[Effects of recasting in vacuum with argon on the chemical composition of ceramic alloys].

OBJECTIVE: This study aimed to determine the effect of recasting in vacuum with argon on the chemical composition of cobalt-chromium (Co-Cr), commercially pure titanium (cpTi), palladium-based (Pd-based), and aurum-platinum (Au-
Pt) ceramic alloys. METHODS: Without adding new alloys, Co-Cr, cpTi, Pd-based, and Au-Pt ceramic alloys were recast one to three times under the condition of vacuum compressive casting with argon. Before recasting, four previously cast ceramic alloys were treated with the corresponding method. After polishing, the chemical composition of the four ceramic alloys recasted one to three times were determined by energy-dispersive spectrometry. RESULTS: No significant difference was observed in the chemical composition of the four ceramic alloys recast 1-3 times (P>0.05). CONCLUSIONS: Under the condition of vacuum with argon, the recasting had no obvious influence on the chemical composition of Co-Cr, cpTi, Pd-based, and Au-Pt ceramic alloys.

[The effect of recasting on microstructure of dental ceramic alloys].

PURPOSE: To investigate the effects of recasting on metallographic microstructure of cobalt-chromium(Co-Cr), commercially pure titanium(cpTi), palladium-copper-gallium(Pd-Cu-Ga), aurum-platinum(Au-Pt) ceramic alloys. METHODS: Without adding new alloys, Co-Cr, cpTi, Pd-Cu-Ga and Au-Pt ceramic alloys were recasted for 1-3 times under the circumstance of vacuum compressive casting with argon. Before each recasting, these 4 ceramic alloys casted previously were treated by the most appropriate way which has been reported by our previous study. According to GB/T13298-2015 standards, the specimens of 4 ceramic alloys after recasting 1-3 times were grinded, polished, and etched and then the metallographic microstructure of them were determined by a metallographic microscope or scanning electron microscopy(SEM). RESULTS: With the increase of recasting times, the microstructure of Co-Cr ceramic alloy showed grain growth, grain matrix increase, and the intermetallic compound in the grain boundary increase, the microstructure of the cpTi ceramic alloy showed grain growth. The samples of cpTi ceramic alloy recasting twice appeared shaft tendency, and the ones which were recasted 3 times were compound of α-phase and ß-phase. The microstructure of the Pd-Cu-Ga ceramic alloy showed grain growth slightly after casting 2-3 times, while no significant change was found on the microstructure of the Au-Pt ceramic alloy. CONCLUSIONS: Recasting changes the microstructure of Co-Cr, cpTi, and Pd-Cu-Ga ceramic alloys, and the ceramic alloys may recycled by the manufacturers.