Additive method enabling air plasma spray (aps) over a smooth surface

Abstract

A stacked up structure can include a first environmental barrier coating (EBC) layer and a second EBC layer. A first process can be used to form the first layer and a second process can be used to form the second layer. In one embodiment interfacial material can be formed for improved bonding of the second layer to the first layer. The interfacial material can define a continuous or discontinuous layer of nonuniform thickness.

1 . A stacked up structure comprising:
 a first rare earth disilicate layer;   a second rare earth disilicate layer; and   interfacial material defining a bond surface on which the second rare earth disilicate layer is bonded, said interfacial material formed between the first rare earth disilicate layer and the second rare earth disilicate layer,   wherein a roughness of the bond surface is greater than a roughness of a surface for bonding the second rare earth disilicate layer in an absence of the interfacial material.   
     
     
         2 . The stacked up structure of  claim 1 , wherein the interfacial material is formed on the first rare earth disilicate layer. 
     
     
         3 . The stacked up structure of  claim 1 , wherein the interfacial material comprises particles at least partially embedded in the first rare earth disilicate layer. 
     
     
         4 . The stacked up structure of  claim 1 , further having a bond coat layer below the first rare earth disilicate layer. 
     
     
         5 . The stacked up structure of  claim 1 , wherein the interfacial material defines a continuous layer formed on the first rare earth disilicate layer. 
     
     
         6 . The stacked up structure of  claim 1 , wherein the interfacial material defines a discontinuous layer formed on the first rare earth disilicate layer. 
     
     
         7 . The stacked up structure of  claim 1 , wherein the first rare earth disilicate layer includes a sintered microstructure, and wherein the second rare earth disilicate layer includes a splat microstructure. 
     
     
         8 . The stacked up structure of  claim 1 , wherein a length of a bond line defined at the bond surface in a cross section projection of the stacked up structure is more than 20 percent longer than a bond line defined at the surface for bonding in the cross sectional projection of the stacked up structure. 
     
     
         9 . The stacked up structure of  claim 1 , wherein the interfacial material has an average thickness of less than 50 percent of an average thickness of the first rare earth disilicate layer. 
     
     
         10 . The stacked up structure of  claim 1 , wherein the bond surface is defined by the interfacial material. 
     
     
         11 . The stacked up structure of  claim 1 , wherein the bond surface is defined by the interfacial material and the first rare earth disilicate layer. 
     
     
         12 . The stacked up structure of  claim 1 , wherein the stacked up structure includes a CMC substrate, wherein the first rare earth disilicate layer is formed over the CMC substrate. 
     
     
         13 . A method comprising:
 forming a first rare earth disilicate layer on a surface;   forming interfacial material on the first rare earth disilicate layer to define a bond surface; and   forming a second rare earth disilicate layer on the bond surface, wherein the forming interfacial material results in the bond surface having a roughness greater than a roughness of a surface for bonding of the second rare earth disilicate layer in an absence of the interfacial material.   
     
     
         14 . The method of  claim 13 , wherein the forming a first rare earth disilicate layer includes using a first process and wherein the forming a second rare earth disilicate layer includes using a second process. 
     
     
         15 . The method of  claim 13 , wherein the bond surface is defined by the interfacial material. 
     
     
         16 . The method of  claim 13 , wherein the bond surface is defined by the interfacial material and the first rare earth disilicate layer. 
     
     
         17 . The method of  claim 13 , wherein the forming interfacial material includes using an additive process. 
     
     
         18 . The method of  claim 13 , wherein the forming interfacial material is performed so that the interfacial material defines a continuous layer. 
     
     
         19 . The method of  claim 13 , wherein the forming interfacial material is performed so that the interfacial material defines a discontinuous layer. 
     
     
         20 . The method of  claim 13 , wherein the forming interfacial material includes using spray evaporating. 
     
     
         21 . The method of  claim 13 , wherein the forming interfacial material includes sprinkling particles onto the first rare earth disilicate layer with the rare earth disilicate layer in a wet state. 
     
     
         22 . The method of  claim 13 , wherein the forming interfacial material includes sprinkling particles onto the first rare earth disilicate layer, wherein the particles include agglomerates of particles. 
     
     
         23 . The method of  claim 13 , wherein the forming a first rare earth disilicate layer includes forming a slurry, and wherein the forming a second rare earth disilicate layer includes using an air plasma spray (APS) process. 
     
     
         24 . The method of  claim 13 , wherein the first rare earth disilicate layer includes a sintered microstructure, and wherein the second rare earth disilicate layer includes a splat microstructure. 
     
     
         25 . The method of  claim 13 , wherein the forming a first rare earth disilicate layer on a surface includes forming the first rare earth disilicate layer over a CMC substrate. 
     
     
         26 . A stacked up structure comprising:
 a plurality of rare earth material layers defining an environmental barrier coating (EBC);   a first vertical cross section extending through one or more layers of the plurality of rare earth material layers, the first vertical cross section having a first layer profile; and   a second vertical cross section extending through one or more layers of the plurality of rare earth material layers, the second vertical cross section having a second layer profile.   
     
     
         27 . The stacked up structure of  claim 26 , wherein the second layer profile is absent a layer included in the first layer profile. 
     
     
         28 . The stacked up structure of  claim 26 , wherein the second layer profile is absent a plurality of layers included in the first layer profile. 
     
     
         29 . The stacked up structure of  claim 26 , wherein the second layer profile is absent a layer included in the first layer profile, and wherein the first layer profile and the second layer profile include a common top layer. 
     
     
         30 . The stacked up structure of  claim 26 , wherein the stacked up structure defines an article selected from the group consisting of an airfoil, a shroud, a blade, a vane, a nozzle, a turbine center frame, a cowl, an exhaust mixer. 
     
     
         31 . The method of  claim 13  wherein the forming the first rare earth disilicate layer comprises depositing an aerosol slurry of the first rare earth disilicate, and wherein the forming interfacial material comprises spraying a slurry of the interfacial material onto the first rare earth disilicate or depositing particles of the interfacial material onto the first rare earth disilicate layer, and wherein the forming the second rare earth disilicate layer comprises air plasma spraying the second rare earth disilicate.