Hardening effect of pre- and post-firing heat treatment for a firing-simulated Au-Pd-In metal-ceramic alloy

Abstract

The hardening effect of the pre-and post-firing heat treatments and their dual treatment was examined for a firingsimulated Au-Pd-In metal-ceramic alloy to determine if an additional post-firing heat treatment is effective in the hardening of an Au-Pd-In metal-ceramic alloy as well as to compare the hardening effects of pre-and post-firing heat treatments for a firing-simulated Au-Pd-In metal-ceramic alloy. The postfiring heat treatment was much more effective than the prefiring heat treatment or dual treatments. The hardening effect of the pre-and post-firing heat treatments was caused by the induction of fine grain interior precipitation. In the pre-firing heat-treated specimen after casting, the apparent hardening was achieved during simulated porcelain firing, but an additional post-firing heat treatment did not introduce severe grain interior precipitation, resulting in very weak hardening. In the as-cast specimen without the pre-firing heat treatment, apparent hardening by grain interior precipitation was achieved only by post-firing heat treatment and not by simulated porcelain firing.

Effect of ice-quenching on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulation

“…2). Such rapid recovery in the hardness according to the cooling rate control during the porcelain firing process was also reported for Pd-Au-In-Ag and Pd-Ag-Au-Sn alloys, which had undergone a pre-softening heat treatment before porcelain firing 7,11) . From the above, if the readjustment is done for the ice-quenched metal substructure after degassing, it will increase the efficiency of processing without affecting the mechanical properties of the final prosthesis.…”

“…1), which is a relatively fast cooling rate. Such an effective cooling rate for alloy hardening was reported to vary according to the composition of the alloys 7,[10][11][12] . From the apparent hardening during cooling, the alloy was believed to have undergone precipitation or atomic ordering during cooling.…”

“…To verify this, a Pd-Au-Zn alloy, which is one of the representative dental alloys for metal-ceramic crowns, was used in the present study. A previous study with a 50.37Pd-30.61Au-9.92In-6.09Ag (at%) alloy with minor ingredients reported that pre-softening heat-treatment of the alloy induced precipitation more actively during the porcelain firing process, resulting in apparent hardening 7) . Similarly, in the present study, the alloy softened by ice-quenching was expected to recover its hardness during the remaining firing process for bonding porcelain.…”

Change in hardness of an as-cast and softening heat-treated low-gold-content alloy for bonding porcelain by simulated porcelain firing and its mechanism

“…Through the remainder of the firing process, the hardness decreased gradually, even though the peak intensity of the β precipitates increased further. FE-SEM, which showed the microstructural coarsening of the β precipitates through subsequent firing process, indicated that softening resulted from the release of lattice strain by the reduced interphase boundaries between the coarsened β precipitates and surrounding matrix [3,5].…”

“…Then during cooling to room temperature, the alloys can be hardened to some extent by atomic ordering or precipitation of the alloy components [1,2]. Therefore, depending on the composition, the alloy becomes much softer after several porcelain-firing cycles [3][4][5].…”