COBEM99

S18 Processos Mecânico-Metalúrgicos

Title:

MECHANICAL CHARACTERIZATION OF POST TREATED THERMAL BARRIER COATINGS USING FOUR POINT BENDING

Summary :

THERMAL BARRIER COATINGS OR TBCS HAVE BEEN WIDELY USED, MAINLY ON GAS TURBINE AND DIESEL ENGINES. THE MOST COMMON MATERIAL USED AS AN INSULATOR IN SUCH SYSTEMS HAS BEEN PARTIALLY STABILIZED ZIRCONIA (PSZ) NORMALLY OVERLAID ONTO A METALLIC BOND COAT LAYER BY PLASMA SPRAYING. THE OBTAINED CERAMIC LAYER IS NORMALLY POROUS, IMPROVING THE INSULATING PROPERTIES. HOWEVER, THAT POROSITY ALSO INCREASES GAS PERMEABILITY AND THEREFORE REDUCES THE OXIDATION RESISTANCE OF THE COATING. POST-TREATMENTS HAVE BEEN APPLIED IN ORDER TO REDUCE GAS PERMEABILITY, MAINLY USING SOL-GEL TECHNOLOGY. IN GENERAL, MECHANICAL PROPERTIES OF POST-TREATED COATINGS ARE NOT ADDRESSED IN SUCH STUDIES. IN THIS WORK THERMAL BARRIER COATINGS (TBCS) WERE APPLIED ON LOW CARBON STEEL SUBSTRATES, USING TWO DIFFERENT SETS OF BOND COAT, I.E., METALLIC AND METAL-CERAMIC. SOL-GEL WAS USED TO POST-TREAT THE COATINGS IN ORDER TO IMPREGNATE THE POROUS CERAMIC TOPCOAT WITH ALUMINA OR ZIRCONIA. THE SAMPLES IN THE AS SPRAYED AND POST-TREATED FORM WERE CHARACTERIZED USING FOUR POINT BEND TESTS. ACOUSTIC EMISSION WAS USED TO IN SITU MONITORING CRACKING DEVELOPMENT UNDER FOUR POINT BENDING. THE ACOUSTIC EMISSION RESULTS ARE PRESENTED BASED IN ENERGY DISTRIBUTIONS, WHICH ARE LINKED TO CRACK BEHAVIOR DURING THE TEST. KEY WORDS: PLASMA SPRAY, SOL-GEL, COATING, CERAMIC, METAL

Author :

Berndt, Christopher C.
Lima, Rogerio Soares
Lima, Carlos Roberto Camello
Senturk, Ufuk 0

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