Alexandra Banu

Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resistance behavior of two titanium aluminides of α2 + γ(Ti3Al + TiAl) and orthorhombic Ti2NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti2NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.

Study on Processing of Titanium Aluminide Alloy Using Electrical Discharge Machining

Currently there is a continuous extension of application areas of titanium aluminides but their processing encounters a number of difficulties such as the precision of machining and modifying the properties of the surface layer. In the specialist literature [1, 2, 4, 7] different authors address the processing of these materials by conventional methods. In this context, this paper aims at finding the optimal regimes for the electrical discharge machining (EDM) of titanium aluminides Ti-40Al-5NB-3V and provides the analysis of the process parameters effect on cutting through wire EDM technological characteristics. In the case of wire EDM a relatively good output has been obtained as well as very good roughness of the processed surfaces. On the contrary, when considering the die sinking edm, due to very small output, several experimental measurements were performed on three machines – Sodick, ONA and ELER. Based on the experimental data, it has been established that the best output is to be obtained by reverse polarity machining.

Micro Reactor For Chlorophenols Electrocathalytic Oxidation

Chlorophenols are universal priority pollutants listed by all Environmental Agencies. The removal of chlorophenols from contaminated waters is carried out by microbiological and chemical methods. In this work is presented a combination of three methods that are electrochemical oxidation, electrochemical reduction and photo-Fenton-oxidation. Results performed in a micropilot reactor showed that it is feasible to degrade chlorophenols by these combined methods, with a removal rate of 82%, at a current density of 6.66 Adm -2 . The current efficiency was calculated and the results indicated that this combined method is more efficient that separated ones (electrochemical oxidation or reduction).

High Temperature Behavior of Two Titanium Aluminides for Blade Engine Applications. Preliminary Study

The developmental tendencies in obtaining high performance of gas turbines are chiefly connected with an increase in the engine’s capacity, its efficiency, lifetime, and reduce the deleterious emissions. One way to achieve these targets is the usage of lighter and stronger materials and enhancing the method of parts manufacture. The present work is a part of a national project whose main goal is to develop a new class of light alloys-coatings structures for aerospace, energy and the automotive industry, fated to reduce pollution and to contribute to a friendlier environment. One way to enhancing the high temperature response against the severe environmental conditions, is by development of titanium aluminides with increased niobium content and two different structures: α2 + γ (Ti2Al + TiAl), and Orto AlNbTi2. The paper present the preliminary results on mechanical properties modification because of niobium content increased from 10 at.% to 25% and on beneficial influence of Thermal barrier coating.

Aspects Regarding Competence, Training and Awareness Requirements for the Environmental Management System Certification Audit

One of the requirements of ISO 14001 is that the organization must ensure that any person, including personnel working for and on behalf of organization, that have the potential to cause significant environmental impacts is well trained and competent. The personnel competencies can be defined by education, training and/or appropriate experience. In this regard, this paper briefly present requirements and specific documents for proper audit of requirement 4.4.2 that will constitute evidence of practical implementation of SR EN ISO 14001:2005.

Gamma Titanium Aluminides Behavior at High Temperature Static Short-Term Stress

Today conventional titanium-based alloys represent one third of the weight of modern aircraft engines and, are the second most used engine material following Ni-based superalloys. [1] Titanium aluminide alloys based on intermetallic phases γ (TiAl) and α2 (Ti3Al) and the most recent – orthorhombic titanium aluminide, are widely recognized as having the potential to meet the design requirements for high temperature applications. The outstanding thermo-physical and mechanical properties of these materials rely mainly on the strongly ordered nature and the directional bonding of the compounds. These involve: high melting point, above 1460°C, low density of 3,9-5 g/cm3, according the alloying degree, high elastic modulus (high stiffness), high yield strength and good creep resistance at high temperature, low diffusion coefficient, good structural stability at high temperature. The main objective of our paper are focussed on the short-term mechanical properties if Titanium niobium aluminide at 850°C. High temperatures mechanical properties evaluation was performed by tensile testing at temperature of 850°C on universal static and dynamic testing machine Instron 8802, equipped with high temperature system, for maximum 1000°C, and extensometer with a measuring basis of 40 mm. The mechanical tensile test was performed according the ASTM E8, with control of deformation and a testing rate of 10-4 mmsec.-1. Short-term behavior request of the support uncovered alloys, at 850°C has proved to be modest and it seems obvious that the alloys based on titanium aluminides cannot be used without protective coatings. Key words: titanium aluminides, high temperatures, mechanical properties