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An ablation resistant coating with self-transpiration cooling effect was prepared on the surface of aluminum alloy by dilution effect of high speed laser cladding. The coatings mainly contain ablation resistant phases ZrB 2 and SiC, and low-melting phases Al and Al 3.21 Si 0.47. The ablation property of coatings was investigated at different heat fluxes (35.39, 70.77, 106.16, 141.54) MW⸱m−2. The mass ablation rate increased gradually, and the morphology of ablation region changed significantly with the increased heat flux. The self-transpiration cooling effect of coatings was studied by phase, morphology, and element distribution of ablation region. The self-transpiration cooling effect weakened the oxidation behavior of ZrB 2 and SiC at heat fluxes of 35.39 and 70.77 MW⸱m−2 and protected the coating from being exhausted when the heat fluxes were 106.16 and 141.54 MW⸱m−2. [ABSTRACT FROM AUTHOR]

Herein, the effects of Gd2O3 on the laser cladding NiCoCrAlYTa coatings in terms of microstructure, phase structures, high temperature oxidation behaviors were investigated. The results showed that the addition of Gd2O3 changed the composition of coating phases, promoted homogeneous phase distribution, reduced porosity and improved coating density. During oxidation at 1100 °C for 150 h, the increase in the content of added Gd2O3 (at mass fractions of 0, 0.5, 1, 2, 5 and 10%) exhibited an initial inhibitory and then increased effect on the weight-gain rate of the coatings. Overall, 1% Gd2O3 addition resulted in the greatest improvement in the oxidation resistance of the coatings, with 49.58% decreases in oxidation kinetic constants, respectively, compared with those of unmodified coatings. However, at a Gd2O3 content of 10%, the thermally grown oxide on the coating surface exhibited large flaking areas. The high-temperature oxidation kinetic parameters of the coatings exhibited an inverted parabolic form with increasing Gd2O3 content. The higher Gd2O3 content led to the formation of excessive oxygen diffusion channels along grain boundaries, which is the reason for the decrease in the anti-oxidant performance of the coating. [ABSTRACT FROM AUTHOR]

In this work, rare-earth elements Eu and Y were added to La2Zr2O7 (LZ) as doping elements, and the ceramic coating of (La0.5Eu0.25Y0.25)2Zr2O7 (LEYZ) was prepared. The evolution of the sintering resistance, thermal shock resistance, and thermal insulation properties of the multi-element rare-earth co-doped modified coatings under long-term and high-temperature conditions was studied. The results showed that the sintering resistance of the doped coating was significantly improved, and the coating still does not fall off after 200 h at 1100 °C. The thermal shock life of the coating at 1000 °C is increased by 47% compared with that of the undoped modified LZ coating. The length of the vertical cracks in LEYZ ceramic layer is obviously shorter than that in LZ coating, which will be more beneficial to preventing the coating from peeling off. Compared with LZ coating, the insulation temperature of the LEYZ ceramic coating is increased by 24, 26 and 34% in the range of 900 ~ 1100 °C, respectively. The coating has the best thermal insulation effect, which is consistent with theoretical calculation results. The results demonstrate that the modified lanthanum zirconate coatings doped with Europium and Yttrium has great potential in high-temperature performance. [ABSTRACT FROM AUTHOR]

The (La0.5Eu0.25Y0.25)2Zr2O7 (LEYZ) ceramic powder for spraying was prepared and synthesised by combining spray granulation and solid phase reaction phase, and a double ceramic layer structure with (La0.5Eu0.25Y0.25)2Zr2O7 ceramic surface coating and YSZ intermediate coating was prepared by atmospheric plasma spraying. Experimental characterisation revealed that the moulding state of spray granulated powders was significantly influenced by the solid content. When the solid content is small, the viscosity of the slurry is insufficient, and the prepared powder has poor formability and small overall particle size. When the solid content is large, the slurry is too viscous, which easily leads to unfavourable conditions such as sticky walls. The best formability of the pelletised powder was obtained with a solid content of 55 wt-% and a binder content of 2.0 wt-%. Compared with La2Zr2O7 (LZ) ceramics, the fracture toughness of the rare-earth co-doped modified LEYZ ceramic coating was increased by 8.4% and the bond strength was increased by 49.9%, showing good toughness and crack resistance. Moreover, LEYZ coating has significantly better resistance to solid phase particle erosion than LZ coating, with 46.3% and 45.4% reduction in erosion rate at 45° and 90°, respectively. [ABSTRACT FROM AUTHOR]