SELECTIVE OXIDATION OF A MODIFIED MCrAIY COMPOSITION LOADED WITH HIGH LEVELS OF CERAMIC ACTING AS A BARRIER TO SPECIFIC OXIDE FORMATIONS

Abstract

A composition based on a novel MCrAlY formulation is provided for the production of protective coatings. The specific combination of the constituents of the MCrAlY formulation advantageously allows significantly high loadings of ceramic (metal oxide) while still retaining the ability to selectively oxidize aluminum to form alumina scale, a property previously not attainable with conventional MCrAlY materials when loaded with ceramics at levels of 15-45 weight percent. The alumina scale in combination with the modified MCrAlY formulation act as a barrier to specific detrimental oxide formations. The compositions of the present invention can act as protective coatings for a wide array of applications.

1 . A method of applying a protective coating, comprising the steps of:
 (i) a modified MCrAlY formulation, the formulation characterized by an absence of silicon and hafnium, wherein
 M comprises Co in an amount of about 45 to about 75 weight percent (wt %), Ni is an amount of 0 to about 12 wt % and Fe is in an amount of 0 to about 12 wt %; 
 Cr is in an amount of about 15-25 wt %; 
 Y is in an amount of about 0.1-1.0 wt %; 
 Al is in an amount of 5-10 wt %; 
 Nb is in an effective amount of 6-15 wt %; and 
 O is in an amount of about 1-4 wt %; and 
   (ii) applying the modified MCrAlY formulation onto a substrate in a oxidizing environment with air plasma spray (APS) or a high velocity detonation gun; and   (iii) selectively oxidizing Al as a protective alumina scale overlying the coating.   
     
     
         2 . The method of  claim 1 , wherein the step of depositing the formulation is performed by air plasma spraying. 
     
     
         3 . The method of  claim 1 , wherein the substrate includes aviation turbine components, furnace roll or industrial gas turbine components. 
     
     
         4 . The method of  claim 1 , further comprising blending a ceramic material into the modified MCrAlY formulation. 
     
     
         5 . The method of  claim 4 , wherein the ceramic material is a metal oxide selected from the group consisting alumina, alumina doped with other metal ions, zirconia, aluminosilicates. yttria, yttria stabilized zirconia, magnesia stabilized zirconia, zircon, silica, zirconia toughened alumina, mullite, and combinations thereof. 
     
     
         6 . The method of  claim 5 , wherein the ceramic material is alumina in an amount of about 18 to about 32%.