The mechanism and influence of re-dissolution in zirconium diacetate-yttria shell for titanium investment casting

Abstract:

The re-dissolution of zirconium diacetate- yttria shell (ZA-Y shell) and its impact were studied. The re-dissolution rate under hot water and steamin miosture condition was measured by the balance. Three-point flexural strength was measured using the universal testing machine, and the fracture index was calculated. The distribution of the surface precipitates was observed by Ooptical microscope was used to observe the distribution of the surface precipitates, and its morphology and composition were tested using scanning electron microscopy (SEM) combined with energy spectrum analysis (EDS). Composition of the ZA-Y shell was measured by X-ray fluorescence (XRF) method. The reason of the precipitates was analysed. The results suggest the re-dissolution is limited. The maximum water penetration rate is 2.5% and the dissolution rate is 0.8% in 20 min. The strength reduces 26% and fracture index reduces to 66%. The surface precipitates are due to dissolution of ammonium metatungstate (AMT) and own two reasons: drastictoo high pressure release or fast drying condition with slow heat dissipation.