Research On Depositing Characteristic And Performance Of The Metal/Ceramic Thermal Barrier Coating By Cold Spraying

With the rapid development of aviation and navigation, the demands for the materials with high performance for gas turbine and the internal combustion engine are increasing. Due to the high temperature-and corrosion-resistance, the thermal barrier coatings (TBCs) are extensively used for the protection of aircraft blades and industrial gas turbines.In the cold gas dynamic spraying (CGDS) process, solid particles are accelerated in a supersonic inert gas flow and directed towards the object to be coated. The main coating characteristics are:low porosity level; absence of oxidation; good adherence to the substrate; high microhardness; absence of chemical reaction and microstructural changes. The cold spraying technology, which makes up the deficiencies of the tradition thermal spraying, improves the performances of the TBCs.In this paper, the characters of the NiCoCrAlY/ZrO2 coating were studied through XRD, SEM, micro-hardness test, combination test, thermal shock resistance test and anticorrosion experiment. In order to discuss the relationship between the abrasion, defection and the properties of the coating, the performances of the defected NiCoCrAlY/ZrO2 coatings were also investigated.The results showed:little or no microstructural changes occurred in the CGDS deposition process; as-deposited coatings presented the dense microstructure, high hardness and high tensile strength (the NiCoCrAlY/ZrO2 coating:HV 400-600, 40.4 Mpa; the NiCoCrAlY coating:HV 400-500,37.5 Mpa). The performances of the as-deposited coatings were good, but not better than those of the coatings which were deposited when He was as process gas (porosity level:about 1.2%, microhardness:HV 600-800). At the beginning of anodic polarization, the coatings reflected a passive trend, which implied the formation of a passive film. After about 1 day's immersion in seawater, it was evident that no clear passive trend behavior was presented in NiCoCrAlY coating, while the NiCoCrAlY/ZrO2 coating still exhibited a passive trend. The lower corrosion current and the higher polarized resistance proved the excellent anticorrosion performance.The EIS spectrums were consisted of one semicircle, whose radius enlarged continuously before stabilization. For the CoNiCrAlY/ZrO2 coating, the time constants increased to two after 38 day's immersion, and then to three after 103 day's immersion. There were no productions of iron corrosion from beginning to end.The thermal shock resistance tests showed that cracks appeared after seven times tests for the CoNiCrAlY/ZrO2 coating, while four times tests for the CoNiCrAlY coating. Besides, the cracks on the CoNiCrAlY coating were finer than that on CoNiCrAlY/ZrO2 coating.After about 1 day's immersion, the EIS spectrums were consisted of two inconspicuous time constants for the defected NiCoCrAlY/ZrO2 coating. With the immersion time increasing, two time constants appeared distinctly and the corrosion of the substrate was serious.