Techniques for depositing coating on ceramic substrate

Abstract

A method of coating a substrate, the method including depositing mullite on the substrate during a first time period via thermal spraying to form a first layer, the mullite comprising mullite powder formed via at least one of a fused plus crush or sinter plus crush process; and depositing a second material on the first layer to form a second layer, wherein the substrate is at a temperature less than approximately 50 degrees Celsius at approximately a beginning of the first time period. In some embodiments, the method may further include depositing silicon to form a silicon bond layer between the substrate and mullite layer.

1 . A method of coating a substrate, the method comprising:
 depositing mullite on the substrate during a first time period via thermal spraying to form a first layer, the mullite comprising mullite powder formed via at least one of a fused plus crush or sinter plus crush process; and   depositing a second material on the first layer to form a second layer,   wherein the substrate is at a temperature less than approximately 50 degrees Celsius at approximately a beginning of the first time period.   
     
     
         2 . The method of  claim 1 , wherein the temperature of the substrate is less than approximately 40 degrees Celsius at approximately the beginning of the first time period. 
     
     
         3 . The method of  claim 1 , further comprising maintaining the substrate at a temperature less than approximately 200 Celsius throughout the first time period. 
     
     
         4 . The method of  claim 1 , wherein the first layer comprises crystalline mullite substantially immediately following the deposition of the mullite. 
     
     
         5 . The method of  claim 1 , further comprising depositing silicon on the substrate to form a silicon layer before depositing the mullite on the substrate. 
     
     
         6 . The method of  claim 5 , further comprising heat treating the silicon layer prior to depositing the mullite. 
     
     
         7 . The method of  claim 6 , wherein heat treating the silicon layer comprises heat treating the silicon layer at a temperature of about 800 degrees Celsius to about 1250 degrees Celsius for about 0.2 hours to about 4 hours. 
     
     
         8 . The method of  claim 1 , wherein the second layer comprises at least one of barium strontium aluminum silicate (BSAS), ytterbium mono-silicate or ytterbium di-silicate. 
     
     
         9 . The method of  claim 1 , wherein the first layer has a thickness of approximately 1 mil to approximately 6 mils. 
     
     
         10 . The method of  claim 1 , wherein the second layer has a thickness of approximately 2 mils to approximately 15 mils. 
     
     
         11 . The method of  claim 1 , wherein the substrate is not heated via a furnace during the deposition of the mullite in a manner that substantially raises the substantially uniform temperature of the substrate in conjunction with the deposition of the mullite. 
     
     
         12 . The method of  claim 1 , wherein thermal spraying comprises plasma spraying. 
     
     
         13 . The method of  claim 1 , further comprising depositing silicon on the substrate to form a silicon layer before depositing the mullite on the substrate, wherein the silicon layer thickness is approximately 0.5 mils to approximately 5 mils. 
     
     
         14 . A method of coating a substrate, the method comprising:
 depositing silicon on the substrate to form a silicon layer;   heat treating the silicon layer; and   depositing mullite on the silicon layer via thermal spraying to form a first layer subsequent to the heat treatment of the silicon layer, the mullite comprising mullite powder formed via at least one of a fused plus crush or sinter plus crush process.   
     
     
         15 . The method of  claim 14 , wherein the mullite is deposited on the silicon layer during a first time period and the substrate is at a temperature less than approximately 50 degrees Celsius at approximately a beginning of the first time period. 
     
     
         16 . The method of  claim 14 , wherein the heat treatment comprises heat treating the silicon layer at a temperature of about 800 degrees Celsius to about 1250 degrees Celsius for about 0.2 hours to about 4 hours. 
     
     
         17 . The method of  claim 14 , further comprising depositing a second material on the first layer to form a second layer, the second layer comprising at least one of at least one of barium strontium aluminum silicate (BSAS) or a rare-earth silicate. 
     
     
         18 . The method of  claim 14 , further comprising:
 depositing a second material on the first layer to form an intermediate layer; and   depositing a third material on the intermediate layer to form a third layer.   
     
     
         19 . The method of  claim 18 , wherein the intermediate layer comprises approximately 20 to approximately 50 weight percent mullite and at least one of ytterbium di-silicate and ytterbium mono-silicate, and the third layer comprises one of ytterbium di-silicate and ytterbium mono-silicate. 
     
     
         20 . The method of  claim 18 , wherein the intermediate layer comprises ytterbium di-silicate and the third layer comprises ytterbium mono-silicate.