Department of Dental Materials, Institute of Translational Dental Science and BK21 PLUS Project, School of Dentistry, Pusan National University, Beomeo-Ri, Mulgeum-Eup, Yangsan-Si, Gyeongsangnam-Do, 626-814, South Korea.
Department of Dental Materials, Institute of Translational Dental Science and BK21 PLUS Project, School of Dentistry, Pusan National University, Beomeo-Ri, Mulgeum-Eup, Yangsan-Si, Gyeongsangnam-Do, 626-814, South Korea.
J Mech Behav Biomed Mater. 2020 Jul;107:103728. doi: 10.1016/j.jmbbm.2020.103728. Epub 2020 Mar 31.
This study examined the effect of the cooling rate on the hardness and its effect on the microstructure during porcelain firing simulation of a Pd-Ag-In-Sn-Ga metal-ceramic alloy. In practice, after each firing step for porcelain bonding, the prosthesis is cooled to room temperature before proceeding to the next firing step. The cooling step is known to allow the hardness of the metal substructure to increase. The aim of the study was to determine whether controlling the cooling rate after each porcelain-firing step increases the hardness of the Pd-Ag-based metal-ceramic alloy. The results showed that the hardness of specimens cooled at a higher cooling rate increased after each firing step compared to specimens cooled at a lower cooling rate (p < 0.05). During cooling after the firing simulation the InPd-based phase of tetragonal structure precipitated from the Pd-Ag-rich matrix of the face-centered cubic structure. Hardening by cooling at a higher cooling rate after firing was the result of the coherency strains that formed at the interface of the Pd-Ag-rich matrix and the metastable phase based on the InPd phase. . The reduced hardness obtained in the specimen cooled at a lower cooling rate after firing resulted from the loss of coherency strains as the fine metastable phases based on the InPd phase were transformed into the coarser stable phase with decreased (c/a) of 0.88. This finding revealed that controlling the cooling rate during porcelain firing simulation improves the hardness of the Pd-Ag-In-Sn-Ga metal-ceramic alloy without an additional heat treatment of the alloy.
本研究考察了冷却速率对钯银铟锡镓金属陶瓷合金烤瓷烧制模拟过程中硬度的影响及其对微观结构的影响。在实际操作中，每次烤瓷结合烧制后，在进行下一次烧制之前，将修复体冷却至室温。众所周知，冷却步骤可以使金属底层的硬度增加。本研究的目的是确定控制每次烤瓷烧制后冷却速率是否会增加钯银基金属陶瓷合金的硬度。结果表明，与冷却速率较低的试样相比，冷却速率较高的试样在每次烧制后硬度增加（p < 0.05）。在烧制模拟后的冷却过程中，四方结构的 InPd 基相从面心立方结构的富 Pd-Ag 基体中析出。烧制后以较高冷却速率冷却导致的硬化是由于 Pd-Ag 富基体和基于 InPd 相的亚稳相界面形成的相干应变所致。烧制后以较低冷却速率冷却的试样硬度降低，是因为基于 InPd 相的细小亚稳相转变为较粗的稳定相，（c/a）降低至 0.88，导致相干应变丧失。这一发现表明，控制烤瓷烧制模拟过程中的冷却速率可以提高钯银铟锡镓金属陶瓷合金的硬度，而无需对合金进行额外的热处理。
