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Krella A.,Szewalski Institute of Fluid Flow Machinery
Wear | Year: 2013

TiN and CrN coatings with various thicknesses deposited on X6CrNiTi18-10 and X39Cr13 steel by means of the cathodic arc evaporation method were tested in a cavitation tunnel with a slot cavitator and tap water as the medium. Steels were subjected to thermal treatment in order to obtain substrates of different properties. Present investigation shows that the properties of the substrate, especially the thermal properties, influence the properties of the TiN coatings. Deposition of hard TiN and CrN coatings on the steel substrates has caused the improvement of the cavitation erosion resistance. The increase of coating thickness decreases the positive effect of the TiN and CrN coatings deposition. The 8 and 12μm thick TiN and CrN coatings undergo degradation mostly via spalling by removal of the thin flakes of the coating. The resistance parameter, RCAV=(kc/ks)/(αc/αs){dot operator}(Hc{dot operator}(1-vc2))/(Ec{dot operator}(1+vc2)){dot operator}(Es{dot operator}(1+vS2))/(Hs{dot operator}(1-vS2)){dot operator}(LC2/pc{dot operator}h), where k is thermal conductivity, α is the thermal expansion coefficient, H is the hardness in GPa, LC2 is the adhesion force in N obtained in the scratch tests, E is the Young's modulus in GPa, pc is the number of phases in the coating phase composition, h is the coating thickness in μm, subscript c applies for coating, s is for the substrate, has been positively verified by present investigations. This indicates that not only the mechanical properties of the coating and of the substrate influence the cavitation erosion resistance of the PVD coating-steel substrate system, but also their thermal properties. © 2012 Elsevier B.V.

Krella A.,Szewalski Institute of Fluid Flow Machinery
Wear | Year: 2011

A series of cavitation erosion tests were carried out to investigate the resistance of the TiN coatings against cavitation action. The TiN coatings were deposited at various deposition parameters on austenitic stainless steel, X6CrNiTi18-10, with various coating thicknesses by means of the cathodic arc evaporation method (CAVD). Investigations were performed in a cavitation tunnel with a slot cavitator. The estimation of cavitation resistance of the TiN coatings was performed on the basis of the incubation period and the mass loss. The investigations show that coating hardness, Young's modulus, adhesion and coating thickness have an influence on coating endurance to cavitation degradation. The parameter H·LC2/E·h1/2 shows very good fitting to data points (R2=0.9707). Along with the increase of the H·LC2/E·h1/2 parameter the mass loss decreases indicating a continuous improvement in the cavitation erosion resistance. © 2010 Elsevier B.V.

Krella A.K.,Szewalski Institute of Fluid Flow Machinery
Engineering Failure Analysis | Year: 2011

Most machinery elements are coated with hard coatings to prolong their lifetime and to improve working efficiency. Cavitation test was used as a tool for studies of dynamic impact degradation. Ti- and Cr-based coatings were chosen for investigations. The TiN and Cr-N coatings with various thicknesses were deposited on stainless steel by means of the cathodic arc evaporation method at various deposition parameters. Tests were performed in the cavitation chamber with a system of barricades. Nearly all the TiN and Cr-N coatings have undergone micro-undulation. The first cohesive fractures have occurred on top of the micro-folding and at delamination spots. The analysis of degradation mechanism of thin hard coatings under repeated impact loading has resulted in deriving a new empirical parameter suitable for description of the hard coating cavitation resistance. The derived parameter is proportional to the plasticity index, H/E (defined as ratio of hardness, H, and Young's modulus, E), adhesion force, LC2, ratio of thermal conductivity of the coating to that of the substrate, and inversely proportional to the number of phases in the coating phase composition, the ratio of the thermal expansion of the coatings to that of the substrate and the square root of the coating thickness. The new endurance parameter shows good correlation with the mass loss of all the tested hard coatings indicating a continuous improvement in the erosion resistance with the increase of the new parameter. © 2010 Elsevier Ltd.

Mikielewicz D.,Technical University of Gdansk | Mikielewicz J.,Szewalski Institute of Fluid Flow Machinery
Applied Thermal Engineering | Year: 2010

A thermodynamic criterion for selection of a fluid both for subcritical and supercritical organic Rankine cycle has been proposed. Theoretical performances of few fluids have been comparatively assessed for use in low-temperature domestic organic Rankine cycle micro systems. Of the 20 fluids investigated, ethanol, R123 and R141b appear as the most suitable for small scale domestic CHP applications. © 2010 Elsevier Ltd. All rights reserved.

Kicinski J.,Szewalski Institute of Fluid Flow Machinery
Bulletin of the Polish Academy of Sciences: Technical Sciences | Year: 2013

This paper presents examples of technologies for distributed energy generation developed under the projects coordinated by the IFFM PAS in Gdańsk. These are CHP units (generating heat and electricity) for houses with a power from several to tens of kW and for municipalities in the form of the Municipal Energy Centers (with a capacity of several hundred kW up to several MW). A unique project, specializing in "energy-plus" technologies for residential houses and other buildings, which aims to build a Research Centre of PAS in Jabłonna is also presented,. These are key technologies for energy sector with respect to distributed generation. Additionally, the article discusses the conditions and opportunities for the development of energy generation or more broadly: civic energy generation in our country. Civic energy generation is a great vision in which the citizen becomes an entity and do not subject to the energy market, and additionally has its virtual advisor in the form of smart grid and data processing technologies in a "digital cloud".

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