relate to protective coatings on an aerospace component and methods for depositing the protective coatings. In one or more embodiments, a method for depositing a coating on an aerospace component includes depositing one or more layers on a surface of the aerospace component using an atomic layer deposition or chemical vapor deposition process, and performing a partial oxidation and annealing process to convert the one or more layers to a coalesced layer having a preferred phase crystalline assembly. During oxidation cycles, an aluminum depleted region is formed at the surface of the aerospace component, and an aluminum oxide region is formed between the aluminum depleted region and the coalesced layer. The coalesced layer forms a protective coating, which decreases the rate of aluminum depletion from the aerospace component and the rate of new aluminum oxide scale formation.

What is claimed is: 
     
         1 . A method for depositing a coating on an aerospace component, comprising:
 exposing an aerospace component to a first precursor and a first reactant to form a first deposited layer on a surface of the aerospace component by a first atomic layer deposition (ALD) process at a temperature between about 20° C. to about 500° C., the aerospace component comprising a metal,   wherein the first deposited layer forms a protective coating on the aerospace component, and   wherein the protective coating protects the aerospace component from corrosion and oxidation and decreases a rate of depletion of the metal from the aerospace component; and   annealing and oxidizing the protective coating on the aerospace component to convert the protective coating into a crystalline form, wherein the protective coating in the crystalline form strengthens the protective coating.   
     
     
         2 . The method of  claim 1 , wherein the metal comprises a steel. 
     
     
         3 . The method of  claim 1 , wherein the annealing and oxidizing is done at a temperature between about 800° C. to about 1500° C., and wherein the oxidation process may partially oxidize the protective coating. 
     
     
         4 . The method of  claim 1 , further comprising:
 sequentially exposing the aerospace component to the first precursor and the first reactant to form the first deposited layer.   
     
     
         5 . The method of  claim 1 , further comprising:
 exposing the aerospace component to a second precursor and a second reactant to form a second deposited layer on the first deposited layer by a second ALD process or a chemical vapor deposition (CVD) process prior to annealing the first deposited layer, wherein the first deposited layer and the second deposited layer have different compositions from each other,   wherein annealing and oxidizing the first deposited layer further comprises simultaneously annealing and oxidizing the second deposited layer to form a coalesced layer.   
     
     
         6 . The method of  claim 5 , wherein the first deposited layer comprises aluminum oxide, hafnium doped aluminum oxide, yttrium-doped aluminum oxide, or silicon-doped aluminum oxide. 
     
     
         7 . The method of  claim 1 , wherein the second deposited layer comprises silicon or yttrium. 
     
     
         8 . The method of  claim 5 , further comprising:
 repeating the exposure of the aerospace component to the first precursor and the first reactant to form a third deposited layer on the second deposited layer prior to annealing the first deposited layer and the second deposited layer;   repeating the exposure of the aerospace component to the second precursor and the second reactant to form a fourth deposited layer on the third deposited layer;   repeating the exposure of the aerospace component to the first precursor and the first reactant to form a fifth deposited layer on the fourth deposited layer; and   annealing and oxidizing the first, second, third, fourth, and fifth deposited layers to form a coalesced layer.   
     
     
         9 . The method of  claim 1 , wherein the first deposited layer comprises chromium oxide, and wherein annealing the first deposited layer forms a coalesced layer comprising chromium oxide, aluminum oxide, and a mixed chromium-aluminum oxide. 
     
     
         10 . A method for depositing a coating on an aerospace component, comprising:
 depositing a first deposited layer on a surface of an aerospace component by a chemical vapor deposition (CVD) process, the aerospace component comprising a metal;   converting the first deposited layer to a crystalline phase; and   forming a metal oxide region between the first deposited layer and the aerospace component, the metal oxide region having a crystalline assembly,   wherein the first deposited layer and the metal oxide region form a protective coating on the aerospace component, and   wherein the protective coating protects the aerospace component from corrosion and oxidation and decreases a rate of depletion of the metal from the aerospace component.   
     
     
         11 . The method of  claim 10 , further comprising:
 depositing a second deposited layer on the first deposited layer by a second CVD process or an atomic layer deposition (ALD) process prior to converting the first deposited layer to a crystalline phase,   wherein the first deposited layer and the second deposited layer have different compositions from each other, and   wherein converting the first deposited layer to a crystalline phase further comprises forming a coalesced layer having the crystalline phase.   
     
     
         12 . The method of  claim 11 , wherein the first deposited layer comprises aluminum oxide, hafnium-doped aluminum oxide, yttrium-doped aluminum oxide, or silicon-doped aluminum oxide. 
     
     
         13 . The method of  claim 11 , further comprising:
 depositing one or more additional deposited layers on the second deposited layer prior to converting the first and second deposited layers to the crystalline phase; and   converting the first deposited layer, the second deposited layer, and the one or more additional deposited layers to a coalesced layer having a crystalline phase.   
     
     
         14 . The method of  claim 10 , wherein the first deposited layer comprises chromium oxide, and wherein forming the aluminum oxide region forms a coalesced layer comprising chromium oxide, aluminum oxide, and a mixed chromium-aluminum oxide. 
     
     
         15 . The method of  claim 14 , wherein the first deposited layer is deposited at a temperature of about 300° C. to about 1100° C. 
     
     
         16 . The method of  claim 10 , wherein the metal oxide region is formed by annealing the first deposited layer at a temperature between about 500° C. to about 1100° C. for a time period of about 1 hour to about 15 hours. 
     
     
         17 . A method for depositing a coating on an aerospace component, comprising:
 depositing a first deposited layer on a surface of an aerospace component by a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process, the aerospace component comprising a metal;   performing a first annealing and oxidizing process to convert the first deposited layer into a preferred crystalline phase;   depositing a second deposited layer by the CVD process or the ALD process on the first deposited layer; and   performing a second annealing and oxidizing process to convert the second deposited layer into the preferred crystalline phase,   wherein the first deposited layer and the second deposited layer form a protective coating on the aerospace component, and   wherein the protective coating protects the aerospace component from corrosion and oxidation and decreases a rate of depletion of the metal from the aerospace component.   
     
     
         18 . The method of  claim 17 , wherein the second deposited layer comprises aluminum oxide, hafnium-doped aluminum oxide, yttrium-doped aluminum oxide, or silicon-doped aluminum oxide. 
     
     
         19 . The method of  claim 17 , a metal oxide region is formed between the first deposited layer and the aerospace component, the metal oxide region having a crystalline assembly. 
     
     
         20 . The method of  claim 17 , wherein the first deposited layer comprising aluminum, wherein the second deposited layer comprises chromium, and wherein the first annealing and oxidation process and the second annealing and oxidizing process are performed at a temperature between about 500° C. to about 1200° C. for a time period of about 1 hour to about 15 hours in air.