ABSTRACT
PURPOSE: In this study, brazing characteristics of ZrO2 and Ti-6Al-4V brazed joints with increasing temperature were investigated. MATERIALS AND METHODS: The sample size of the ZrO2 was 3 mm x 3 mm x 3 mm (thickness), and Ti-6Al-4V was 10 mm (diameter) x 5 mm (thickness). The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under 5 x 10(-6) torr atmosphere, while the brazing temperature was changed from 700 to 800degrees C for 30 min. RESULTS: The experimental results shows that brazed joint of ZrO2 and Ti-6Al-4V occurred at 700 - 800degrees C. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of ZrO2 and Ti-6Al-4V bonded interfaces decreased with brazing temperature. CONCLUSION: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between ZrO2 and Ti did not occur enough.
Subject(s)
Alloys , Atmosphere , Dental Implants , Hot Temperature , Joints , Sample Size , Titanium , Vacuum , ZirconiumABSTRACT
O objetivo deste trabalho foi comparar, por meio de teste de microdureza e técnicas de caracterização metalúrgica, que inclui a metalografia, microscopia óptica, microscopia eletrônica de varredura (MEV) e espectroscopia por dispersão de energia (energy dispersive spectroscopy EDS), propriedades mecânicas e metalúrgicas de juntas soldadas pelos métodos TIG e brasagem em uma liga odontológica à base de Ni-Cr (FIT-CAST SB). As regiões estudadas em cada amostra foram o metal de base (MB), a zona termicamente afetada (ZTA) e a zona de fusão (ZF). Foram confeccionados 40 corpos-de-prova cilíndricos, em forma de bastão, com 2,5mm de diâmetro e 18,0mm de comprimento, obtidos apartir de fundição odontológica por centrifugação (técnica da cera perdida). Foram separados vinte cilindros para cada técnica, que após a soldagem formaram grupos de dez amostras para cada procedimento. A microestrutura do MB apresentou-se como uma matriz de uma solução sólida à base de Ni-Cr contendo um típico arranjo dendrítico de estrutura eutética. A liga apresentou precipitados metálicos na região interdendrítica da estrutura eutética. A análise química semi-quantitativa obtida através da técnica de EDS apresentou resultados compatíveis com a composição química quantitativa fornecida pelo fabricante da liga. Na brasagem, o MB e a ZF apresentaram microestruturas distintas. A ZF apresentou uma morfologia dendrítica grosseira com a presença de precipitados e porosidades. A análise química semi quantitativa por EDS da ZF mostrou-se bastante semelhante aos resultados obtidos para o MB...
The purpose of this study was to compare, by means of microhardness testing and metallurgical characterization techniques as metallography, optical microscopy, scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS), mechanical and metallurgical properties of welded joints by TIG and brazing methods in a dental alloy based on Ni-Cr (FIT-CAST SB). The studied regions in each sample were the base metal (MB), the heat affected zone (ZTA) and the fusion zone (ZF). Forty cylindrical bodies-of-proof, stick-shaped, with 2.5mm diameter and 18.0mm in length were made from dental casting by centrifugation (lost wax technique). Twenty cylinders were used for each technique, which formed, after the welding, groups of ten samples for each procedure. The microstructure of the MB is presented as a matrix of a solid solution based on Ni-Cr with a typical dendritic arrangement of eutectic structure. The alloy presented metallic precipitates in the interdendritic region of the eutectic structure. The semiquantitative chemical analysis obtained by EDS technique showed results consistent with the quantitative chemical composition provided by the alloy manufacturer. In the brazing method, the MB and ZF showed different microstructures. The ZF showed a rough dendritic morphology with the presence of precipitates and porosities. The semiquantitative chemical analysis by EDS of the ZF had very similar results to those obtained for the MB...
Subject(s)
Chromium Alloys , Nickel , Dental Soldering/instrumentation , Dental Soldering/methods , Tungsten , Hardness Tests , Microscopy , Microscopy, Electron, ScanningABSTRACT
The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band.