Interference colored titanium with protective oxide film

Abstract

Coatings for titanium and titanium alloy substrates are described. The coatings can include an aluminum oxide layer and, in some cases, a thin titanium oxide layer. If the coating includes a titanium oxide layer, the aluminum oxide layer can cover and protect the titanium oxide layer from abrasion and scratching. In some examples, the titanium oxide layer has a thickness sufficient to provide a color by thin-film interference, which can be visible through the overlying aluminum oxide layer. In some embodiments, the aluminum oxide layer is colorized using an anodic dye, pigment or metal colorant, which can combine with interference colors of the titanium oxide layer.

What is claimed is: 
     
         1 . A part, comprising:
 a substrate composed of titanium or a titanium alloy; and   a coating disposed on the substrate, the coating including an aluminum oxide layer.   
     
     
         2 . The part of  claim 1 , wherein the coating includes a titanium oxide layer. 
     
     
         3 . The part of  claim 2 , wherein the aluminum oxide layer is more porous than the titanium oxide layer. 
     
     
         4 . The part of  claim 2 , wherein the titanium oxide layer has a thickness ranging from about 20 nm to about 150 nm. 
     
     
         5 . The part of  claim 2 , wherein the titanium oxide layer imparts a color to the coating via thin film interference coloring. 
     
     
         6 . The part of  claim 2 , wherein the aluminum oxide layer has a colorant infused within pores of the aluminum oxide layer. 
     
     
         7 . The part of  claim 1 , wherein the aluminum oxide layer has a colorant infused within pores of the aluminum oxide layer. 
     
     
         8 . The part of  claim 1 , wherein the aluminum oxide layer has a hardness of about 300 HV or greater. 
     
     
         9 . The part of  claim 1 , wherein the coating includes a layer of aluminum or aluminum alloy between the aluminum oxide layer and the substrate. 
     
     
         10 . The part of  claim 1 , wherein the aluminum oxide layer has a thickness ranging from about 5 micrometers to about 20 micrometers. 
     
     
         11 . A method of forming a coating on a substrate, the substrate composed of titanium or a titanium alloy, the method comprising:
 depositing a layer of aluminum or an aluminum alloy on the substrate; and   converting at least a portion of the layer of aluminum or the aluminum alloy to an aluminum oxide layer.   
     
     
         12 . The method of  claim 11 , wherein substantially all of the layer of aluminum or aluminum alloy is converted to the aluminum oxide layer. 
     
     
         13 . The method of  claim 12 , wherein at least a portion of the substrate is converted to a titanium oxide layer. 
     
     
         14 . The method of  claim 13 , wherein the aluminum oxide layer is more porous than the titanium oxide layer. 
     
     
         15 . The method of  claim 13 , wherein the titanium oxide layer has a thickness ranging from about 20 nm to about 150 nm. 
     
     
         16 . The method of  claim 11 , further comprising infusing a colorant within pores of the aluminum oxide layer. 
     
     
         17 . An enclosure for an electronic device, the enclosure comprising:
 a substrate composed of titanium or a titanium alloy, the substrate having a coating corresponding to an outer surface of the enclosure, the coating including an aluminum oxide layer.   
     
     
         18 . The enclosure of  claim 17 , wherein the coating includes a titanium oxide layer. 
     
     
         19 . The enclosure of  claim 18 , wherein the titanium oxide layer has a thickness ranging from about 20 nm to about 150 nm. 
     
     
         20 . The enclosure of  claim 19 , wherein the enclosure includes a first portion that is interference colored and a second portion that is not interference colored, wherein the titanium oxide layer is part of the first portion.