Adhesion of thermal spray coatings over a smooth surface

Abstract

A coated component is generally provided, along with methods of forming such a coating system. The coated component includes a substrate having a surface with a coating system thereon. The coating system may include a columnar thermal barrier coating (TBC) over the surface of the substrate, with the columnar TBC including surface-connected voids. An intermediate layer is over the columnar TBC layer. The intermediate layer has a surface opposite of the columnar TBC that is rougher than the surface of the columnar TBC. A second TBC is over the intermediate layer.

1 . A coated component comprising a substrate having a surface with a coating system thereon, wherein the coating system comprises:
 a columnar thermal barrier coating (TBC) over the surface of the substrate, wherein the columnar TBC includes surface-connected voids, and wherein the columnar TBC has a surface opposite of the substrate;   an intermediate layer directly on the surface of the columnar TBC layer, wherein the intermediate layer has a surface opposite of the columnar TBC that is rougher than the surface of the columnar TBC; and   a second TBC directly on the surface of the intermediate layer.   
     
     
         2 . The coating component of  claim 1 , wherein the surface-connected voids are substantially vertically oriented. 
     
     
         3 . The coating component of  claim 1 , wherein a majority of the surface-connected voids extend through the entire thickness of the columnar TBC. 
     
     
         4 . The coating component of  claim 1 , wherein the surface-connected voids of the columnar TBC are defined by grain boundaries within the columnar TBC. 
     
     
         5 . The coating component of  claim 1 , wherein the second TBC has a porosity, and wherein the intermediate layer has a porosity that is less than the porosity of the second TBC. 
     
     
         6 . The coating component of  claim 1 , wherein the intermediate layer has a porosity of about 0.1% to about 10%, and wherein the second TBC has a porosity of about 10% to about 25%. 
     
     
         7 . The coating component of  claim 1 , wherein the columnar TBC has a thickness, and wherein the intermediate layer has a thickness that is about 1% to about 50% of the thickness of the columnar TBC. 
     
     
         8 . The coating component of  claim 1 , wherein the coating system further comprises a bond coating on the surface of the substrate such that the bond coating is present between the columnar TBC and the surface of the substrate. 
     
     
         9 . The coating component of  claim 8 , wherein a thermally grown oxide layer is on the bond coating between the bond coating and the columnar TBC. 
     
     
         10 . The coating component of  claim 1 , wherein the surface of the intermediate layer has a surface roughness (Ra) that is about 2 μm or greater. 
     
     
         11 . The coating component of  claim 1 , wherein the surface of the intermediate layer has a surface roughness (Ra) that is about 2.5 μm to about 6.5 μm. 
     
     
         12 . The coating component of  claim 1 , wherein the surface of the columnar TBC has a surface roughness (Ra) that is about 2.5 μm or less in the areas excluding the space formed by the voids. 
     
     
         13 . The coating component of  claim 1 , wherein the surface of the columnar TBC has a surface roughness (Ra) that is about 2 μm or less in the areas excluding the space formed by the voids. 
     
     
         14 . The coating component of  claim 1 , wherein the columnar TBC comprises a ceramic material, and wherein the intermediate layer comprises a ceramic material deposited via air plasma spray. 
     
     
         15 . The coating component of  claim 1 , wherein the substrate comprises a metal or a metal alloy. 
     
     
         16 . A method of forming a coating system on a surface of a substrate, the method comprising:
 forming a columnar thermal barrier coating (TBC) over the surface of the substrate, wherein the columnar TBC has surface-connected voids, and wherein the columnar TBC has a surface with a first surface roughness; and   forming an air plasma spray (APS) intermediate layer directly onto the columnar TBC, wherein the intermediate layer has a surface opposite of the columnar TBC that has a second surface roughness that is rougher than the first surface roughness of the columnar TBC.   
     
     
         17 . The method of  claim 16 , wherein the surface-connected voids are substantially vertically oriented, and wherein the surface of the columnar TBC has a surface roughness (Ra) that is about 2.5 μm or less in the areas excluding the space formed by the voids; and wherein the surface of the intermediate layer has a surface roughness (Ra) that is about 2.5 μm or greater. 
     
     
         18 . The method of  claim 16 , wherein forming the APS intermediate layer comprises:
 spraying, via a plasma spray torch, a plurality of fully melted microparticles onto the surface of the columnar TBC such that the APS intermediate layer has a porosity that is about 10% or less, wherein the microparticles comprise a ceramic TBC layer material.   
     
     
         19 . The method of  claim 16 , further comprising:
 forming a second TBC directly over the APS intermediate layer.   
     
     
         20 . The method of  claim 19 , wherein forming a second TBC over the APS intermediate layer comprises:
 spraying, via a plasma spray torch, a plurality of partially melted microparticles onto the surface of the columnar TBC such that the second TBC has a porosity of about 10% to about 25%, wherein the microparticles comprise a ceramic TBC layer material.