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KMID : 1035320160430030273
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Korean Society for Dental Materials
2016 Volume.43 No. 3 p.273 ~ p.280
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Effects of Cooling Rate on Hardness Change of a Pd-Au-Ag-Sn Metal-Ceramic Alloy During Porcelain Firing Simulation
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Kim Min-Jung
Shin Hye-Jung
Kwon Yong-Hoon
Kim Hyung-Il
Seol Hyo-Joung
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Abstract
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Effects of cooling rate on change in hardness of a Pd-Au-Ag-Sn metal-ceramic alloy during porcelain firing simulation were examined by observing the change in hardness, crystal structure, and microstructure. Precipitation in the grain and grain boundaries which occurred during cooling after porcelain firing process resulted in hardening of the alloy. The most effective cooling rate for hardening of the alloy was stage 3, which was relatively slow cooling rate. By cooling at different cooling rates after the first firing process, oxidation, the hardness of alloy became apparently different. By further firing simulation, the hardness of alloy decreased constantly at each cooling rate. Such a softening during porcelain firing process resulted from the microstructural coarsening of the precipitates which formed in the grain interior and boundaries.
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KEYWORD
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Pd-Au-Ag-Sn alloy, Firing simulation, Precipitation harding, Cooling rate
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