0.9% NaCl 용액에서 치과용 주조합금의 공식거동
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- The important factor to decrease the failure of partial denture is the minimization of casting defects at minor connector and clasp. The defects of partial denture frame works are mainly shrinkage porosity, inclusions, micro-crack, particles from investment, and dendritic structure.
Three casting alloys(PDS: 63Co-27Cr-5.5Mo, Ticonium: 63Ni-16Cr-5Mo, Wironit: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; CF:centrifugal casting(Kerr,USA), HFI:high frequency induction casting(Jelenko Eagle,USA), VP:vacuum pressure casting(Bego,Germany). The casting temperature was 1380℃ (A and B) and 1420℃ (C). The corrosion and casting morphologies were analyzed using SEM, EDX, and OM. The pitting corrosion of the samples was examined through potentiodynamic polarization test, cyclic potentiodynamic polarization test, potentiostatic test method in 0.9% NaCl solutions at 36.5±1℃.
These results are as follows:
1. Dendritic structure showed in the case of PDS and Wironit alloy, and columnar structure appeared in Ticonium alloy. In the PDS and Wironit alloy, α-Co and ε-Co were appeared at matrix and γ'-Ni2Cr second phase showed in Ticonium alloy.
2. Pitting potentials of PDS and Wironit were higher than Ticonium from potentiodynamic test.
3. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.
4. Corrosion resistances of PDS and Wironit were superior to that of Ticonium from potentiostatic test at 300mV.
It was concluded that the pitting potential, pit nucleation time and surface stability with casting methods increased in the order of vacuum pressure casting, high frequency induction casting and centrifugal casting method from electrochemical test.
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