Modified thermal barrier composite coatings

Abstract

A novel coating system is provided that allows for a single coating structure to exhibit properties previously considered mutually exclusive. A unique approach for tailoring specific properties of a coating structure as a function of location within the coating is provided with a specially designed undercoat having a columnar macrostructure and a second coating layer that is selected to be compatible with and complement the undercoat. The resultant composite coating system can maintain thermocomechanical compliance while improving various bulk and/or free surface properties of the composite coating system.

1 . A thermal barrier modified composite coating, comprising:
 a first coating layer bonded to a surface of a substrate, said first coating layer comprising macro columnar features characterized by a predetermined distribution of peaks and valleys at their corresponding free surfaces to create improved mechanical bonding between the first layer and a second layer;   said columnar features derived from a precursor liquid suspension of nano-sized and/or submicron-sized splats to form a thermomechanical compliant interface at the substrate surface, said splats being randomly oriented to produce an isotropic crystallographic orientation for the first coating;   said splats comprising non-equiaxed columnar grains that grow opposite to a direction of heat flow upon cooling to produce an anisotropic crystallographic grain orientation; and wherein said second coating layer is bonded to the corresponding free surfaces of the first coating layer, said second coating layer at the bulk and/or free surface having at least one improved coating property in comparison to the first coating layer.   
     
     
         2 . The thermal barrier modified composite coating of  claim 1 , wherein said coating property is selected from the group consisting of thermal conductivity, erosion resistance, corrosion resistance and thermomechanical compliance. 
     
     
         3 . The thermal barrier modified composite coating of  claim 1 , wherein said first coating layer further comprises built-in porosity in an amount greater than that of the second coating. 
     
     
         4 . The thermal barrier modified composite coating of  claim 1 , wherein said second coating layer is selected from the group consisting of a dense vertically cracked coating, an abradable coating, an environmental barrier coating a densified columnar coating, an atmospheric plasma sprayed coating and any combinations thereof 
     
     
         5 . The thermal barrier modified composite coating of  claim 1 , wherein said substrate comprises a smooth surface. 
     
     
         6 . The thermal barrier modified composite coating of  claim 1 , wherein at least a portion of said peaks and valleys have a width and height substantially non-uniform to form an interfacial boundary with tortuosity. 
     
     
         7 . The thermal barrier modified composite coating of  claim 1 , wherein said coating property is graded in a continuous manner within said second coating layer, wherein said coating property has a first value at first location adjacent to the interface of the first and the second coating layer, said property changing from said first value along a path starting at said first location and extending in a direction towards a point on the free surface of the second coating layer. 
     
     
         8 . The thermal barrier modified composite coating of  claim 1 , wherein said coating property has a first value at a first location adjacent to the surface of the substrate and a second value at a point along a free surface of said second coating layer, wherein said coating property changes from said first value to said second value in a discrete manner. 
     
     
         9 . The thermal barrier modified composite coating of  claim 1 , wherein said first coating layer comprises microstructural features of less than about 25 microns. 
     
     
         10 . The thermal barrier modified composite coating of  claim 1 , wherein said first coating layer comprises microstructural features ranging from about 10 microns to about 50 nm. 
     
     
         11 . A thermal barrier modified composite coating, comprising:
 a first coating layer bonded to a surface of a smooth substrate, said first coating layer having a size less than about 10 μm;   said first coating layer comprising macro columnar features characterized by a predetermined distribution of peaks and valleys at their corresponding free surfaces to create improved mechanical bonding between the first layer and a second layer;   said columnar features derived from a precursor liquid suspension of nano-sized and/or submicron-sized splats to form a thermomechanical compliant interface at the substrate surface, said splats being randomly oriented to produce an isotropic crystallographic orientation for the first coating;   said splats comprising non-equiaxed columnar grains that grow opposite to a direction of heat flow upon cooling to produce an anisotropic crystallographic grain orientation; and   said second layer comprising a densified coating layer bonded to the corresponding free surfaces of the first coating layer, said densified coating having a lower porosity than that of the first coating layer, said densified coating having an improved mechanical erosion barrier in comparison to the first coating layer.   
     
     
         12 . The thermal barrier modified composite coating of  claim 11 , wherein said microstructural features of said first coating layer have a size less than about 10 μm and equal to or greater than about 50 nm. 
     
     
         13 . The thermal barrier modified composite coating of  claim 11 , wherein said densified coating is derived from a second precursor liquid suspension of nano-sized and/or submicron-sized particles. 
     
     
         14 . The thermal barrier modified composite coating of  claim 11 , wherein said predetermined distribution of peaks and valleys are arranged to form an irregular interface having tortuosity. 
     
     
         15 . The thermal barrier modified composite coating of  claim 1 , said first coating layer has built-in porosity in an amount greater than that of the densified coating. 
     
     
         16 . A thermal barrier modified composite coating, comprising:
 a first coating layer bonded to a surface of a smooth substrate, said first coating layer having a size less than about 10 μm;   said first coating layer comprising macro columnar features characterized by a predetermined distribution of peaks and valleys at their corresponding free surfaces to create improved mechanical bonding between the first layer and a second layer;   said columnar features derived from a precursor liquid suspension of nano-sized and/or submicron-sized splats to form a thermomechanical compliant interface at the substrate surface, said splats being randomly oriented to produce an isotropic crystallographic orientation for the first coating;   said splats comprising non-equiaxed columnar grains that grow opposite to a direction of heat flow upon cooling to produce an anisotropic crystallographic grain orientation; and   said second layer comprising a densified coating layer bonded to the corresponding free surfaces of the first coating layer, said densified coating having a lower porosity than that of the first coating layer, said densified coating derived from a dry powder applied by atmospheric spraying, said coating comprising partially molten and fully molten particles having an improved mechanical erosion barrier in comparison to the first coating layer.   
     
     
         17 . The thermal barrier modified composite coating of  claim 16 , wherein said particles of the densified coating layer have a size greater than about 10 μm. 
     
     
         18 . The thermal barrier modified composite coating of  claim 16 , wherein said smooth substrate has a Ra of less than about 125 μin. 
     
     
         19 . The thermal barrier modified composite coating of  claim 18 , wherein said smooth substrate has a Ra of less than about 80 pin. 
     
     
         20 . The thermal barrier modified composite coating of  claim 16 , wherein said densified coating layer comprises at least one improved coating property in comparison to the first coating layer and further wherein said improved coating property is graded. 
     
     
         21 . The thermal barrier modified composite coating of  claim 16 , wherein said densified coating layer produces a densely vertically cracked microstructure.