Method for forming binder-free refractory carbide, nitride and boride coatings with a controlled porosity

Abstract

The present invention is directed to methods for formation of refractory carbide, nitride, and boride coatings without use of a binding agent. The present invention is directed to methods of creating refractory coatings with controlled porosity. Refractory coatings can be formed from refractory metal, metal oxide, or metal/metal oxide composite refractory coating precursor of the 9 refractory metals encompassed by groups 4-6 and periods 4-6 of the periodic table; non-metallic elements (e.g. Si & B) and their oxides (i.e. SiO 2 & B 2 O 3 ) are also pertinent. The conversion of the refractory coating precursor to refractory carbide, nitride or boride is achieved via carburization, nitridization, or boridization in the presence of carbon-containing (e.g. CH 4 ), nitrogen containing (e.g. NH 3 ), and boron-containing (e.g. B 2 H 6 ) gaseous species. Any known technique of applying the refractory coating precursor can be used. The porosity of resultant refractory coatings is controlled through compositional manipulation of composite refractory coating precursors.

1 . A method of forming a refractory coating comprising:
 applying a refractory coating precursor to a surface using any known method such as spray techniques;   introducing a gaseous species; and   generating thermal decomposition of the gaseous species.   
     
     
         2 . The method of  claim 1  further comprising using one of a group consisting of refractory metal, metal oxide, and metal/metal oxide composite as a refractory coating precursor. 
     
     
         3 . The method of  claim 1  further comprising using one selected from a group consisting of carbon-containing, nitrogen-containing, and boron containing gaseous species. 
     
     
         4 . The method of  claim 1  further comprising using plasma spray. 
     
     
         5 . The method of  claim 1  further comprising using cold spray. 
     
     
         6 . The method of  claim 1  further comprising forming one of a group consisting of refractory carbide, nitride, and boride coatings or any combination thereof. 
     
     
         7 . A refractory coating with increased hardness and decreased porosity comprising:
 a refractory coating precursor applied with spray techniques; and   a gaseous species configured to be thermally decomposable such that the refractory coating precursor is converted into a refractory coating with increased hardness and decreased porosity.   
     
     
         8 . The refractory coating of  claim 7  wherein the refractory coating precursor is one chosen from a group consisting of refractory metal, metal oxide, and metal/metal oxide composite. 
     
     
         9 . The refractory coating of  claim 7  wherein the gaseous species is one selected from a group consisting of carbon-containing, nitrogen-containing, and boron containing gaseous species. 
     
     
         10 . The refractory coating of  claim 7  wherein spray techniques comprises plasma spray. 
     
     
         11 . The refractory coating of  claim 7  wherein spray techniques comprises cold spray. 
     
     
         12 . The refractory coating of  claim 7  wherein the refractory coating is one selected from a group consisting of refractory carbide, nitride, and boride coatings or any combination thereof. 
     
     
         13 . The refractory coating of  claim 7  wherein porosity is controlled by compositional manipulation of composite refractory coating precursors. 
     
     
         14 . A method of forming a refractory coating comprising:
 applying a refractory coating precursor to a surface using any known technique such as thermal spray;   introducing a gaseous species;   generating thermal decomposition of the gaseous species resulting in the refractory coating defining a porous refractory matrix; and   using the porous refractory matrix as a scaffold for the formation of a multi-functional coating.   
     
     
         15 . The method of  claim 14  further comprising using one of a group consisting of refractory metal, metal oxide, and metal/metal oxide composite as a refractory coating precursor. 
     
     
         16 . The method of  claim 14  further comprising using plasma spray. 
     
     
         17 . The method of  claim 14  further comprising using one or more gaseous species selected from a group consisting of carbon-containing, nitrogen-containing, and boron containing gaseous species. 
     
     
         18 . The method of  claim 14  further comprising forming one of a group consisting of refractory carbide, nitride, and boride coatings, or any combination thereof. 
     
     
         19 . The method of  claim 14  further comprising creating the multi-functional coating using any known void-filling technique such as ambient-temperature sealing with organic sealants, filling with sol-gel processed inorganic ceramics, and liquid metal infiltration which requires significantly higher temperatures. 
     
     
         20 . A binder-free refractory coating with a controlled porosity comprising:
 a refractory coating precursor applied with thermal spray;   a gaseous species configured to be thermally decomposable such that the refractory coating precursor is converted into a refractory coating with a controlled porosity; and   a porous refractory matrix that serves as a multi-functional coating.   
     
     
         21 . The refractory coating of  claim 20  wherein the refractory coating precursor is one chosen from a group consisting of refractory metal, metal oxide, and metal/metal oxide composite. 
     
     
         22 . The refractory coating of  claim 20  wherein the gaseous species is one or more selected from a group consisting of carbon-containing, nitrogen-containing, and boron containing gaseous species. 
     
     
         23 . The refractory coating of  claim 20  wherein thermal spray comprises plasma spray. 
     
     
         24 . The refractory coating of  claim 20  wherein the refractory coating is one selected from a group consisting of refractory carbide, nitride, and boride coatings, or any combination thereof. 
     
     
         25 . The refractory coating of  claim 20  wherein porosity is controlled by compositional manipulation of composite refractory coating precursors. 
     
     
         26 . The refractory coating of  claim 20  further comprising the porous refractory matrix treated with one or more selected from a group of ambient-temperature sealing with organic sealants, filling with sol-gel processed inorganic ceramics, and liquid metal infiltration which requires significantly higher temperatures.