Laser scanning modification was applied to secondarily melt the top ceramic coating surface of lanthanum zirconate/yttria-stabilized zirconia double ceramic thermal barrier coatings (LZO/YSZ TBCs) to reduce the gas oxygen diffusion and improve the TBCs service life. Isothermal oxidations with different times were carried out on the as-sprayed (AS) TBCs and laser-remolten (LR) TBCs at 1100 °C to investigate thermally growth oxide (TGO)growth mechanisms and isothermal oxidation behaviors. The results showed that the laser-remolten top-ceramic-coating dense layer with a columnar crystal structure of LR TBCs presented a 96.3% and 59.1% lower surface roughness and porosity, respectively, than those of the top ceramic coating of AS TBCs, and the TGO growth rate of LR TBCs decreased by 46.2% compared to that of AS TBCs. The mixed-oxides appearance time of LR TBCs (50 h) was later than that of AS TBCs (25 h). After 100 h of isothermal oxidation, the total TGO thickness of LR TBCs was only 77.2% of that of AS TBCs, and the effects of the laser-remolten TBCs on gas oxygen diffusion inhibition and high-temperature oxidation resistance were promising in LZO/YSZ TBCs.
Four composite coatings of aluminum, zinc, aluminum zinc and high aluminum bronze were prepared by low-pressure cold spraying technology on 45 steel substrate. Study on microstructure and corrosion resistance of coating by scanning electron microscopy, electrochemical workstation and static immersion. The results showed that compared with the other three coatings. The high aluminum bronze coating was the lowest porosity(0.41%), the highest self-corrosion potential (-1.38v), and the lowest corrosion rate (0.044mm/a), The coating shows good corrosion resistance and can provide long-term and effective protection for the substrate.
Different volume ratios of Al2O3 powder and copper powder are mixed, and a copper-based composite coating is prepared on a pure copper matrix by low-pressure cold spraying technology.The hardness and bond strength of the coating were tested, and the cross-section of the coating was observed and analyzed with a field emission scanning electron microscope. The effect of Al2O3 content in the original powder on the coating performance was investigated.The experimental results show that the copper-based composite coating prepared from copper powder with a particle size range of 10-40μm has a lower porosity and a denser coating structure.With the increase of the content of Al2O3 in the original powder, both the microhardness and the bond strength of the coating showed a law of increasing first and then decreasing. When the content of Al2O3 was 20%, the coating had the best performance.
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