Search

Objective To evaluate the influence of different heat treatments on the corrosion behavior of a new Pd⁃ Ag⁃In⁃Ga alloy. Methods The corrosion of a new Pd⁃Ag⁃In⁃Ga alloy was tested according to ISO 10271：2001/cor.1: 2005(E). Taken as comparison, a commercial high⁃palladium alloy (Spartan® Plus) was also employed in the study. For electrochemical corrosion test, the open ⁃circuit potential (Eocp) and potentiodynamic polarization curve were recorded and then the electrochemical parameters, namely corrosion potential (Ecorr) and corrosion current density (Icorr) calcu⁃ lated. The surfaces of the specimens that before and after corrosion test were observed by scanning electron microscopy (SEM). Results Both of the high ⁃ palladium alloys had lower corrosion tendency and higher corrosion resistance by heat treatment in the ISO 10271 electrochemical corrosion test. For both alloys, heat treatment at 500 ℃ was found to be effective in improving the corrosion resistance as the best datas of electrochemical parameters (Eocp, Ecorr, Icorr) were detected among the four temperature groups. However, no evidence showed that there was significant difference in corrosion resistance between the two alloys. Comparison of surface morphology of the specimens before and after electro⁃ chemical experiments by SEM demonstrated that all groups of the two alloys were visible of pitting corrosion and crevice corrosion phenomenon that gradually became less with increasing heat treatment temperature. Horizontal comparing among the groups of the two alloys, no apparent differences in the distribution of pitting and crevice corrosion was found. Conclusion The variation in compositions of high⁃palladium alloys did not cause significant difference in corro⁃ sion behavior due to the identical palladium matrix. The similarity in corrosion behavior among the two high⁃palladium alloys might be attributed to the predominant palladium content.

Objective The purpose of this study was to investigate the influence of cryogenic treatment and age- hardening heat treatment on the micro-Vicker' s hardness of palladium -silver dental alloys. Methods A low-gold content dental casting ahoy composed of Ag-Pd-Cu-Au was prepared for this study. Experimental specimens according to standard requirements were prepared following a standard dental laboratory casting procedure, cast specimens were heated to 900 °C and quenched in ice water. The specimens were then divided into 4 groups. They were subsequently subjected to different treatments, including age-hardening heat treatment, cryogenic treatment, heat treatment combined with cryogenic treatment. The non-treated group was used as control. The micro-Vicker's hardness value was examined. The significance of correlation was analyzed. Results The micro-Vicker' s hardness of specimens after age-hardening heat treatment, cryogenic treatment, heat treatment combined with cryogenic treatment increased by 129%, 13% and 141%, respectively, compared with that of the non-treated control group. Conclusion Age-hardening heat treatment and cryogenic treatment were effective in elevating the hardness of Ag-Pd-Cu-Au alloy. [ABSTRACT FROM AUTHOR]