2008 fascicula9 nr2

Electrodeposition Obtaining and Corrosion Behaviour of Phenol Formaldehyde Resin/Zinc Composite Coatings

2020-09-03T13:24:29Z

Electrodeposition Obtaining and Corrosion Behaviour of Phenol Formaldehyde Resin/Zinc Composite Coatings Mitoșeriu, Olga; Ciubotariu, Alina; Benea, Lidia; Ponthiaux, Pierre; Wenger, Francois The present work has the purpose of obtaining composite coatings in zinc matrix by using phenol - formaldehyde resin type NOVOLAC (RESITAL 6358/1) in the electrodeposition process of zinc. The PF resin/Zn composite coatings were electrodeposited from a suspension of PF resin particles (diameter < 56 μm) in aqueous zinc sulphate electrolyte. Suspension was prepared by adding 10g/L and 25g/L PF resin particles into solution. The pure zinc coating has a rather regular surface, whereas the composite coatings surface has fine surface structure. For layers obtained at 3A/dm2 the polarization resistance is higher for composite coatings with 10 g/L PF resin (Rp = 238.75 Ω cm2) than pure zinc (Rp = 34.54 Ω cm2). For layers obtained at 5A/dm2 the polarization resistance is higher for composite coatings with 25 g/L PF resin (Rp = 430.19 Ω cm2) than pure zinc (Rp = 127.34Ω cm2). As test solution 0.5M sodium chloride was used, it was observed that by adding PF resin particles in zinc electrolyte for electrodeposition it was obtained a very good distribution of resin particles on zinc surface and PF resin/Zn composite coatings obtained are most resistant at corrosive attack than pure zinc obtained from electrodeposition under the same conditions. THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. FASCICLE IX. METALLURGY AND MATERIALS SCIENCE N0. 2 – 2008, ISSN 1453 – 083X

Laser Surface Alloying of Some Steels from SiC Predeposited Powders

2020-09-03T13:24:29Z

Laser Surface Alloying of Some Steels from SiC Predeposited Powders Levcovici, S.M.; Levcovici, D.T. For the purpose of studying the possibilities of increasing the wear resistance, specimens of three steels with 0.2%C, 0.46%C and 1%C were surface alloyed with reinforcement from overlapping pastes with green SiC hard particles with the granulation 800 and 320. The melting of surface layer was performed by CO2 continous wave laser on a numerical x-y table. On these specimens the micro structural characteristics, geometry of molten zone, micro hardness variation in the alloyed layer depth and the HV5 hardness on a laser processed surface were determined, which allowed defining the added material with the best hardening effect. The conditions to obtain compact surface layers with 2-3 time higher hardness than the base material were determined. THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. FASCICLE IX. METALLURGY AND MATERIALS SCIENCE N0. 2 – 2008, ISSN 1453 – 083X

The Modern State of Works in Field of Electron-Beam Technology of Melting and Evaporation of Metals and Non-Metals in a Vacuum

2020-09-03T13:24:29Z

The Modern State of Works in Field of Electron-Beam Technology of Melting and Evaporation of Metals and Non-Metals in a Vacuum Grechanyuk, I.N.; Grechanyuk, N.I.; Croitoru, G. In developing of new processes for growing metal (composite) films, the main attention is given to controlling the metal vapour flows: through energy state of the condensing particles, their molecular composition, intensity, spatial distribution of the flow, etc. It is known that the widely accepted open-type evaporators, including quasi-closed ones, are characterized by instability of the directivity diagram of the vapour flow in time, even at constant temperature. Radiation load on the film growth surface from these sources is sometimes comparable to the energy of vapour flow condensation. Therefore, when they are used, it is quite difficult to produce reproducible film structures with controllable parameters. Particular difficulties arise at high evaporation rates, when micro-drops are usually present in the vapour flow THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. FASCICLE IX. METALLURGY AND MATERIALS SCIENCE N0. 2 – 2008, ISSN 1453 – 083X

Structure Effects Over Behavior of Graphite Gray Iron in Running

2020-09-03T13:24:29Z

Structure Effects Over Behavior of Graphite Gray Iron in Running Preda, Adriana; Rîpă, Minodora; Miculescu, Florin; Dulea, Gabriela The work aims at emphasizing the structure changes of graphite gray iron, as a result of make-casting conditions and their effects over behavior in running of several cast items. Researches consisted of complex characterization of several gray iron specimens sampled from damaged items comparatively to other suitable ones. Chemical composition, crack aspect, tensile strength, structure, kind, micro hardness of structural constituent were analyzed. Laboratory researches made by optical and electronic microscopy emphasized the showing up of some unsuitable structures with fragile structural constituents and areas unpurified by exogenous inclusions as well as degenerated graphite. All of these steady structural changes had a powerful fragility effect over the material. This fact was confirmed by mechanical characteristics and analysis of cracking area. Results corroborating allowed finding the causes of graphite gray iron cast items damage as a result of a faulty make-casting technological management and incomplete heating treatment. THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. FASCICLE IX. METALLURGY AND MATERIALS SCIENCE N0. 2 – 2008, ISSN 1453 – 083X