Study On Interface Reaction Between Zirconium Melts And Oxide Type Casting Shell

With the application of zirconium and zirconium alloy is more and more widely in aerospace,nuclear and chemical industry, zirconium alloy often need to be processed into a variety of complexshape parts, adopting the method of mechanical cold working and welding technology formingzirconium products is inefficient, wasteful and poor of overall stability. Therefore, choose revestmentprecision casting technology processing complex structure zirconium base components showed abroad application prospect. And due to the high chemical activity, zirconium melts is easy to reactwith the shell mold and reduce the dimensional accuracy and surface quality of casting. So studyingthe interface reaction between the zirconium and shell mold and choosing the stabil shell moldmaterials and appropriate preparation process is the key of the zirconium investment castingtechnology.This article selects Al2O3, ZrO2(stable by CaO), ZrO2(stable by Y2O3), Y2O3to react withzirconium melts which are used to be Shell material for the revestment precision casting of Lively andhigh melting point metal. The interface reaction between Al2O3, ZrO2(stable by CaO), ZrO2(stable byY2O3), Y2O3and Zirconium melts was studied by scanning electron microscopy (SEM), energydispersive spectroscopy(EDS), X-Ray Diffraction(XRD), etc. The results indicate that Four kinds ofoxide shell material reacted with Zirconium melts. zirconium sample surface was contaminated byoxide and form the hard contamination layer. The contamination layer contains the O in Zr solidsolution and Zirconium oxide. The surface structure of the zirconium reacting with Al2O3and ZrO2（stable by CaO） is osteoporosis and form a large number of cold cracks and pores, and thethickness of their contamination layer is100μm and35μm; The surface structure of the zirconiumreacting with ZrO2（stable by Y2O3）and Y2O3is more dense and the thickness of their contaminationlayer is30μm and25μm.On the basis of the above test and analysis, The mechanism of interface reaction between Al2O3,ZrO2(stable by CaO), ZrO2(stable by Y2O3), Y2O3and zirconium melts was studied by Differentialthermal analysis(DTA) and Midema generated heat model. The results indicate that The Al of Al2O3can reduce the activity of zirconium melts, but the stability of Al2O3is poorer and substitutionreaction happened severe; Zr decomposd out of ZrO2(stable by CaO) and ZrO2(stable by Y2O3) anddissolved into zirconium melts, which Promoted the interface reaction. The Ca and Y of ZrO2(stableby CaO) and ZrO2(stable by Y2O3) can improve the activity of zirconium melts, but the ability of Y isweaker than Ca, and the content of Y is less than Ca in zirconium melts. Thus the interface reactionbetween ZrO2(stable by CaO) and zirconium melt is more severe than ZrO2(stable by Y2O3). The Y element of Y2O3improved the activity of zirconium melts, but the free energy of Y2O3is higher, thereis less decomposition in zirconium melts, least interface reaction.Make the ZrO2(stable by Y2O3) into casting shell and pour zirconium liquid which has highstability and practical industrial application significance. Study the the morphology of shell structureand surface reaction layer structure of zirconium castings by scanning electron microscopy (SEM),energy dispersive spectroscopy(EDS), X-Ray Diffraction(XRD) test, etc. The results indicate thatparticle size distribution and powder liquid ratio of ZrO2(stable by Y2O3) have important influence oninterface reaction. When the particle size distribution adjust from5Wt%(The mass fraction of Finepowder) to30Wt%, The thickness of surface contamination layer of casting decrease gradually from50μm to15μm. The size and quantity of surface cold crack is reduced, the degree of interfacialreaction tend to be more weak. The thickness of surface contamination layer decreased with powderliquid ratio increasing. When powder liquid ratio increased from4.0g/ml to5.5g/ml, The thickness ofsurface contamination layer decreased from25μm to15μm around. And casting surface structure ismore compact, the quantity of pore and cold crack was reduced, interface reaction degree was reduced.The main reason is that adjusting particle size distribution and powder liquid ratio improved theparticle density of casting shell and reduced the surface roughness, thereby reduced contact areabetween solid and liquid and the interface wettability, improved the contact state between zirconiummelts and ZrO2(stable by Y2O3) shell.