Preliminary List of Abstracts (Alphabetical Order)

THE HIGH TEMPERATURE PROTECTION COATINGS

The development of modern science and technologies increases the demand on the materials used. The use of different aircraft engine components and materials structures in aggressive environments or elevated temperature necessitate improvement of existing and development of new materials. They should be characterized by ease of production, high performance and physicochemical properties. An important role in this field also concerns appropriately selected protective coatings and modification of surface layer that significantly affect the range of applicability. They are designed mainly to improve wear and corrosion resistance in elevated temperature of operation. The tendency in the development of surface layer engineering are multilayers, based on modification of base materials with different elements. The development of a new type of surface layer modification will not only increase the efficiency of conventionally used elements but also to introduce new procedural methodology for aviation industry. More and more attention in the field is paid to CVD techniques. The presented paper focuses on combination of conventional and plasma assisted chemical vapor deposition for obtaining Al-N modified surface layer of blades. As a base material in the research, the 1H13 steel was used, that is conventionally used for production of aircraft engine compressors blades and is an excellent example for modification of elements performance parameters. Different aluminizing parameters (temperature, time) were used to investigate the diffusion characteristic and its impact on the nitriding effect. As a result, different gradient layers of Al-N-Fe type were obtained that meet different properties and performance characteristic.

In modern processes, and at the request of a steady efficiency increase, structural materials and production tools have to face more and more severe combined thermal, chemical, mechanical loads. Therefore, the choice and production of these materials with appropriate properties become a critical criterion along the industrial production process. In addition, the extension of their service life time represents a major economic objective as it enables to decrease the material costs due to replacement, but even more important, it reduces drastically the costs for the regular installation shutdown. And finally, the required quality of the produced components can be maintained and it participates to the global improvement of the industrial productivity and competitiveness. In industrial processes the criterion for choice of materials is a balance of price and properties. The use of coating on inexpensive substrates represents an alternative. For high temperature wear and corrosion resistance the use of oxide coating is suitable. Drawbacks are: Sensitivity to thermal shock, poor adhesion onto metal or alloys, high melting point, near net shape form. In this work, a two-layer system has been coated onto the substrate. The first layer (bond coat) consists of a Ni-based alloy and depends on the substrate. The second layer (top coat) was made of ZrO2/Al2O3 or YSZ (yttrium stabilized zirconia)/Al2O3 mixtures. The ceramic-based coatings were post-treated by means of solvo-thermal process. With the increase of the temperature the residual porosity in the top coat was decreased by a factor of 50% whereas the hardness increases was by approx. 40%. This solvothermal process leads also to a significant increase of the adhesion to the bond coat. Mechanical tests of solvothermally densified coatings show improved hardness and therefore better abrasion properties as well. Corrosion tests of samples in ash-deposit at high temperature and HCl-containing atmosphere show better performance in comparison to untreated samples.

Gears, due to their complex shape, carried load and required accuracy are ones of most complex aircraft engine parts. Single tooth damage usually breaks the power transmission and causes failure of the entire gear system. Adequate sustainability and guarantees of transmission is, therefore, a condition for secure operation of the whole device. Particularly high requirements for reliability are put to transmissions used in the aerospace industry. Due to the loads which are transmitted through the gears, the materials used by the manufacturer must not only have high strength but also show the abrasion resistance of the surface layer and the ductility of the core. Proper parameters matching allows to create an element that can operate at higher stresses and loads. In addition, factor strength and abrasion resistance of the surface layer has a significant impact on the life of the gear. Thermo-chemical treatment of industrial gears is a fundamental process, which gives them adequate mechanical properties regarding the loads they carry and the surface conditions of work. Among many methods of thermo-chemical treatment used in the industry, the most distinctive are innovative technologies designed to reduce process costs and being more environmentally friendly. The most promising methods in the discussed field are vacuum carburizing and high-pressure hardening, which, by their specification of work, significantly reduce the emission of CO2 and the duration of the process, without reducing the quality of the final product. The main aim of the paper is to present proper selection of heat treatment parameters and their effect on the microstructural characteristics of carburized surface layer of heavily loaded Pyrowear 53 steel gears commonly used in aircraft engine planetary gear system. Proper heat treatment parameters are crucial in programming of final material characteristics as grain size and retained austenite morphology.

Titanium and its alloys with aluminum are lightweight structural materials, which find ever-increasing use in a number of advanced aerospace, automotive and power generation applications. These materials, however, are limited in applicability by their inadequate oxidation resistance at elevated temperatures (> 500A^oC for Ti, and > 750A^oC for TiAl).This talk reviews recent advances in using state-of-the-art techniques for surface engineering of Ti, Ti-base alloys and I³-TiAl intermetallics, with a view to rendering them resistant to high-temperature environmental oxidation and oxygen embrittlement.The first part of the talk covers the surface modification of Ti and low-Al-content Ti-base alloys by using combined techniques involving either aluminization followed by plasma immersion ion implantation (PIII) of fluorine or formation of a surface barrier coating by magnetron sputter co-deposition of Ti and Al followed by vacuum annealing and PIII of F. The second part focuses on the direct surface treatment of I³-TiAl by PIII of F. Such type of fluorination enables the F-implanted alloy surface to develop a stable, adherent and highly protective alumina scale upon subsequent oxidation in air at temperatures in excess of 1000A^oC for extended exposure times. The last part deals with the fabrication of protective TiAl coatings using a two-step coating scheme. First, an Al-rich TiAl layer is formed on the I³-TiAl alloy by either MO-CVD, PVD or thermal spraying. Then the TiAl layer is treated by PIII of F. The resulting coatings are tested for oxidation resistance, oxygen embrittlement, and retention of mechanical properties. A combination of an Al-rich CVD coating and treatment by PIII of F gives the best results. An example is also given of a thermal barrier coating whose structure comprises, instead of a bond coat, a thin alumina layer formed by PIII of F and subsequent high-T oxidation. The results of these studies have been helpful in understanding the oxidation behavior of the surface-engineered alloys from both a scientific and a technological standpoint.

Heat storage has become a very important topic because of the renewable and alternative energy requests. Its availability and peak demand issues require more efficient and economic solutions for thermal energy storage at times when energy is not needed.Phase Change Materials (PCMs) use the latent heat at the solid-liquid phase transition point for storing thermal energy. PCMs are commonly grouped in organic (e.g. Paraffin waxes) and inorganic compounds (e.g. Salt hydrates). Inorganic salt hydrate PCMs exhibit a number of advantages in comparison to organic PCMs (e.g. Lower price, higher latent heat per unit volume, higher thermal conductivity). However, one of the main issues of inorganic PCMs is their insufficient long-term stability because they are corrosive to most common metals like aluminium, copper, brass, carbon steel.Heat exchanger tubes are therefore often made of stainless steel. In this work we investigated the corrosion protection of several thermal sprayed coatings on carbon steel substrate. Thermal spraying is straight forward, fast, low-cost and easy to scale-up coating technique where almost all materials can be coated on almost every substrate materials.In this work, the performance of several metal-based thermal sprayed coatings has been investigated and compared to bulk material properties of common heat exchanger materials. The immersion corrosion tests have been performed in presence of two inorganic salt hydrates, namely sodium acetate trihydrate and calcium chloride hexahydrate. The tests presented and evaluated were short-time tests (max. 6 weeks). It was concluded that coatings offer an interesting and suitable alternative to protect heat exchanger materials for heat storage applications.

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