The Preparation And Application Of Silica Based Ceramic Core In The Casting Of Nickel-based Superalloy Hollow Blade

Focus on th e application of nickel-based superalloy single-crystalhollow blade for aircraft engine, silica-based ceramic cores with highmechanical strength and good thermal shock resistance was prepared usingthe hot pressing molding method in this dissertation. The ceramic coreswas proved not to occur chemical reaction with nickel-based superalloyCMSX-6at high temperature1550℃.During the preparation process of ceramic cores, the particle sizedistribution of silica matrix powders was optimized according todifferent-diameter-ball filling model; the effect of temperature andconcentration of surfactant on the ceramic slurry rheological property wasdiscussed. The rheological curves of ceramic slurry at different conditionswere fitted, and the constitutive equation with excellent matching degreewas given. On this basis, according to the optimization of powder gradingmethod and the optimum conditions for ceramic slurry rheologicalproperties, as well as in combination with other researchers’ results, thesilica based ceramic cores were prepared and the mechanical properties,thermal physical properties, hole structures together with the physicalphase and microstructure characterization was analysed. Then the ceramiccores and shells were assembled to cast nickel-based superalloy hollowblade. The matching properties and the adaptability of ceramic cores andshells for nickel-based superalloy hollow blade casting was investigatedsystematically. The main results as follows:(1)For silica-based ceramic cores, high filling compactness andexcellent flexural strength at both high and low temperature can be achieved with silica matrix powders which meetdifferent-diameter-ball filling model. And the silica powdersparticles size distribution was supposed to be a bimodal ormultimodal distribution.(2)Temperature and the concentration of surfactant showed importantinfluence on the rheology properties wax-based ceramic slurry.According to the testing results, the most suitable temperature andsurfactant concentration were respectively120℃and0.4wt%.The wax-based slurry was proved to be non-Newtonian fluid, andmay not meet the same rheological constitutive equation atdifferent temperature and concentration conditions; besides, itshowed shear-thinning behavior.(3)The main phase of ceramic cores sintered at1200℃wasβ-cristobalite, and there still had obvious amorphous silica glassphase. Re-sintered at1550℃for2h, all the amorphous glassphase turned into β-cristobalite phase with the skeleton densityincreasing, the hole-structure more clear, the quantity and length ofthe cracks increasing, and the residual strength reduced which wasgood for core leaching. The linear expansion coefficient ofceramic cores decreased with the temperature increasing to1350℃but rose when the temperature is above1350℃.(4)The results showed4positions-fixing combined with platinumfilament flank supporting method achieved excellent positioningperformance. Besides the nickel-based alloy hollow blade wassuccessfully casted using the ceramic cores manufactured in thisarticle at the temperature of1550℃.