HIGH TEMPERATURE, PROTECTIVE COATINGS ARE CURRENTLY APPLIED BY SEVERAL PROCESSES INCLUDING ELECTRON BEAM EVAPORATION, PACK CEMENTATION, CHEMICAL VAPOR DEPOSITION, SPUTTERING, AND PLASMA SPRAYING.

HIGH TEMPERATURE, PROTECTIVE COATINGS ARE CURRENTLY APPLIED BY SEVERAL PROCESSES INCLUDING ELECTRON BEAM EVAPORATION, PACK CEMENTATION, CHEMICAL VAPOR DEPOSITION, SPUTTERING, AND PLASMA SPRAYING. LASER CLADDING IS A FAIRLY NEW PROCESS THAT OFFERS THE UNIQUE ADVANTAGES OF CONTROLLED DILUTION, GOOD FUSION BOND, FINE MICROSTRUCTURES, MINIMAL DAMAGE TO THE SUBSTRATE, DEPOSITION OF HIGH MELTING POINT MATERIALS, COATING OF INACCESSIBLE AND LOCALIZED AREAS, AND DEFECTFREE HOMOGENEOUS STRUCTURES. IN THE PROPOSED INVESTIGATION, TWO CONTINUOUS-WAVE CO(2) GAS LASERS WITH POWER LEVELS 5 KW (MULTI MODE BEAM) AND 1.2 KW (GAUSSIAN BEAM) WILL BE EMPLOYED TO CLAD THERMAL BARRIER COATINGS USING A MELT/PARTICLE INJECTION PROCESS. THE COATING SEQUENCE INVOLVES A BOND-COAT OF NICRALY, FOLLOWED BY AN INTERMEDIATE COAT OF AL(2)O(3) AND AN OVERCOAT OF ZROO(2)/Y(2)O(3). THE PURPOSE OF INTERMEDIATE AL(2)O(3) COATING IS TO PREVENT THE OXIDATION OF BOND-COAT DURING ITS HIGH TEMPERATURE USE AND TO ENHANCE THERMALBARRIER CHARACTERISTICS. CYCLIC OXIDATION TESTS AT 2000 DEG F WILL BE CONDUCTED TO EVALUATE THE HIGH-TEMPERATURE PREFORMANCE OF CLADDINGS. LIGHT MICROSCOPY, SCANNING ELECTRON MICROSCOPY, MICROPROBE ANALYSIS, AND HARDNESS TESTS WILL BE USED TO CHARACTERIZE THE COATINGS BEFORE AND AFTER HIGH-TEMPERATURE ENVIRONMENTAL EXPOSURE. THE OBJECTIVE OF PHASE I PROGRAM IS TO DETERMINE THE FEASIBILITY OF LASER CLADDING PROCESS FOR OBTAINING DEFECT-FREE, DENSE, UNIFORM, COHERENT, THICK AND HIGH-DEPOSITION RATE CLADDINGS.