Durable thermal barrier coating having low thermal conductivity

Abstract

This invention provides a thermal barrier ceramic coating for application to a metallic article, with the ceramic coating having a formula of Re x Zr 1-x O y with Z dissolved in wherein Re is a rare earth element selected from the group consisting of Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Lu, where 0<x<0.5 and 1.75<y<2 and wherein Z is an oxide of a metal selected from the group consisting of Y, Mg, Ca, Hf and mixtures thereof. A preferred embodiment is wherein Re is Nd and Z is yttrium oxide.

1 . A metallic article comprising a metallic substrate and a thermal barrier ceramic coating on its surface with the ceramic coating having a formula of Re x Zr 1-x O y  with Z dissolved in where Re is a rare earth element selected from the group consisting of Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Lu, where 0<x<0.5 and 1.75<y<2 and Z is an oxide of a metal selected from the group consisting of Y, Mg, Ca, Hf and mixtures thereof.  
     
     
         2 . Article of  claim 1  further comprising a metallic bond coat between the ceramic coating and the metallic substrate.  
     
     
         3 . Article of  claim 2  wherein the metallic bond coat is a MCrAlY, wherein M is selected from Ni and/or Co.  
     
     
         4 . Article of  claim 2  wherein the metallic bond coat is intermetallic aluminide.  
     
     
         5 . Article of  claim 1  wherein the ceramic coating has a columnar microstructure.  
     
     
         6 . Article of  claim 5  wherein the columnar microstructure is a straight or a saw tooth structure.  
     
     
         7 . Article of  claim 1  wherein the ceramic coating has a layered microstructure.  
     
     
         8 . Article of  claim 1  further comprising a protective ceramic top coat overlaying the ceramic coating.  
     
     
         9 . Article of  claim 8  wherein the protective ceramic top coat is a dense or a wide columnar microstructure.  
     
     
         10 . Article of  claim 8  wherein the protective ceramic top coat is 6 to 8 wt % YSZ.  
     
     
         11 . Article of  claim 1  wherein the ceramic coating has a thermal conductivity of from about 0.78 to 1.02 W/mK from 600° C. to 1100° C.  
     
     
         12 . Article of  claim 1  wherein the ceramic coating has a coefficient of thermal expansion of about 0.67 to 0.95×10 −6 /° C. from room temperature to 1400° C.  
     
     
         13 . Article of  claim 1  wherein the ceramic coating has been applied by EBPVD, air plasma spray or HVOF.  
     
     
         14 . Article of  claim 2  wherein the metallic article is a turbine component.  
     
     
         15 . Article of  claim 14  wherein the turbine component has a metallic substrate of a nickel or cobalt based superalloy.  
     
     
         16 . Article of  claim 1  wherein the ceramic coating has a thickness within the range of about 5 to 500 μm.  
     
     
         17 . Article of  claim 8  wherein the protective ceramic top coat has a thickness of about 5 to 50 μm.  
     
     
         18 . A metallic article comprising a metallic substrate and a thermal barrier ceramic coating on its surface, the ceramic coating having a formula of Nd x Zr 1-x O y  with yttria dissolved in wherein 0<x<0.5 and 1.75<y<2.  
     
     
         19 . Article of  claim 18  wherein the ceramic has a cubic crystal structure.  
     
     
         20 . Article of  claim 18  further comprising a metallic bond coat between the ceramic coating and the metallic substrate.  
     
     
         21 . Article of  claim 20  wherein the metallic bond coat is a MCrAlY, wherein M is selected from Ni and/or Co.  
     
     
         22 . Article of  claim 20  wherein the metallic bond coat is intermetallic aluminide.  
     
     
         23 . Article of  claim 18  wherein the ceramic coating has a columnar microstructure.  
     
     
         24 . Article of  claim 23  wherein the columnar microstructure is a straight or a saw tooth structure.  
     
     
         25 . Article of  claim 18  wherein the ceramic coating has a layered microstructure.  
     
     
         26 . Article of  claim 18  further comprising a protective ceramic top coat overlaying the ceramic coating.  
     
     
         27 . Article of  claim 25  wherein the protective ceramic top coat is a dense or a wide columnar microstructure.  
     
     
         28 . Article of  claim 25  wherein the protective ceramic top coat is 6-8 wt % YSZ having a thickness of about 5 to 50 μm.  
     
     
         29 . Article of  claim 18  wherein the ceramic coating has a thermal conductivity of from about 0.72 to 1.02 W/mK from 600° C. to 1100° C.  
     
     
         30 . Article of  claim 18  wherein the ceramic coating has been applied by EBPVD, air plasma spray or HVOF.  
     
     
         31 . Article of  claim 18  wherein the metallic article is a turbine component.  
     
     
         32 . Article of  claim 31  wherein the turbine component has a metallic substrate of a nickel or cobalt based superalloy.  
     
     
         33 . Article of  claim 18  wherein the ceramic coating has a density of about 4.7 g/cm 3 .  
     
     
         34 . A method for applying a thermal barrier ceramic coating to a metallic article comprising: 
 forming a ceramic having a formula Re x Zr 1-x O y  with Z dissolved where Re is a rare earth element selected from the group consisting of Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Lu, wherein 0<x<0.5 and 1.75<y<2 and wherein Z is an oxide of a metal selected from the group consisting of Y, Mg, Ca, Hf and mixtures thereof, by doping Z and oxides of Re into a zirconia ceramic; and    applying the ceramic as a coating onto the metallic article.    
     
     
         35 . Method of  claim 34  wherein the ceramic is applied by electron beam physical vapor deposition.  
     
     
         36 . Method of  claim 34  wherein 4 to 15 mole % of Nd 2 O 3  and 2 to 14 mole % Y 2 O 3  are doped into ZrO 2 .  
     
     
         37 . Method of  claim 36  wherein the ceramic is applied by electron beam physical vapor deposition.  
     
     
         38 . Method of  claim 37  wherein  10  mole % of Nd 2 O 3  and 2.6 mole % Y 2 O 3  is doped into ZrO 2  forming Nd 0.1 Zr 0.9 O 1.95  with yttria dissolved in.