Thermo-Mechanical Fatigue Resistant Aluminum Abradable Coating

Abstract

An aluminum coating to be deposited on a substrate having a first coefficient of thermal expansion has an aluminum matrix, and particles of a material having a low coefficient of thermal expansion incorporated into the matrix. The particles bond sufficiently well to the aluminum matrix to carry a portion of the mechanical load.

What is claimed is: 
     
         1 . An aluminum coating to be deposited on a substrate having a first coefficient of thermal expansion, said aluminum coating comprising:
 an aluminum matrix;   particles of a material having a low coefficient of thermal expansion incorporated into said matrix; and   said particles bonding sufficiently well to the aluminum matrix to carry a portion of a mechanical load.   
     
     
         2 . The aluminum coating of  claim 1 , wherein said particles are selected from the group consisting of carbides, borides, oxides, and combinations thereof. 
     
     
         3 . The aluminum coating of  claim 1 , wherein said particles are aluminum boride particles. 
     
     
         4 . The aluminum coating of  claim 1 , wherein said particles are titanium boride particles. 
     
     
         5 . The aluminum coating of  claim 4 , wherein said titanium boride particles have a ratio of titanium to boron in the range of 1:1 to 1:4. 
     
     
         6 . The aluminum coating of  claim 1 , wherein said particles are present in an amount from 1.0 to 33 vol %. 
     
     
         7 . The aluminum coating of  claim 1 , wherein said particles are present in an amount of from 10 to 25 vol %. 
     
     
         8 . The aluminum coating of  claim 1 , wherein said particles are present in an amount of 15 to 20 vol %. 
     
     
         9 . The aluminum coating of  claim 1 , further comprising a pore making material. 
     
     
         10 . The aluminum coating of  claim 9 , wherein said pore making material is selected from the group consisting of hexagonal boron nitride, polyester and Lucite. 
     
     
         11 . A process for applying an aluminum coating to a part comprising the steps of:
 providing a part;   forming a powder containing an aluminum matrix and particles having a low coefficient of thermal expansion bonded to said aluminum matrix; and   thermally spraying said powder onto said part.   
     
     
         12 . The process of  claim 11 , wherein said part providing step comprises providing a part formed from a titanium based alloy or an iron based alloy. 
     
     
         13 . The process of  claim 11 , wherein said powder forming step comprises forming a powder containing particles selected from the group consisting of oxide material, a carbide, a boride, and combinations thereof. 
     
     
         14 . The process of  claim 13 , wherein said powder forming step comprises forming said powder to have from 1.0 to 33 vol % of said particles. 
     
     
         15 . The process of  claim 13 , wherein said powder forming step comprises forming said powder to have from 10 to 25 vol % of said particles. 
     
     
         16 . The process of  claim 13 , wherein said powder forming step comprises forming said powder to have from 15 to 20 vol % of said particles. 
     
     
         17 . The process of  claim 13 , wherein said powder forming step comprises using titanium boride particles. 
     
     
         18 . The process of  claim 13 , wherein said powder forming step comprises using aluminum boride particles. 
     
     
         19 . The process of  claim 11 , further comprises adding a pore making material to said powder. 
     
     
         20 . The process of  claim 11 , wherein said powder forming step comprises melt atomization of a boride containing aluminum alloy and quenching the boride containing aluminum alloy during atomization to form particles of a metastable solid solution. 
     
     
         21 . The process of  claim 11 , further comprising subjecting said aluminum coating to a heat treatment in the range of from 625 to 650 degrees Centigrade for 2.0 hours. 
     
     
         22 . A process for forming an aluminum alloy matrix containing fine particles comprising the steps of:
 melt atomizing a boride containing aluminum alloy; and   quenching the boride containing aluminum alloy during atomization to form particles of a metastable solid solution.