Preparation And Study Of ZrO₂ Coatings Deposited By Solution-precuror Plasma Spray

Homogeneous and well-crystallized nano- ZrO₂(Y₂O₃)coatings were made by Solution precursor plasma spray(SPPS)using ZrOCl₂ andY(NO₃)₃ as raw materials, H₂O₂ as a complex compound and NH40H as a precipitant to prepare Solution precursor.The structures and properties of colloids and coatings were characterized by XRD,SEM,EDS,TG-DSC,VIDAS imagine analyzer,71model micro-hardness, granularity analyzed etc.ZrOCl₂·8H₂O and Y(NO₃)₃ were solved in water with H₂O₂ as a complex compound and NH40H as a precipitant.The differences of precipitation pH value for Zr4+ and Y3+ could be reduced after adding hydrogen peroxide because of the complex formed.which imprves the uniformity of component distribution of Y₂O₃ and ZrO₂.parts of cll-can be chenge to cl by Hydrogen Peroxide,it is good for the Cl^-Removing in the latter Test.less than 6 when the PH at the end of the reaction the precursor is Sol but moer than 6 it is Precipitation.Experimental proofs that bethe reactiong end PH between 4 and 8,and The optimum mol ratio of H₂O₂ and Zr⁴⁺was 1:1 ware ander the better condition.The sol heat-weight process had losing-weight process and no losing-weight process.The colloid losing adsorption water,ocombine water,structure water,surfactant evaporation and NH4C1 decomposing processes belonged to losing-weight process.However,metastable tetragonal transformation belonged to no losing-weight process,when make the olution precursor mixed Alcohol in some ratio in the water as the Solvent and the Alcohol is good for reducing the Energy of the plasma arc at the process of SPPS,Thus ensuring the solid particles having a full range of physical and chemical reactions and improve the the crystal structure and performance of the coating.The results shows that there are no layer structure,which are always present in the conventional APS coatings,but the round hole with the consistent size is uniformly distributed in the matrix of the coating.Crystal structure is changed with the concentration of precursor solution,too thin or too thick will does bad effect to the coating.The results shows that 0.8mol/L is better for the coatings.The ZrO₂ coatings showed a mean grain size within nanometer that is smaller than conventional coating grain size.Spray distance and atomization air pressure had important effects on microstructures and properties of coatings.The experiments indicated that nanostructured coatings had preferable microstructures and properties when spray distance was controlled between 80mm and 90mm,atomization air pressure 0.5MPa under other process parameters at certain values.If the amount of Y203 was adulterated differently in ZrO₂ coatings.With spray distance increasing,the porocity of coatings reduced at first,then increased.The micro-hardness had relation with the porocity,the larger porocity being,the smaller micro-hardness.Since Ni/Al bond coatings between coatings and substrates could relax heat stress,the existence of them enhanced thermal cycling performance of coatings.At the same time,the larger porocity,the smaller bore,the evener porocity and the more tetragonal pHase amounts of coatings were,the more excellent thermal cycling performance was.