Metalinių purkštųjų dangų struktūros ir savybių priklausomybės nuo technologinių parametrų tyrimas ; Research of dependence of structure and properties of thermal sprayed metallic coatings upon technological parameters

Vytautas Bučinskas

Description

Irmantas GEDZEVI ČIUS RESEARCH OF DEPENDENCE OF STRUCTURE AND PROPERTIES OF THERMAL SPRAYED METALLIC COATINGS UPON TECHNOLOGICAL PARAMETERS Summary of Doctoral Dissertation Technological Sciences, Materials Engineering (08T) 1137 Vilnius „Technika“ 2005 VILNIUS GEDIMINAS TECHNICAL UNIVERSITY Irmantas GEDZEVI ČIUS RESEARCH OF DEPENDENCE OF STRUCTURE AND PROPERTIES OF THERMAL SPRAYED METALLIC COATINGS UPON TECHNOLOGICAL PARAMETERS Summary of Doctoral Dissertation Technological Sciences, Materials Engineering (08T) Vilnius „Technika“ 2005 Doctoral dissertation was prepared at Vilnius Gediminas Technical University in 2000 – 2005. The dissertation is being defended as an external work.

Sujets

• Materials science

Informations

• Publié par: vilnius_gediminas_technical_university
• Publié le: 01 janvier 2005
• Nombre de lectures: 20

Extrait

 

 

    Irmantas GEDZEVIČIUS         RESEARCH OF DEPENDENCE OF STRUCTURE AND PROPERTIES OF THERMAL SPRAYED METALLIC COATINGS UPON TECHNOLOGICAL PARAMETERS           Summary of Doctoral Dissertation Technological Sciences, Materials Engineering (08T)               Vilnius Technika 2005

 

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VILNIUS GEDIMINAS TECHNICAL UNIVERSITY                   Irmantas GEDZEVIČIUS       RESEARCH OF DEPENDENCE OF STRUCTURE AND PROPERTIES OF THERMAL SPRAYED METALLIC COATINGS UPON TECHNOLOGICAL PARAMETERS       Summary of Doctoral Dissertation Technological Sciences, Materials Engineering (08T)                 Vilnius Technika 2005

 

 

 

Doctoral dissertation was prepared at Vilnius Gediminas Technical University in 2000  2005. The dissertation is being defended as an external work. Scientific Supervisor Prof Dr Habil Algirdas Vaclovas Valiulis(Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering  08T)   The Dissertation is being defended at the Council of Scientific Field of Materials Engineering at Vilnius Gediminas Technical University: Chairman Prof Dr Habil Antanas Laukaitis(Institute of Thermal Insulation of Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering  08T)   Members: Dr Habil Eugenijus atkovskis Gediminas Technical (Vilnius University, Technological Sciences, Materials Engineering  08T)   Assoc prof Dr Bonifacas Vengalis Physics Institute, (Semiconductor Technological Sciences, Materials Engineering  08T) Dr   Ina Pundienė (Institute of Thermal Insulation of Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering  08T) Dr Rimantas Levinskas(Lithuanian Energy Institute, Technological Sciences, Materials Engineering  08T)   Opponents: Prof Dr Habil Sigitas Tamulevičius(Kaunas University of Technology, Technological Sciences, Materials Engineering  08T) Assoc prof Dr Jadvyga Regina Kerienė Gediminas Technical (Vilnius University, Technological Sciences, Materials Engineering  08T)   The dissertation will be defended at the public meeting of the Council of Scientific Field of Materials Engineering in the Senate Hall of Vilnius Gediminas Technical University at 2 p. m. on July 04, 2005. Address: Saulėtekio al. 11, LT-10223 Vilnius-40, Lithuania Tel.: [phone]; fax [phone], e-mail [e-mail] The summary of the doctoral dissertation was   distributed on June 03, 2005 A copy of the doctoral dissertation is available for review at the Library of Vilnius Gediminas Technical University (Saulėtekio al. 14, Vilnius, Lithuania)   © Irmantas Gedzevičius, 2005

 

 

 

VILNIAUS GEDIMINO TECHNIKOS UNIVERSITETAS               Irmantas GEDZEVIČIUS       METALINIŲPURKTŲJŲDANGŲ   STRUKTŪROS IR SAVYBIŲPRIKLAUSOMYBĖS NUO TECHNOLOGINIŲPARAMETRŲ   TYRIMAS           Daktaro disertacijos santrauka Technologijos mokslai, mediagųininerija (08T)                 Vilnius Technika 2005  

 

 

 

Disertacija   rengta   2000      2005   metais   Vilniaus Gedimino technikos universitete.   Disertacija ginama eksternu. Mokslinis konsultantas prof. habil. dr. Algirdas Vaclovas Valiulis (Vilniaus Gedimino technikos universitetas, technologijos mokslai, mediagų ininerija  08T). Disertacija ginama Vilniaus Gedimino technikos universiteto Mediagų   ininerijos mokslo krypties taryboje: Pirmininkas prof. habil. dr. Antanas Laukaitis Gedimino technikos (Vilniaus universiteto Termoizoliacijos institutas, technologijos mokslai, mediagų   ininerija  08T). Nariai: habil. dr. Eugenijus atkovskis (Vilniaus Gedimino technikos universitetas, technologijos mokslai, mediagųininerija  08T), doc. dr. Bonifacas Vengalis (Puslaidininkių institutas, fizikos technologijos mokslai, mediagųininerija  08T),    dr. Ina Pundienė Gedimino technikos universitetas, (Vilniaus technologijos mokslai, mediagųininerija  08T), dr. Rimantas Levinskas energetikos institutas, technologijos (Lietuvos mokslai, mediagųininerija  08T). Oponentai: prof. habil. dr. Sigitas Tamulevičius(Kauno technologijos universitetas, technologijos mokslai, mediagųininerija  08T), doc. dr. Jadvyga Regina Kerienė Gedimino technikos (Vilniaus universitetas, technologijos mokslai, mediagųininerija  08T).   Disertacija bus ginama vieame Mediagų ininerijos mokslo krypties tarybos posėd. 14 val. Vilniaus Gedimino technikos universitetodyje 2005 m. liepos 4 senato posėdiųsalėje. Adresas: Saulėtekio al. 11, LT-10223 Vilnius-40, Lietuva. Tel.: [phone]; faksas [phone], el. patas [e-mail] Disertacijos santrauka isiuntinėta 2005 m. birelio 3 d. Disertaciją peri galimaūrėti Vilniaus Gedimino technikos universiteto bibliotekoje (Saulėtekio al. 14, Vilnius, Lietuva) VGTU leidyklos Technika 1137 mokslo literatūros knyga   © Irmantas Gedzevičius, 2005

 

 

 

GENERAL CHARACTERISTIC OF THE DISSERTATION   Aim of the work    •   the method of final elements to design the arc spraying process. ToUsing determinate influence of nozzle configuration for spraying particles velocity, jet configuration and to find the shape of optimal inner nozzle orifice. •   determine in spraying jet flying drops of liquid metal velocity,To temperature, diameter and influence of these factors for coatings formation and their exploitations properties. •   To spray the coatings using arc spraying equipment and modified noozle obtained with numerical calculation and investigate the coatings properties, to determine the spraying matherials type, technological arc spraying parameters influence on coatings mechanical and physical properties and also to verify the theoretical postulates of research work. •   To relate technological arc spraying dependences obtained in this research with concrete technological process and suggest the recommendations for thermal spraying.     Methodology of research.The theoretical and experimental investigations have been presented in this work. The Computational Fluid Dynamic (CFD) code PHOENICS was used for numerical calculation. The particles size was calibrated with LASER granulometer Coulter LS230. The sprayed particles velocity, temperature and diameter were measured by the diagnostic system DVP-2000. Coating adhesion was measured in accordance with the ASTM C 633-79 standard pull-off tensile test. Collected particles and coatings microstructures were analysed with optical microscope Nicon Epiphot® with digital camera Nicon Coolpix E995 and scanning electron microscope Amray 1000A. The pores, oxides contents and porosity of sprayed coatings were determined in a digital metallographic method using the software Scion Image. The coatings hardness and modulus of elasticity was investigated using the Knoop indentation test and machine to force Clemex MT-2001. The coatings surfaces roughness (Ra and Rz) was measured with equipment Taylor-Hobson Surtronic 3P.   Scientific novelty   •   the basis of final elements method, by the help of theCreated algorithm on Computational Fluid Dynamic (CFD) code allow to make prognosis of arc

 

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spraying jet parameters dependents from the inner nozzle orifice configuration.   •   Using unique, especially sensitive, on-line process registered systems, determinated spraying materials (small drops) geometry, distribution, velocity, temperature and found this parameters coherence with spraying coatings properties (morphology, adhesion, texture, oxides contents, hardness, elastic modulus). •   The geometrical parameters of arc spraying noozle were optimised not by experimental way, but with numerical calculation, with allow more versatile, quicker, precisely and cheaper evaluate the physical, thermodynamic and nozzle orifice parameters.   Practical value.algorithm of arc spraying process simulation was  The created, which allow to make prognosis of arc spraying jet configuration and flying particles parameters. This scientific research shows the dependence between the arc spraying technological parameters and mechanical and physical properties of the obtained coatings. It was established, how by change of the spraying parameters the coatings with the best exploiting parameters can by received. The performed research shows the influence of the kind of the sprayed material on morphology of the formed jet particles and on technical and structural characteristics of the formed coatings. On basis of obtained results made suggestions how to improve the creation of thermal spraying coatings making new products or making restoration.   Defended propositions By help of the finited elements method the geometric parameters of the spraying equipment elements (nozzle) can by simulated and characteristics of the spraying jet can by predicted. The arc spraying gun inner nozzle orifice geometry influence the spraying jet configuration, temperatures field and the gas velocity field distribution. The thermal spraying coatings structure, physical and mechanics properties (adhesion, pores, oxides contents, hardness, elastic modulus, roughness and etc.) decide the characteristics in jet flying particles (velocity, size, flight duration in gas jet, temperature).   The scope of the scientific work. The scientific work consists of the general characteristic of the dissertation, 5 chapters, conclusions, list of literature, list of publications and addenda. The total scope of the dissertation  119 pages, 84 pictures, 21 tables and 2 addenda.

 

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Approval of the work    1.   International conferenceInternational Thermal Spray Conference 2003 (ITSC-2003), Orlando, USA. 2.   12 th International scientific conferenceAchievements in Mechanical & Materials Engineering   (AMME 2003), Gliwice-Zakopane. 3.   Republican conferenceMediagų ininerija  2003   (Materials Engineering  2003), Kaunas, KTU. 4.   International conference   тсорнееиаМишон-2003(Machines Building -    2003), Minsk. 5.   International conference   нишартсоМоение-2004(Machines Building - 2004), Minsk. 6.   International conferenceMechanics 2003, Kaunas, KTU. 7.   International conferenceНаучно-технические   проблемы   прогнозирования   надежности   и   вочеодглионтс   конструкций   и   методы   их   решения(Scientific and technical problems of reliability and durability prognosis of mechanical constructions and ways of their solution),2003,Saint Petersburg.     STRUCTURE OF THE WORK   The first chaptergivesa review of literatureon thermal spray metods, the technological coatings properties of thermal spraying coatings. The chapter focuses initially on various wear modes that effect engineering surfaces in service and how coatings protect these surfaces. Various thermal spraying techniques are examined, in terms of their function and performance with reference to internationally published research. The effect of thermal spraying parameters on the coatings performance is investigated in terms of microstructure and mechanical properties. The second chapterpresents   the methodology of analytical and experimental researches. The software PHOENICS was chosen for numerical calculation of arc spraying jet. Developed by Company SHAM, PHOENICS is a general programme of mechanics of the fluids intended for the simulation of all types of flows and heat exchange. In the experimental researches the particles size was measured with LASER granulometer Coulter LS230. The LS230 particle size analyser is designed to measure particles from 0.04μm to 2000μm on powders suspended in appropriate liquid. The LS230 is equipped with both a diffraction sample cell and a PIDS (polarization differential scattering) sample cell.

 

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The sprayed particles velocity, temperature and diameter were measured by the diagnostic system DVP-2000 (Fig 1). The complete monitoring system consists of three main components: a) the sensor head located near the arc spray torch collecting the thermal radiation from the hot sprayed particles, b) the detection module containing the optical components and photo detectors, and c) an IBM-compatible personal computer (control module) equipped with the required digitizing and computing boards.  

  Fig 1.DPV-2000 operation principle   The sensor head is located near the arc spray gun collecting thermal radiation emitted by the hot in-flight particles. The collected light is transmitted to the detection module through an optical fiber bundle. The light emitted by a hot particle traveling near the focal plane of the collection optics is collected twice as the particle moves across the two slits. The distance between the slits images being known, the velocity of the particle can be computed from its transit time. The particle temperature is determined by measuring the thermal radiation intensity at two different wavelengths. For investigations of sprayed particles and the polished cross section of the spray deposit the scanning electron microscope Amray 1000A are used. Coating adhesion was measured in accordance with the ASTM C 633-79 standard pull-off tensile test. This is a common method of characterizing the comparable bond strength of thermally sprayed coatings. The results of the tests determine the degree of adhesion of a coating to a substrate in tension normal to the surface. 25 mm diameter coupon was stuck onto two sample holders for

 

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testing. The latter ones were set into a tensile machine. A progressive force at a constant speed of 0.075 cm/min was applied to set up until the spallation occurred.   Polished cross section of the spray deposit was digitised by using a Nikon EPIPHOT ®   optical microscope with a Nikon Coolpix E955 digital camera. Computer image analysis program Scion Image ® based on the image processing toolbox was used to analyse the true-colour image. Instead of using grey level as threshold, the RGB value of the pixels was utilised as criterion to distinguish the different features of the coating microstructure. In this way, the area fraction and distribution of oxide and porosity can by defined with high accuracy. The coatings hardness are measured using a calibrated machine to force Clemex MT-2001 a diamond indenter of specific geometry, under a test load 200 g, into the surface of the test cross section coating and to measure the diagonals (ASTM E 384-84). Surface roughness depth - Ra and mean roughness depth  Rz, (ISO 1302 : 1994) were measured witch profilometer Taylor-Hobson Surtronic 3P. The third chapter the investigations of computational modeling presents of the arc spraying gun nozzles configurations.   The standard gun exit is composed of a converging nozzle exhibiting a 6 mm exit diameter. The meeting point of the wires (where the electric arc is formed) is situated just at the centre of the exit area. The changes that were made on nozzle geometry and were tested included additional extension of the standard nozzle (Fig 2). This approach was expected to lead to the first tendency (qualitative comparison) of the effect of these small changes. Many models of nozzles were tested (nozzle of Laval, nozzles with divergences or convergences). The flows of the six new nozzle configurations were modelled. The influence of transporting gas (air) speed, configuration of jet, temperature gradients in jet, enthalpy were calculated. All the results of modelling were compared with the process parameters of standard nozzle. Figure 2 presents a view of these different nozzle exit designs. In each case, the results were compared to those obtained for the standard geometry (Figure 2-a). More precisely, criteria such as - the velocity magnitude and the jet divergence in the near exit region were retained. Figure 2-b incorporates a progressive change in the converging angle. Figures 2-c to 2-e show different lengths of constant area nozzle extensions whereas geometries on Figures 2-f and 2-g were built up with a slightly diverging extension. For the same heating power, the calculated model of the jet temperature fields showed that temperature of jet flowing from standard nozzle is higher than jet temperature flowing from the modified nozzle. The rate of the flow of air is bigger from the modified nozzle. The speed vectors (Fig 3) shows that the

 

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divergence of the jet of the modified nozzle is smaller, than for the jet of the standard nozzle, but the size of the speed vector in the area adjacent to electric arc is larger. This indication enables us to suppose, that the spray of the modified nozzle accelerate particles. The calculations allowed estimate air blow velocity in Y-Z directions (Fig 4). For the modified nozzle the blow speed on the directionZhigher and is smaller in the directionis Y.  

 

 

Fig 2.View of the tested nozzles

 

  Fig 3.Vectors of the speed for the standard (over centre line) and modified designs (down centre line)

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