Fretting Corrosion Behavior of Experimental Ti-20Cr Compared to Titanium

Bond strength of commercial veneering porcelain to experimental cast Ti-Cr alloy

This study evaluated bond strengths of three commercial veneering porcelains to experimental cast titanium-chromium (Ti-Cr) alloy and commercially pure titanium (cp-Ti) via three-point bending test. After the bending test, the fractured specimens were analyzed using an electron probe microanalyzer (EPMA). The Ti-Cr specimens showed lower bond strengths than the cp-Ti specimens, irrespective of the layering porcelain material; however, all the strengths exceeded the minimum requirement of ISO 9693-1:2012 (>25 MPa). EPMA revealed that titanium and/or chromium elements were detected on the debonded porcelain surface of the Ti-Cr and cp-Ti specimens in the case of the higher bond strength. Contrastingly, the residual porcelain was retained on the metallic surface in the case of the lower bond strength. Although porcelain bonding to the titanium alloy is influenced by porcelain type, the Ti-Cr alloy could be feasible for porcelain-fused-to-metal restorations.

Corrosion of Metallic Biomaterials: A Review

Metallic biomaterials are used in medical devices in humans more than any other family of materials. The corrosion resistance of an implant material affects its functionality and durability and is a prime factor governing biocompatibility. The fundamental paradigm of metallic biomaterials, except biodegradable metals, has been "the more corrosion resistant, the more biocompatible." The body environment is harsh and raises several challenges with respect to corrosion control. In this invited review paper, the body environment is analysed in detail and the possible effects of the corrosion of different biomaterials on biocompatibility are discussed. Then, the kinetics of corrosion, passivity, its breakdown and regeneration in vivo are conferred. Next, the mostly used metallic biomaterials and their corrosion performance are reviewed. These biomaterials include stainless steels, cobalt-chromium alloys, titanium and its alloys, Nitinol shape memory alloy, dental amalgams, gold, metallic glasses and biodegradable metals. Then, the principles of implant failure, retrieval and failure analysis are highlighted, followed by description of the most common corrosion processes in vivo. Finally, approaches to control the corrosion of metallic biomaterials are highlighted.

A Literature Review Study on Atomic Ions Dissolution of Titanium and Its Alloys in Implant Dentistry

This review of literature paper was done in order to conduct a review of the literature and an assessment of the effects of titanium implant corrosion on peri-implant health and success in the oral environment. This paper evaluates and critically reviews the findings of the multiple in-depth in vivo and in vitro studies that are related to corrosion aspects of the titanium and its alloys. A literature survey was conducted by electronic search in Medline and studies that were published between 1940 and August 2018 were selected. The search terms used were types of corrosion, corrosion of titanium implants, titanium corrosion, metal ion release from the titanium implants, fretting and pitting corrosion, implant corrosion, peri implantitis, and corrosion. Both in vivo and in vitro studies were also included in the review. The search and selection resulted in 64 articles. These articles were divided on the basis of their context to different kinds of corrosion related to titanium dental implants. It is evident that metal ions are released from titanium and titanium alloy dental implants as a result of corrosion. Corrosion of implants is multifactorial, including electrical, chemical, and mechanical factors, which have an effect on the peri-implant tissues and microbiota. The literature surveyed showed that corrosion related to titanium and its alloys has an effect on the health of peri-implant soft and hard tissue and the long term survival of metal dental implants. It can be concluded that presence of the long-term corrosion reaction along with continuous corrosion leads to the release of ions into the peri-implant tissue but also to a disintegration of the implant that contribute to material fatigue and even fracture of the abutments and implant body or both. This combined impact of the corrosion, bacterial activity, chemical reactions, and functional stresses are to be looked at as important factors of implant failure. The findings can be used to explore the possible strategies of research to investigate the biological impact of implant materials.

Research on the Single Grit Scratching Process of Oxygen-Free Copper (OFC)

Single grit scratching is a basic form of material removal for many processes, such as grinding single point diamond turning and coating bonding performance tests. It has been widely used in the study of micro-scale and nano-scale material removal mechanisms. In this study, single grit linearly loading scratching tests were carried out on a scratching tester. A Rockwell indenter made of natural diamond was selected as the tool used, and the material of the workpiece was oxygen-free copper. Scratch topography was measured using a super-depth microscope to analyze the material deformation of the scratching process. A single grit scratching simulation has been developed by AdvantEdge™ to comprehensively study the material deformation of scratching processes. A material constitutive model and friction model were acquired using a quasi-static uniaxial compression experiment and a reciprocating friction test, respectively. These two models were used as the input models in the finite simulations. The simulated scratching forces aligned well with the experimental scratching forces, which verified the precision of the simulation model. Since only the scratching force could be obtained in the scratching experiment, the plastic strain, material flow, and residual stress of the scratching were further analyzed using simulations. The results showed that the plastic strain of the workpiece increased with the increase in scratching depth, and further analysis showed that the workpiece surface was distributed with residual compressive stress and the sub-surface was distributed with residual tensile stress in single grit scratching.

Fretting Wear Damage Mechanism of Uranium under Various Atmosphere and Vacuum Conditions

A fretting wear experiment with uranium has been performed on a linear reciprocating tribometer with ball-on-disk contact. This study focused on the fretting behavior of the uranium under different atmospheres (Ar, Air (21% O₂ + 78% N₂), and O₂) and vacuum conditions (1.05 and 1 × 10⁻⁴ Pa). Evolution of friction was assessed by coefficient of friction (COF) and friction-dissipated energy. The oxide of the wear surface was evaluated by Raman spectroscopy. The result shows that fretting wear behavior presents strong atmosphere and vacuum condition dependence. With increasing oxygen content, the COF decreases due to abrasive wear and formation of oxide film. The COF in the oxygen condition is at least 0.335, and it has a maximum wear volume of about 1.48 × 10⁷ μm³. However, the COF in a high vacuum condition is maximum about 1.104, and the wear volume is 1.64 × 10⁶ μm³. The COF in the low vacuum condition is very different: it firstly increased and then decreased rapidly to a steady value. It is caused by slight abrasive wear and the formation of tribofilm after thousands of cycles.