Study On Microstructures And Wear Properties Of ZrTi Alloys For Dental Application

Dental repair technique is the basic guarantee of oral health, which is the prerequisite to ensure peoples quality of life. However, the development of materials is the basis for the dental restoration. With the continuous development of dental restorative materials, a large number of metals and their alloys are widely used in dental restoration, owing to their good mechanical properties and biological characteristics. Commercially pure Ti and Ti-6Al-4V alloy are most commonly used titanium materials for implant applications. However, the insufficient strength and poor wear resistance of unalloyed titanium was often complained. Furthermore, more and more concerns are raised due to the toxicity of aluminum and vanadium released from Ti-6Al-4V alloy. Their uses in clinical applications are greatly restricted.In this thesis, alloying method was used to design new alloys. Ti is applied as the second component. Cu and Ag were added as minor alloying elements. Optical microscope, XRD, SEM, TEM, friction and wear testing machine were applied to study the microstructure, phase composition, mechanical properties and wear characteristics of ZrTi solid solution alloys and their thermal oxidation coatings.The investigations have shown that Zr-20Ti, Zr-40Ti, Zr-40Ti-6Ag and Zr-40Ti-2Cu alloys were consisted of a single a-phase. With the addition of Cu, Zr-40Ti revealed refined microstructure, which was composed of almost all thin twin-chip layers, slightly high micro-hardness, increased compressive strength, but nearly unchanged plasticity. After adding Ag, the microstructure of Zr-40Ti was obviously refined, micro-hardness was improved, but the plasticity and compressive strength decreased.Thermal oxidation experiments show that ZrTiO4ceramic coating can be synthesized in situ in thermal oxidation method, increasing the micro-hardness significantly. After oxidized for2h, the oxide coatings thickness on Zr-20Ti and Zr-40Ti was between10um and20um. The binding force was up to50N, superior to those formed by plasma spraying, magnetron sputter ion plating and micro-arc oxidation method.Wear tests revealed that the steady friction coefficients of Zr-20Ti、Zr-40Ti varied slightly while the volume wear rates decreased to1/3compared with pure Ti, the wear resistance has been greatly improved. With the addition of Cu, Ag, Zr-40Ti-6Ag and Zr-40Ti-2Cu showed the reduced steady friction coefficients, volume wear rates and increase of wear resistance. After oxidized for2h, the volume wear rates of oxide coatings decreased as much as1/10and the wear resistance increased highly. The applied load had influence on the wear mechanism of solid solution alloys. They exhibited light oxide wearing and abrasive wearing under5N; In ION load, Zr-20Ti alloy coexisted abrasive wear, adhesive wear and oxidation wear, Zr-40Ti, Zr-40Ti-2Cu, Zr-40Ti-6Ag alloys exhibited both abrasive wear and oxidative wear. The wear mechanism for oxide coatings were adherence wearing in both loads.