Πλοήγηση ανά Συγγραφέα "Tsipas, D. N."
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Τεκμήριο Deposition of coatings containing Si and B on steels in a CVD fluidised bed reactor(2005-01) Agrianidis, P.; Anthymidis, K. G.; David, K.; Tsipas, D. N.Diffusion coatings are frequently used to protect materials in various aggressive environments and in order to improve their surface properties. Fluidized bed technology (FBT) has been successfully used for the deposition of different types of diffusion coatings by a C.V.D. process, e.g. aluminizing, chromizing, nitriding, carburizing. On the other hand, very little information exists on boronizing or siliconizing using FBT, although the method is simple, efficient and environmentally friendly and the boride coatings have been reported to have an excellent combination of properties, e.g. high fatigue strength and wear resistance and the silicide coatings are well known for their excellent corrosion resistance. In this paper the results of a process of boronizing and siliconizing of steels via C.V.D. in a fluidised bed reactor are presented. Coatings of different thicknesses were obtained at temperatures below 1000°C. The coatings were analysed by means of optical microscopy, as well as by x-ray diffraction (XRD) and Vickers microhardness, in terms of the coating’s composition, morphology, thickness, hardness and phase formation. The boride coatings showed significantly improved tribological properties under dry wear conditions.Τεκμήριο Evaluation of the fatigue behavior of Aluminide Coating Steel Substrate Compounds by means of the Impact Testing Method(2011-03) Anthymidis, K. G.; David, C.; Tsipas, D. N.The impact testing is an efficient experimental method that enables the quantitative and qualitative evaluation of the fatigue resistance of mono- and multilayer coatings deposited on various substrates, which was not possible with the common testing methods previously available. In this article the experimental assessment of the fatigue resistance of aluminide slurry coatings working under cyclic loading conditions by means of the dynamic impact testing method is presented. The fatigue failure mode, such cohesive or adhesive, of the investigated coatings is determined using scanning electron and optical microscopy, as well as Energy Dispersive X-ray (EDX) analysis. Critical values of impact load responsible for distinctive fatigue failure modes of the coating substrate system are obtained.Τεκμήριο Evaluation of the Fatigue Resistance of Chromium Slurry Coating Steel Substrate Compounds by Means of an Improved Impact Testing Procedure(2012) Anthymidis, K. G.; David, K.; Trakali, A.; Tsipas, D. N.Chromium coatings have been used for the protection of gas turbine blades in power plants during the last years due to their very good resistance against steam corrosion. Microhardness, scratch, adhesion and pin-on-disk sliding tests are commonly used for rapid evaluation of the mechanical properties of these coatings [1,2]. However, very limited information exists on their fatigue resistance. In this paper we present the experimental results of the impact testing examination of the above coatings. This experimental method is capable to assess the fatigue and the impact wear resistance of coatings working under cyclic impact loading conditions. From the experimental results it was concluded that the slurry Cr, Zr coatings deposited on P91 steel showed adequate fatigue strength for the above-mentioned kind of use.Τεκμήριο Fatigue resistance assessment of slurry coating steel substrate compounds under cyclic loading(2008-07) Anthymidis, K. G.; David, K.; Tsipas, D. N.Slurry coatings have been used for the protection of gas turbine materials in power plants during the last years. These coatings can be applied by spaying, brushing or dipping. The main constituent elements are silicon, chromium, potassium, borium, carbon and zirconium. They are characterized by high hardness and very good resistance against corrosion, erosion, abrasive and adhesive wear. To guarantee the reliability of coated steam turbines components used in power plants, the lifetime assessment of the coatings and their failure prediction become very important. Microhardness, scratch, adhesion and pin-on-disk sliding tests are commonly used for rapid evaluation of the mechanical properties of these coatings [F. Loeffler: Thin Solid Films, Vol. 339 (1999), p. 181]. However, the above testing methods do not model the dynamic cyclic fatigue. In this paper we evaluate the fatigue resistance of slurry coatings working under cyclic loading conditions by the impact testing method. The coating failure mode and its extent were assessed by SEM observations and EDX analysis. From the experimental results it was concluded that the Si,Cr,O,B,C coatings deposited on P91 steel substrate showed an improved fatigue strength compared to that of Si,Cr,O deposited on the same substrate.Τεκμήριο Siliconizing in a Fluidized Bed Reactor(2013-11) Anthymidis, Konstantinos; David, K.; Trakali, Afroditi; Tsipas, D. N.Fluidized bed technology has been used for surface engineering applications in the deposition of hard and/or corrosion resistant layers e.g. aluminizing, chromizing, nitriding, carburizing, boronizing. In the present paper we used fluidized bed technology (FBT) to deposit silicide coatings on steels. The silicide coatings are well known for their excellent corrosion resistance. Siliconizing in fluidized bed is a promising method to improve the corrosion resistance of steel without altering its other properties. The asproduced silicide coatings are uniform all over the steel substrate, with good thickness, adequate adherence and consisted only from the phase FeSiC.