• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.6
• /
• pp.740-750
• /
• 2006

Statement of problems. In an attempt to reduce screw loosening, dry lubricant coatings such as pure gold or tefron have been applied to the abutment screw. However, under repeated tightening and loosening procedures, low wear resistance and adhesion strength of coating material produced free particles on the surface of abutment screw and increased frictional resistance resulting in screw tightening problems. Purpose. The aim of this study was to compare friction coefficient, adhesion strength, vickers hardness and evaluate coating surface of titanium alloy specimens coated with TiN(titanium nitride), ZrN(zirconium nitride) and WC(tungsten carbide). Material and method. Titanium alloy(Ti-6Al-4V) discs of 12mm in diameter and 1mm in thickness divided into 4 groups. TiN, ZrN and WC was coated for the specimens of 3 groups respectively, and those of 1 group were not coated. Each group was made up of 4 specimens. In this study, sputtering method was used among the PVD(Physical Vapor Deposition) techniques available for TiN, ZrN and WC coatings. Friction coefficient, adhesion strength, vickers hardness and coating surface of 4 groups were measured. Results. 1. For all three coating conditions, friction coefficient was significantly decreased. Especially, ZrN coated surface showed the lowest value. $TiN(0.39{\pm}0.02)$, $ZrN(0.24{\pm}0.01)$, $WC(0.31{\pm}0.03)$. 2. TiN coating showed the highest adhesion strength, however ZrN coating had the lowest value. $TiN(25.3N{\pm}1.6)$, $ZrN(14.8N{\pm}0.6)$, $ WC(18.4N{\pm}0.7)$. 3. Vickers hardness of all three coatings was remarkably increased as compared with that of none coated specimen. TiN coating had the highest Vickers hardness, however WC coating showed the lowest value. $TiN(1865.2{\pm}33.8)$, $ZrN(1814.4{\pm}18.6)$, $WC(1008.5{\pm}35.9)$. 4. The ZrN or WC coated specimen showed a homogeneous and smooth surface, however the rough surface with defects was observed for TiN coating. Conclusions. When TiN, ZrN and WC coating applied to the abutment screw, frictional resistance would be reduced, as a result, the greater preload and prevention of the screw loosening could be expected.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.5
• /
• pp.675-686
• /
• 2007

Statement of problem: Titanium nitride(TiN) coatings are the most general and popular coating method and used to improve the properties of metallic surface for industrial purposes. When TiN coating applied to the abutment screw, frictional resistance would be reduced, as a results, the greater preload and prevention of the screw loosening could be expected. Purpose: The purpose of this study was to investigate mechanical properties of TiN coated film of various coating thickness on the titanium alloy surface and to evaluate proper coating thickness. Material and method: 95 Titanium alloy (Ti-6Al-4V) discs of 15 mm in diameter and 3 mm in thickness were prepared for TiN coating and divided into 7 groups in this study. Acceding to coating deposition time (CDT) with TiN by using Arc ion plating, were divided into 7 groups : Group A (CDT 30min), Group B (CDT 60min), Group C (CDT 90min), Group D (CDT 120min), Group E (CDT 150min), Group F(CDT 180min) and Group G (no CDT) as a control group. TiN coating surface was observed with Atomic Force Microscope(AFM), field emission scanning electron microscopy(FE-SEM) and examined with scratch tester, wear tester. Result: 1. Coating thickness fir each coated group was increased in proportion to coating deposition time. 2. Surface of all coated groups except Group A was homogeneous and smooth. However, surface of none coated Group G had scratch. 3. Adhesion strength for each coated group was increased in proportion to coating deposition time. 4. Wear resistance for each coated group was increased in proportion to coating deposition time. 5. Surface roughness in Group A, B, C was increased in proportion to coating deposition time. But, surface roughness in Group D, E, F was showed decreased tendency in proportion to coating deposition time. Conclusion: According to coating deposition time, mechanical properties of TiN coated film were changed. It was considered that 120 minutes coating deposition time ($1.32{\mu}m$ in coating thickness) is necessary.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.6
• /
• pp.727-735
• /
• 2005

Statement of problem. Platform switching in implant prosthesis has been used for esthetic and biological purpose. But there are few reports for this concept. Purpose. The purpose of this study is evaluation of platform switching in wide implant by three dimensional finite element analysis. Materials and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for Osstem implant system. Three-dimensional finite element models were developed for (1) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with wide cemented abutment, titanium alloy abutment screw, and prosthesis (2) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with regular cemented abutment, titanium alloy abutment screw and prosthesis(platform switching) was made for finite element analysis. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized to 650N, and round and flat type prostheses were loaded to 200 N. Four loading offset point (0, 2, 4, 6 mm from the center of the implants) were evaluated. Models were processed by the software programs HyperMesh and ANSA. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView were used for post processing. Results. The results from experiment were as follows; 1. von Mises stress value is increased in order of bone, abutment, implant and abutment screw. 2. von Mises stress of abutment screw is lower when platform switching. 3. von Mises stress of implant is lower when platform switching until loading offset 4 mm. 4. von Mises stress of abutment is similar between each other. 5. von Mises stress of bone is slightly higher when platform switching. Conclusion. The von Mises stress pattern of implant components is favor when platform switch ing but slightly higher in bone stress distribution than use of wide abutment. The research about stress distribution is essential for investigation of the cortical bone loss.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.1
• /
• pp.45-51
• /
• 1989

In metal cutting various types of chips are produced in consequence of cutting conditions. According to the type of chips the cutting mechanism is to be changed. Most of the cutting theory is based on the continuous chip because of its convenient analysis, but the occurrence of the saw-toothed chip depends upon the workpiece and/or the cutting conditions, one of which is titanium alloy used widely. Nowadays titanium alloys are used widely with the rapid development of aerospace structural engineering application, whereas the theory of cutting mechanism has not been established yet, and the formatting process has not been understood satisfactorily, either. Unfortunately several misconceptions, conflicting statements and statements needing further clarifi- cation are also found. In this paper an attempt is made to clarify the formation process of saw-toothed chips which are to be produced during the orthogonal cutting process of titanium alloys. They were machined at low speed to avoid the rapid tool wear. We observed the SEM-photographs of chips taken at the quick-st- opping device. It is hoped that a rational model of the mechanics of cyclic chip formation can be developed. The results obtained are as follows. 1. When a saw- toothed chip is formed, the shear band begins at the primary shear zone and trans- fers to the free surface, so that a segment is produced and it is completed by upsetting between the formatting segment and the formatted segment. 2. As the rake angle or the clearance angle increases in the machining of the titanium alloy, the chip approaches to that of the continous type. 3. When the rake angle and the clearance angle are increased the shear energy and the unit friction energy decrease, which shows the same aspect as that of the continuous chip.

• Journal of Surface Science and Engineering
• /
• v.32 no.2
• /
• pp.134-143
• /
• 1999

The effects of silicon on galvannealing behavior of interstitial-free (IF) steels were studied. The growth rate of the Fe-Zn alloy layer was retarded as silicon in the steel added. Titanium in steel strongly favors Fe-Zn reaction, in particular outburst structures, whereas silicon inhibit them. Cross-sectional and planar views of galvannealed coatings were investigated to characterize alloy phase development. A possible mechanism to explain the retardation effect of silicon is discussed in terms of concentration on surface and inhibition layer.

• Korean Journal of Materials Research
• /
• v.24 no.7
• /
• pp.381-387
• /
• 2014

The ${\beta}$-transus temperature in titanium alloys plays an important role in the design of thermo-mechanical treatments. It primarily depends on the chemical composition of the alloy and the relationship between them is non-linear and complex. Considering these relationships is difficult using mathematical equations. A feed-forward neural-network model with a back-propagation algorithm was developed to simulate the relationship between the ${\beta}$-transus temperature of titanium alloys, and the alloying elements. The input parameters to the model consisted of the nine alloying elements (i.e., Al, Cr, Fe, Mo, Sn, Si, V, Zr, and O), whereas the model output is the ${\beta}$-transus temperature. The model developed was then used to predict the ${\beta}$-transus temperature for different elemental combinations. Sensitivity analysis was performed on a trained neural-network model to study the effect of alloying elements on the ${\beta}$-transus temperature, keeping other elements constant. Very good performance of the model was achieved with previously unseen experimental data. Some explanation of the predicted results from the metallurgical point of view is given. The graphical-user-interface developed for the model should be very useful to researchers and in industry for designing the thermo-mechanical treatment of titanium alloys.

• Journal of the Korean Society for Heat Treatment
• /
• v.32 no.2
• /
• pp.68-73
• /
• 2019

${\alpha}$-titanium alloy has a relatively low heat treatment characteristic and it is mainly subjected to heat treatment for residual stress, recovery or dynamic recrystallization. In this study, commercially pure titanium hollow castings was fabricated by gravity casting. Heat treatments were carried out at $750^{\circ}C$, $850^{\circ}C$ and $950^{\circ}C$ to investigate the effect of post-heat treatment on microstructure and mechanical properties. Beta-transus temperature ($T_{\beta}$) was about $913^{\circ}C$, and equiaxed microstructure was shown at temperature below $T_{\beta}$ and lath-type microstructure at temperature above $T_{\beta}$. Microstructure and mechanical properties did not show any significant difference in the direction of solidification for titanium hollow billet, so it can be seen that it was a well-made material for extrusion process. The optimum heat treatment condition of hollow billet castings for the seamless tube production was $850^{\circ}C$, 4 hr, FC, indicating a combination of equiaxed microstructure and appropriate mechanical properties.

• Journal of the Korean Society for Heat Treatment
• /
• v.37 no.5
• /
• pp.247-254
• /
• 2024

Metastable β titanium alloys have been used in implants due to their high specific strength and excellent corrosion resistance. However, the high cost of β-stabilizing elements limits the application of metastable β titanium alloys. Consequently, research has been conducted on low-cost metastable β titanium alloys using relatively inexpenisve β-stabilizing elements such as Mo and Fe. This study analyzes the wear resistance of Ti-5Mo-xFe (x=2,4 wt%) alloys, designed and manufactured as low-cost metastable β titanium alloys. The wear mechanisms of Ti-5Mo-xFe alloys were identified through ball-on disk testing and observation of the worn surfaces. Additionally, the influence of Fe addition on the microstructure and the resulting changes in wear resistance were examined. The wear resistance of the Ti-5Mo-xFe alloys were evaluated in comparison to the Ti-6Al-4V ELI alloy.

• Journal of Technologic Dentistry
• /
• v.27 no.1
• /
• pp.73-78
• /
• 2005

The surface-reacted layer of titanium castings greatly affects their mechanical properties. This study analyzed the interfacial zone of Ti-20%Zr-5%Cr alloy castings obtained from phosphate bonded investment and examined the relationship between the surface-reacted layer and hardness. The Vickers hardness of cast disks were tested at 20$\mu m$ intervals from the surface to 120$\mu m$ in depth. The cross-section was observed metallurgically, and line profile of the reacted layer was conducted under the EDX. The surface-reacted layer of Ti-20%Zr-5%Cr alloy is showed a similar tendency to Ti-6%Al-4%V alloy in thickness, and also Si diffusion in multiple reacted layer of Ti-20%Zr-5%Cr alloy is less than cp Ti and similar to Ti-6%Al-4%V alloy. The Vickers hardness in the surface layer was greater than in the inner part, and the Vickers hardness of Ti-20%Zr-5%Cr alloy ranged 650 to 390 and cp Ti ranged 810 to 160, Ti-6%Al-4%V alloy ranged 710 to 530 respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.10a
• /
• pp.328-331
• /
• 2009

Microstructural evolution of alpha and beta phases during dynamic globularization of near-beta Ti-13Nb-13Zr alloy was investigated to determine the optimum processing conditions. The submicrocrystalline alloy sheet with ${\sim}80%$ of high-angle grain boundaries was produced utilizing dynamic globularization at temperature of $600^{\circ}C$, equivalent strain rate of $10^{-1}\;s^{-1}$ and strain of 1.4. The refined structure with the gain size of ${\sim}0.4{\mu}m$ showed 25-60% enhanced mechanical compatibility as compared to those of the conventional mill-annealed or solution treated and aged microstructures.