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The Influence of Chemical Surface Treatment on the Corrosion Resistance of Titanium Castings Used in Dental Prosthetics

Burnat B., Parchańska-Kowalik M., Klimek L.

Archives of Foundry Engineering

2014

Vol. 14, iss. 3

11--16

Air abrasion process is used for cleaning casting surface of prosthetic components, and to prepare the surface of these elements for the application of veneering items. Its side effect, however, is that abrasive particles are embedded in the treated surface, which can be up to 30% of the surface and it constitutes the side effect of this procedure. Such a significant participation of foreign material can not be indifferent to the properties of the surface. Embedded particles can be the place of stress concentration causing cracking of ceramics, and may deteriorate corrosion resistance by forming corrosive microlinks. In the latter cases, it would be advisable to remove elements embedded into the surface. The simplest method is chemical etching or electrochemical one. Nevertheless, these procedures should not significantly change the parameters of the surface. Among many possible reagents only a few fulfills all the above conditions. In addition, processing should not impair corrosion resistance of titanium, which is one of the most important factors determining its use as a prosthetic restoration in the mouth. The study presented results of corrosion resistance of titanium used to make prosthetic components by means of casting method, which were subjected to chemical processing designed to remove the embedded abrasive particles. The aim of the study was to investigate whether etching with selected reagents affects the corrosion resistance of titanium castings. For etching the following reagents were used: 30% HNO3 + 3% HF + H2O, HNO3+ HF+ glycerol (1:2:3), 4% HF in H2O2, 4% HF in H2O, with a control sandblasted sample, not subjected to etching. Tests demonstrated that the etching affected corrosion properties of test samples, in each case the reduction of the corrosion potential occurred - possibly due to the removal of particles of Al2O3 from the surface and activation of the surface. None of the samples underwent pitting corrosion as a result of polarization to 9 V. Values of the polarization resistance, and potentiodynamic characteristics indicated that the best corrosion resistance exhibited the samples after etching in a mixture of 4% solution of HF in H2O2. They showed very good passivation of the surface.

Plasma furnace for smelting and casting metal up to 3000 K

Zitnansky M., Demian S., Caplovic L., Rehak L., Dorschfeld R.

Archives of Materials Science and Engineering

2010

Vol. 44, nr 2

112-119

Purpose: The aim of our investigation was a development of plasma furnace for preparing castings of titanium alloy Ti64 ELI by remolding in laboratory at our research workplace. The reason of this paper writing was publishing of innovative information to the technical society. Design/methodology/approach: The objectives were achieved by solution of much research and development works in the very long time interval. The main methods used for our research was study of physic-chemical interaction between a liquid metal and surrounding atmosphere. The approach to the topic of our research was the elimination of interactions between the C, O, N and H and Ti, Al, V, Y, Zr in liquid metal. Contemporary we have solved also the acute ceramic mould for casting of perfect castings from metal of very high affinity to C, O, N and H. The main subject scope of the paper is assignee of very clean materials and much application from that. We are oriented particularly on the preparing parts of cementless total hip joint replacement (THR) and instruments for implantation. Findings: We have created the new original design of the plasma furnace for smelting and castings of high reaction of metal up to 3000 K. temperature. The main conclusion of our result was a practical using for research on very high level and for production of metal and castings from special metal in the final shape. Practical implications: It has been found that the quality of castings from Ti and Nb alloys is very good. The quality of casting was tested by metallographic analysis and by notch specimens. We have been finding out that the mass of casting can be approximately 1.00 kg. This is true statement in the first approximation if the new plasma furnace is arranged as smelting - cleaning - casting system. If the new plasma furnace is arranged as continual smelting system, than we can obtain ingot with the mass two or more kilograms. Originality/value: The design of new plasma furnace is original and also the castings from Ti, Ta and Nb alloys are in our laboratory original resultants and the metallographic analysis as well. In the case, when the castings with a good biocompatibility plays important role, this new plasma furnace can be very useful for preparing implants for body skeleton and spatial casting of material of very high affinity to elements as C, O, H, and N.