Ceramic coatings have low thermal conductivity. They provide potential for increased engine performance, reduced fuel consumption, use of less costly materials or construction procedures, and increased life and durability

Liebert, C. H.

Stecura, S.

English

NASA Technical Reports Server

December 1975	 B75-10290 
.
NASA TECH BRIEF. 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be d!rected to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Ceramic Thermal Protective Coating 
Withstands Hostile Environment of Rotating Turbine Blades 
.
A simple, two-layer, highly adherent, ceramic coating 
of an NiCrAIY bond coat and a yttria- (Y 2 03 ) or 
magnesia- (MgO) stabilized zirconia thermal barrier over-
layer has been developed to resist the thermal, erosive and 
corrosive environment and centrifugal stresses 
encountered by gas turbine engine blades. 
The ceramic coatings. have a low thermal conductivity 
and therefore impose a thermal barrier between high 
temperature combustion gases and air-cooled metal parts 
such as combustor and turbine blades and vanes in aircraft 
engines, power generating turbines, or other cooled 
component applications. These low thermal conductivity 
ceramic coatings insulate the working parts thereby 
providing reduced metal temperatures, increased cycle 
temperatures or decreased coolant requirements. These 
features provide a potential for increased engine per-
formance, reduced fuel consumption, use of less costly 
materials or construction procedures and increased life 
and durability. 
This new NiCrAIY/zirconia coating on an air-cooled 
blade completed a severe test consisting of 500 one-
minute cycles in a J-75 gas turbine engine at coating 
surface temperatures of 1338 K(1950°F) with no adverse 
effects. In tests conducted in an engine combustion gas 
simulation facility, the coating withstood 3200 1.2- 
n-dnute  cycles at 1561 K (2350°F) and 1950 cycles at 
1644 K (2500°F) with only very low cooling air flow 
needed to maintain the substrate metal temperatures 
between 1172 and 1244 K (1650 and 1780°F). Test times 
greater than 200 hours with temperature drops across the 
ceramic coating as high as 755 K (900°F) have also been 
achieved.
The NiCrA1Y bond coating is plasma sprayed onto the 
turbine blade to a thickness from 0.0076 cm (0.003 in) to 
0.0177 cm (0.007 in) in an air environment, therefore, no 
special cover gas or inert atmosphere chamber is needed. 
The adherence capability is five times that of previous 
Ni-20Cr alloy bonds. Similarly, the NiCrA1Y bond coat 
has superior adherence to the plasma sprayed zirconia 
barrier coating. The zirconia coating can be polished to 
reduce aerodynamic frictional losses as well as to further 
improve resistance to cracking under operating stresses. 
Note: 
Requests for further information should be directed 
to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B75-10290 
Patent Status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
NASA Patent Counsel 
Mail Stop 500.113 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Source: C.H. Liebert and S. Stecura
Lewis Research Center 
(LEW.12554) 
Category 04 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United Stales 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Ceramic thermal protective coating withstands hostile environment of rotating turbine blades

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