Corrosion Resistance Of Titanium Alloys Research Articles

Enhancement of the corrosion resistance of titanium alloys of the Ti-Al-Mo-V system by carbonitriding

We study the regularities of formation of coatings on titanium alloys of the Ti-Al-Mo-V system in the process of saturation in carbon-and-nitrogen-containing media (with an oxygen content of at most 0.01–0.0005 vol.%) and their corrosion-electrochemical behavior in an 80% aqueous solution of sulfuric acid. The difference between the phase compositions of the coatings formed in different temperature ranges of saturation is revealed. Thus, nitride coatings are formed on the surface at temperatures below 1100°C and carbonitride coatings are formed above 1100°C. It is shown that the physicochemical characteristics of nitride coatings formed in carbon-and-nitrogen-containing media are better than the corresponding characteristics of nitride coatings obtained by nitriding for the same temperature, time, and gas-dynamic parameters of saturation. As the content of cubic δ-nitride in the coating increases, the corrosion characteristics of the surface after saturation in carbon-and-nitrogen-containing media increase. Despite a significant surface roughness of carbonitride coatings, their corrosion resistance is high.

Electrochemical behaviour of titanium alloys in artificial saliva

Titanium alloys are used in odontology applications owing to their excellent biocompatibility. The corrosion resistance of titanium alloys is an important component of their biocompatibility. In this study, the electrochemical corrosion resistance of Ti6Al4V, Ti6Al7Nb, Ti6Al2Nb1Ta1Mo, Ti5Al2,5Fe and commercial titanium in Afnor saliva was investigated. Maintaining titanium and Ti6Al7Nb alloy in Afnor saliva for 7 days results in the formation of a protective layer, the resistance of which is high and could be comparedwith that of a passive layer resulting from electrochemical treatment. The replacement of vanadium with niobium or iron favours the passivation, thus increasing the corrosion resistance.

Research progress on laser surface modification of titanium alloys

Recent developments on laser surface modification of titanium and its alloys are reviewed. Due to the intrinsic properties of high coherence and directionality, laser beam can be focus onto metallic surface to perform a broad range of treatments such as remelting, alloying and cladding, which are used to improve the wear and corrosion resistance of titanium alloys. In addition, the fabrication of bioactive films on the surface of titanium alloys to improve their biocompatibility can be performed by the method of laser ablation deposition. The effect of some laser processing parameters on the resulting surface properties of titanium alloys is discussed. The problems to be solved and the prospects in the field of laser modification of titanium and its alloys are elucidated.

Application of artificial neural networks for modelling correlations in titanium alloys

This paper is dedicated to the application of artificial neural networks (ANN) in titanium alloys research, including: (i) time–temperature transformation (TTT) diagrams for titanium alloys; (ii) correlation between processing parameters and properties in titanium alloys and γ-TiAl-based alloys; (iii) fatigue stress life diagrams for Ti–6Al–4V alloy; (iv) corrosion resistance of titanium alloys. For each particular case, appropriate combination of inputs and outputs is chosen. Standard multilayer feedforward networks are created and trained using comprehensive datasets from published literature. Very good performances of the neural networks are achieved. Different effects are modelled, among which are: (i) influence of the alloying elements on the transformation kinetics in titanium alloys; (ii) influence of the processing parameters, alloy composition and the work temperature on the mechanical properties for titanium alloys and titanium aluminides; (iii) influence of the microstructure, temperature, environment, surface treatment and the stress ratio on the fatigue life. The artificial neural networks models are combined with computer programmes for optimisation of the inputs in order to achieve desirable combination of outputs. Graphical user interfaces are developed for use of the models. These models are convenient and powerful tools for practical applications in solving various problems in titanium alloys.

Software products for modelling and simulation in materials science

Models and software products have been developed for modelling, simulation and prediction of different correlations in materials science, including 1. the correlation between processing parameters and properties in titanium alloys and γ-titanium aluminides; 2. time–temperature–transformation (TTT) diagrams for titanium alloys; 3. corrosion resistance of titanium alloys; 4. surface hardness and microhardness profile of nitrocarburised layers; 5. fatigue stress life ( S– N) diagrams for Ti–6Al–4V alloys. The programs are based on trained artificial neural networks. For each particular case appropriate combination of inputs and outputs is chosen. Very good performances of the models are achieved. Graphical user interfaces (GUI) are created for easy use of the models. In addition interactive text versions are developed. The models designed are combined and integrated in software package that is built up on a modular fashion. The software products are available in versions for different platforms including Windows 95/98/2000/NT, UNIX and Apple Macintosh. Description of the software products is given, to demonstrate that they are convenient and powerful tools for practical applications in solving various problems in materials science. Examples for optimisation of the alloy compositions, processing parameters and working conditions are illustrated. An option for use of the software in materials selection procedure is described.

Influence of parameters of nitrided layers on corrosion resistance of titanium alloys in solutions of acids

Influence of parameters of nitrided layers on corrosion resistance of titanium alloys in solutions of acids

Crevice and under deposit corrosion resistance of titanium alloys in highly aggressive environments

The outstanding resistance of titanium to corrosion in a wide range of aggressive conditions has been confirmed by successful applications in the chemical and process industry, (CPI), over many years. Crevice and underdeposit corrosion threshold temperatures frequently set the limits for wider application. Research to extend the capabilities of titanium and its alloys in extremes of temperature, stress and corrosion has pursued two objectives: 1. To reduce the cost of enhanced crevice corrosion resistance using palladium. 2. To provide higher strength alloys with improved crevice corrosion resistance. The first section of this paper details the range of enhanced corrosion resistance alloys containing nominally 0.05 % palladium, (ASTM Grades 16 and 17); and the measures taken to confirm that the homogeneity of composition is achieved in standard 4500 kilo ingots, now being melted for production of a full range of mill products. The second section covers the assessment and modification of alloys and the development of new alloys for specific performance goals under high stress in hostile environments. Applications are described in the offshore oil and gas extraction, desalination plant and equipment and flue gas desulphurisation plant. Reference is made to the challenges presented by emerging technologies for the safe disposal by wet oxidation of toxic substances and process effluents. Spaltkorrosionswiderstand von Titanlegierungen in stark aggressiven Umgebungen Der hervorragende Korrosionswiderstand von Titan in einem weiten Bereich von aggressiven Bedingungen wurde durch den erfolgreichen Einsatz uber viele Jahre in der Chemischen Prozesindustrie (CPI) bestatigt. Temperaturgrenzwerte fur Spaltkorrosion und Korrosion unter Ablagerungen setzen haufig die Grenzen fur weitere Anwendungen. Die Forschung zur Erweiterung der Fahigkeiten von Titan und seinen Legierungen bei extremen Temperaturen, Spannungen und Korrosionsbedingungen verfolgt zwei Ziele: 1. durch Verwendung von Palladium die Kosten eines verbesserten Spaltkorrosionswiderstandes zu reduzieren sowie 2. hoherfeste Legierungen mit verbessertem Spaltkorrosionswiderstand zur Verfugung zu stellen. Der erste Teil dieser Arbeit behandelt das Feld der Legierungen mit erhohtem Korrosionswiderstand, die nominell 0,05 % Palladium enthalten (ASTM Grade 16 und 17), und die durchgefuhrten Masnahmen zur Bestatigung, das die Homogenitat der Zusammensetzung in 4500 kg-Blocken, die zur Herstellung einer ganzen Palette von Walzprodukten erschmolzen werden, erreicht wird. Der zweite Teil behandelt die Beurteilung und Modifikation der Legierungen sowie die Entwicklung neuer Legierungen fur spezielle Anwendungsbereiche unter hohen Spannungen in aggressiven Umgebungen. Einsatzfalle im Offshorebereich, in Entsalzungsanlagen sowie in Rauchgasentschwefelungsanlagen werden beschrieben. Es wird auserdem auf die Herausforderungen im Bereich der sicheren Entsorgung durch Nasoxidation von toxischen Substanzen und Prozesabwassern eingegangen.

Effect of Alloying Elements on Anodic Polarization Properties of Titanium Alloys in Acid Solutions

The effect of Zr, Sn, Nb, Ta, Pd, N and O on the corrosion resistance of titanium alloys for medical implants was investigated by measuring the anodic polarization curves at 310 K in 5 mass% H2SO4 and 5%HCl solutions deaerated by high-purity N2 gas bubbling. The critical current density for passivation (Ic) and passive current density at 0.6 V versus SCE of the titanium alloys markedly decreased with increasing Zr, Nb, Ta, and Pd contents in the range from 5 to 20, 4 to 8, 2 to 4 and 0 to 0.2%, respectively, although Sn had an adverse effect in the range from 10 to 20 mass%. The effect of N and O on Ic was undetected. The log (Ic) value decreased linearly with increasing bond order (\barBo) value representing the covalent bond strength between Ti and the alloying elements. The passive film formed on Ti-15%Zr-4%Nb-2%Ta-0.2%Pd alloy in the 5% H2SO4 solution consisted mainly of TiO2, ZrO2, Nb2O5 and Ta2O5, as demonstrated by the electron spectroscopy for chemical analysis (ESCA). The anodic polarization properties of Ti-15%Zr-4%Nb-2%Ta-0.2%Pd and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd alloys were superior to those of the Ti-6%Al-4%V extra low interstitial alloy and SUS316L stainless steel.

生体用Ti合金の生体内模擬環境下における耐食性

The effect of alloying elements on the corrosion resistance of titanium alloys for medical implants was investigated by immersion tests in an aerated 5%HCl solution for 864 ks at 310 K and anodic polarization measurements in a phosphate buffer solution containing chloride (PBS(−)). The concentration of released Ti in the 5%HCl solution decreased with increasing Zr, Ta, and Pd contents in the range from 10 to 15, 2 to 4 and 0 to 0.2%, respectively, although Nb and Sn had an adverse effect in the range from 4 to 8 and 10 to 15 mass%, respectively. However, Zr and Sn alloying over 15% in Ti-(15∼20%)Zr-4%Nb-2%Ta-0.2%Pd and Ti-(15∼20%)Sn-4%Nb-2%Ta-0.2%Pd, respectively, showed very little difference in the concentration of released Ti, compared with those less than 15%. Especially combined alloying of 0.2%Pd and (2∼4%)Ta remarkably decreased the concentration of released Ti in the 5%HCl solution. N addition into the Pd-free Ti-10%Zr-4%Nb-2%Ta-0.1%O alloy increased the concentration of released Ti. The critical currrent density for passivation (Ic) of the titanium alloys in the PBS(−) decreased with increasing Zr, Nb, Ta and Pd contents. The Ic values in the PBS(−) decreased as those in the 5%HCl solution decreased. The concentration of released Ti from the Ti-15%Zr-4%Nb-(2∼4%)Ta-0.2%Pd and Ti-15%Sn-4%Nb-(2∼4%)Ta-0.2%Pd alloys in the 5%HCl solution were less than that from the Ti-6%Al-4%V ELI alloy by a factor of 52∼520.

Salt corrosion of titanium alloys

1. The long-term strength (1000 h) of commercial titanium alloys does not decrease under the influence of a film of NaCl at temperatures of 250° or lower. 2. With increasing testing temperatures the susceptibility of the alloys to salt increases. 3. Natural sea salt is more corrosive than NaCl at temperatures of 250° and higher. 4. The corrosion resistance of titanium alloys in contact with salt depends on the microstructure and the chemical composition of the alloy.

Room Temperature Stress Corrosion Cracking of Titanium Alloys

IT has been known for more than 10 years that titanium alloys suffer from intergranular stress corrosion cracking if they are in contact with chlorides at elevated temperatures (> 250° C), but it was only 18 months ago that Brown1 discovered that stress corrosion failures could occur at room temperature in a 3 per cent solution of sodium chloride. Titanium alloys are highly resistant to pitting attack in chloride solutions, and in order to investigate crack propagation rather than crack initiation, Brown used specimens of titanium alloy in the form of notched rectangular bars which had been fatigued in air until fine cracks had formed at the base of the notch. He found with static load tests that under plain strain conditions a 3 per cent solution of sodium chloride caused a decrease in the resistance of the alloy to the further propagation of the crack. This was a very important result, as it indicated that the stress corrosion resistance of titanium alloys under marine conditions depended on the resistance of the surface oxide on the alloy to the solution and not on the intrinsic resistance of the alloy lattice to the propagation of a stress corrosion crack which is the only really safe criterion.

Elevated Temperature Stress Corrosion Resistance of Titanium Alloys

Abstract A number of titanium alloys considered suitable for use in Mach II and III transports were tested for resistance to stress corrosion in the presence of chlorides. These included 4A1-3Mo-1V, 6A1-4V, 8A1-1M0-1V, 5A1-2.5Sn and RS-140. Samples were exposed stressed (smooth and fatigue pre-cracked) at 600, 700 and 800 F (316–427 C) 100 hours for smooth and 50 hours for precracked specimens. Welded and heat-treated specimens were among those tested. All alloys were found susceptible to stress corrosion cracking. Welding appeared to increase susceptibility, but existing fatigue cracks did not seem to increase susceptibility.

市販純チタンと比較したチタン合金の耐食性

市販純チタンと比較したチタン合金の耐食性

Corrosion Resistance of Titanium Alloys Compared With Commercially Pure Titanium

Abstract Titanium-8 percent manganese, titanium-5 percent aluminum-2½ percent tin, titanium-2 percent aluminum, titanium-6 percent aluminum, titanium-1 percent copper, and titanium-5 percent copper alloys are similar to commercially pure titanium in chemical and galvanic corrosion properties. These alloys are completely resistant to corrosion in synthetic ocean water, tap water, 1 percent sodium hydroxide, and 5 percent ferric chloride solutions. In sulfuric acid solutions saturated with air, the titanium alloys with the exception of those containing copper are resistant to corrosion in 5 percent solution at 35 C but corrode rapidly in 10 percent solution. At 60 C, these alloys are inert in 1 percent and corrode in 5 percent acid. The titanium-copper alloys usually are more resistant than commercially pure titanium to corrosion in sulfuric acid solutions and less resistant in hydrochloric acid. In contact with aluminum in 0.5 percent sulfuric acid saturated with air, titanium and the titanium-base alloys are the cathodic members of the couples. Titanium and titanium-base alloys are generally anodic when in contact with stainless steels in air-saturated 4.7, 9.3 and 17.5 percent sulfuric acid solutions but the galvanic corrosion rates are low. Furthermore, the chemical corrosion of titanium alloys is almost eliminated as a result of contact with stainless steel. 6.3.15

チタン合金の耐蝕性について

チタン合金の耐蝕性について

チタニウム合金の耐蝕性の研究（第1報）腐蝕度と自然電極電位の関係

チタニウム合金の耐蝕性の研究（第1報）腐蝕度と自然電極電位の関係