| Nanomaterials are widely paid more attention in various fields including coating technology owing to its unique performances. However, nanocrystalline powder purchased from market can not be directly used as thermal spray feedstock, because of its low density,low fluidity and low mass of individual nanocrystalline particle, it must be reconstituted into nano-particles agglomerates for plasma spraying. In this paper, Al2O3-TiO2-ZrO2 feedstock were fabricated by spray-drying combined with heat treatment sintering, and then the plasma spray technique was used to deposit coating with them. The microstructure and phase composition of the feedstocks and as-sprayed coatings were characterized with XRD and SEM. Mechanical properties of coatings such as: microhardness,fracture toughness, and Wear abrasive resistance were tested. Comparation between self-made and conventional coatings was done in respect of microstructure and mechanical properties. The main results obtained are described as follows:(1) Sprayable feedstock with submicron Al2O3 ,TiO2 and nano-scale ZrO2 can be fabricated by spray-drying and sintering treatment. The optimized parameters of spray-drying process are solids content 40wt%, binder content 2.0wt%, dispersant content 0.5 wt%, spray-drying temperature 250℃, sintering temperature 1150℃. The powder has well sphericity and better flowability.(2) In the Al2O3-TiO2- ZrO2 coatings, phase take the modification ofα-Al2O3,γ-Al2O3, R-TiO2, t-ZrO2 .(3) The Al2O3-TiO2- ZrO2 coatings exhibit the microstructure of lamellae, which similar to the conventional coating and unmelted homogeneous nano particles dispersively distributed in it.(4) Comparing with the conventional coating, the mechanical properties of the Al2O3-TiO2- ZrO2 coating are greatly higher than those of the conventional coating. The microhardness of the Al2O3-TiO2- ZrO2 coating is 1512.6HV, fracture toughness is 7.49J.cm-2, so the deformability were put up under dry wear test, which bring out superior wear resistance. |
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