Abradable layer including a low thermal conductivity composition

Abstract

A system may include a blade track or blade shroud and a gas turbine blade that includes a blade tip. The blade track or blade shroud may include a substrate and an abradable layer formed over the substrate. The abradable layer may include at least one of zirconia or hafnia; ytterbia; samaria; and at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia. The abradable layer may include a porosity between about 25 vol. % and about 50 vol. %. The blade track or blade shroud and the gas turbine blade may be configured so the blade tip contacts a portion of the abradable layer during rotation of the gas turbine blade, and the abradable layer may be configured to be abraded by the contact by the blade tip.

1 . A system comprising:
 a blade track or blade shroud comprising:
 a substrate, and 
 an abradable layer formed over the substrate, wherein the abradable layer comprises:
 at least one of zirconia or hafnia, 
 ytterbia, 
 samaria, and 
 at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia, wherein the abradable layer comprises a porosity between about 25 vol. % and about 50 vol. %; and 
 
   a gas turbine blade comprising a blade tip, wherein the blade track or blade shroud and the gas turbine blade are configured so the blade tip contacts a portion of the abradable layer during rotation of the gas turbine blade, and wherein the abradable layer is configured to be abraded by the contact by the blade tip.   
     
     
         2 . The system of  claim 1 , wherein the abradable layer is essentially free from yttria. 
     
     
         3 . The system of  claim 1 , wherein the abradable layer comprises between about 2 mol. % and about 40 mol. % ytterbia, between about 0.5 mol. % and about 20 mol. % samaria, and between about 0.5 mol. % and about 20 mol. % of the at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia. 
     
     
         4 . The system of  claim 3 , wherein the abradable layer comprises at least one of a compound phase, a cubic crystalline phase, or a tetragonal-prime crystalline phase. 
     
     
         5 - 6 . (canceled) 
     
     
         7 . The system of  claim 1 , wherein the abradable layer comprises between a porosity between about 35 vol. % and about 45 vol. %. 
     
     
         8 . The system of  claim 1 , wherein the abradable layer consists essentially of at least one of zirconia or hafnia; ytterbia; samaria; and at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia. 
     
     
         9 . The system of  claim 1 , wherein the abradable layer comprises a greater amount of ytterbia than samaria or the at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia. 
     
     
         10 . (canceled) 
     
     
         11 . The system of  claim 1 , further comprising an environmental barrier layer formed over the substrate, wherein the abradable layer is formed over the environmental barrier layer, and wherein the environmental barrier layer comprises at least one of mullite, barium strontium aluminosilicate, calcium aluminosilicate, cordierite, lithium aluminosilicate, or a rare earth silicate. 
     
     
         12 . (canceled) 
     
     
         13 . The system of  claim 1 , further comprising a CMAS-resistant layer formed over the substrate, wherein the CMAS-resistant layer comprises alumina and at least one rare earth oxide. 
     
     
         14 . The system of  claim 13 , wherein the CMAS-resistant layer further comprises at least one of silica, TiO 2 , Ta 2 O 5 , HfSiO 4 , an alkali oxide, or an alkali earth oxide. 
     
     
         15 - 16 . (canceled) 
     
     
         17 . The system of  claim 1 , wherein the abradable layer comprises a first abradable layer, further comprising a second abradable layer formed over the substrate, wherein the second abradable layer comprises a rare earth silicate and at least one of alumina, TiO 2 , Ta 2 O 5 , HfSiO 4 , an alkali oxide, or an alkali earth oxide. 
     
     
         18 - 19 . (canceled) 
     
     
         20 . The system of any of  claims 1  to  19 , wherein the substrate includes a plurality of features formed in the substrate, and wherein the plurality of features comprise at least one of grooves, ridges, circular depressions, circular protrusions, hexagonal depressions, hexagonal protrusions, elliptical depressions, or elliptical protrusions. 
     
     
         21 . (canceled) 
     
     
         22 . The system of any of  claims 1  to  19 , further comprising a feature layer formed on the substrate, wherein the feature layer includes a plurality of features formed in the feature layer, and wherein the plurality of features comprise at least one of grooves, ridges, circular depressions, circular protrusions, hexagonal depressions, hexagonal protrusions, elliptical depressions, or elliptical protrusions. 
     
     
         23 . (canceled) 
     
     
         24 . A method comprising:
 forming an abradable layer over a substrate of a blade track or a blade shroud using a thermal spraying technique, wherein the abradable layer comprises:
 at least one of zirconia or hafnia, 
 ytterbia, 
 samaria, and 
 at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia, wherein the abradable layer comprises a porosity between about 25 vol. % and about 50 vol. %; 
   configuring a blade tip of a gas turbine blade relative to the blade track or blade shroud so the blade tip contacts a portion of the abradable layer during rotation of the gas turbine blade; and   rotating the gas turbine blade to cause the blade tip to contact and abrade the portion of the abradable layer.   
     
     
         25 . The method of  claim 24 , wherein forming the abradable layer over the substrate comprises forming the abradable layer over the substrate using plasma spraying. 
     
     
         26 . The method of  claim 24 , wherein forming the abradable layer over the substrate comprises:
 depositing a coating material additive and coating material over the substrate using a thermal spraying technique, wherein the coating material comprises the at least one of zirconia or hafnia; ytterbia; samaria; and the at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia, and wherein the coating material additive comprises at least one of graphite, hexagonal boron nitride, or a polyester; and   after depositing the coating material additive and coating material over the substrate using the thermal spraying technique, heat treating the coating material additive and the coating material to remove the coating material additive and form pores in the abradable layer.   
     
     
         27 - 28 . (canceled) 
     
     
         29 . The method of  claim 24 , further comprising forming an environmental barrier layer over the substrate, wherein forming the abradable layer over the substrate using the thermal spraying technique comprises forming the abradable layer over the environmental barrier layer using the thermal spraying technique. 
     
     
         30 . The method of  claim 24 , further comprising forming a CMAS-resistant layer over the substrate, wherein forming the abradable layer over the substrate using the thermal spraying technique comprises forming the abradable layer over the CMAS-resistant layer using the thermal spraying technique. 
     
     
         31 . (canceled) 
     
     
         32 . The method of  claim 24 , further comprising forming features in the substrate. 
     
     
         33 . The method of  claim 24 , further comprising forming a feature layer over the substrate and forming features in the feature layer, wherein forming the abradable layer over the substrate using the thermal spraying technique comprises forming the abradable layer over the feature layer using the thermal spraying technique.