Cmas resistant thermal barrier coatings

Abstract

The present application provides Calcia-Magnesia-Alumina-Silica (CMAS) (or molten silicate) resistant thermal barrier coatings (IBC). The coatings include elongate growth domains of non-equiaxed, randomly arranged overlapping grains or splats. The elongate growth domains include overlapping individual, randomly distributed splats of tough and soft phases. In some embodiments, the elongate growth domains are formed via air plasma spray. In some embodiments, the tough phases are at least partially stabilized zirconia and/or hafnia compositions, and the soft phases are CMAS (or molten silicate) reactive or resistant compositions. Within each elongate growth domain, the mixture of the tough and soft phases act together to limit penetration of CMAS and also provide sufficient domain toughness to minimize cracking forces produced during crystallization of infiltrated CMAS. The soft phases may react with the CMAS and increase its melting point, increase its viscosity, and reduce the destabilization of the tough phases.

1 .- 19 . (canceled) 
     
     
         20 . A method of forming a thermal barrier coating on a substrate, the method comprising:
 obtaining a substrate;   obtaining a feedstock consisting of about micron or sub-micron ceramic particles of tough and soft phases suspended in a liquid agent, wherein the tough phases are at least one of partially stabilized zirconia compositions and partially stabilized hafnia compositions, and the soft phases are at least one of CMAS reactive compositions and CMAS resistant compositions; and   utilizing an air plasma spray apparatus to heat and deposit the tough and soft phases of the feedstock on the substrate in randomly distributed overlapping splats that form a plurality of elongate material growth domains of at least about 75% density defined between domain boundaries.   
     
     
         21 . The method of  claim 20 , wherein at least about 75% of the splats of the domains include a width to length aspect ratio of greater than or equal to about 3:1 and a substantially isotropic crystallographic orientation. 
     
     
         22 . The method of  claim 21 , wherein the widths of the splats are oriented within the range of about 45 degrees to about 90 degrees with respect to the direction in which the tough and soft phases are deposited on the substrate from the air plasma spray apparatus. 
     
     
         23 . The method of  claim 20 , wherein the tough phases are stabilized by at least one of yttria, magnesia, calcia, ceria, lanthana, neodymia, europia, gadolinia, erbia, dysprosia, ytterbia, scandia, samaria and lutetia, and wherein the soft phases are molten silicate resistant compositions. 
     
     
         24 . The method of  claim 20 , wherein the feedstock is a mixture of the tough and soft phase, and wherein utilizing an air plasma spray apparatus to heat and deposit the tough and soft phases of the feedstock on the substrate includes introducing the mixture into a plasma plume of the air plasma spray apparatus. 
     
     
         25 . The method of  claim 20 , wherein the feedstock includes a first distinct feedstock including the tough phases and a second distinct feedstock including the soft phases, and wherein utilizing an air plasma spray apparatus to heat and deposit the tough and soft phases of the feedstock on the substrate includes introducing the first and second feedstocks into a plasma plume of the air plasma spray apparatus at the same time.