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KMID : 1035320150420020095
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Korean Society for Dental Materials
2015 Volume.42 No. 2 p.95 ~ p.106
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Hardening mechanism associated with post-firing heat treatment of softening heat treated and then firing simulated Pd-Ag-Au alloy for bonding porcelain
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Kim Sung-Min
Yu Young-Jun
Cho Mi-Hyang
Kwon Yong-Hoon
Kim Hyung-Il
Seol Hyo-Joung
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Abstract
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Hardening mechanism associated with post-firing heat treatment of softening heat treated and then firing simulated Pd-Ag-Au alloy for bonding porcelain was examined by observing the change in hardness, crystal structure and microstructure. By post-firing heat treatment of as-cast, solution treated and pre-firing heat treated specimens at 650 ℃ after casting, the hardness value increased within 10 minutes. Then, hardness consistently increased until 30 minutes, and gap of hardness value among the specimens was reduced. The increase in hardness after post-firing heat treatment was caused by grain interior precipitation in the matrix. The softening heat treatment did not affect the increase in hardness by post-firing heat treatment. The precipitated phase from the parent Pd-Ag-Au-rich α phase with face-centered cubic structure by post-firing heat treatment was Pd3(Sn, In) phase with face-centered tetragonal structure, which has lattice parameters of a200=4.0907 Å, c002=3.745 Å. From above results, appropriate post-firing heat treatment in order to support the hardness of Pd-Ag-Au metal substructure was expected to bring positive effects to durability of the prosthesis.
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KEYWORD
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Pd-Ag-Au alloy, Post-firing heat treatment, Simulated complete firing, Grain interior precipitates, Hardening
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