Wyniki 1-10 spośród 13 dla zapytania: authorDesc:"WALDEMAR WOŁCZYŃSKI"

Pattern selection within the stripes strengthening the hexagonal (Zn)-single crystal

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A phenomenon of strengthening is observed for the hexagonal (Zn)-single crystal equipped with regular stripes which contain the Zn16Ti intermetallic compound. It is well known that the strengthening by the addition of some particles or elements is available [1, 2]. Usually, the strengthening leads to significant increasing of some mechanical properties of a given single crystal. The studied hexagonal (Zn)-single crystal was doped by the small amount of titanium and copper. The addition of copper modifies the specific surface free energy at the solid/liquid interface. Copper does not form an intermetallic compound with the zinc but is localized in the zinc/titanium solid solution, (Zn). However, titanium forms an intermetallic compound with the zinc, Zn16Ti. The (Zn)-Zn16Ti system is the pseudobinary eutectic system. It gives an opportunity to control the growth of the Zn hexagonal single crystal, and first of all to control the thickness of the stripes which appear cyclically within the single crystal (Fig. 1). Moreover, the imposed changes of the growth rate select the pattern within stripes strengthening the (Zn)-single crystal. Therefore, two threshold growth rate were recorded: v1 - at which L-shape rod like structure (irregular eutectic structure) transforms into lamellar structure (regular eutectic structure), v2 - at which lamellar structure transforms into rod-like structure (regular eutectic structure). Some transformations from rod-like into lamellar structure are known, especially in the Al-Si and Fe-C eutectic systems [3÷9]. Analogously to the Al-Si and Fe-C eutectic the Zn-Zn16Ti eutectic also evinces irregular structure but[...]

Coating Zn formation during hot dip galvanizing

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The studies aimed at an analysis of the formation and growth kinetics of zinc coating on reactive silicon-killed steels in a zinc bath. The growth kinetics of the produced zinc coatings was evaluated basing on the power-law growth equation. As regards galvanizing of the surface of products, investigation was done for various steel grades and ductile iron taking into account the quality and th[...]

Morfologia struktury obrabianej cieplnie powłoki Al2O3-SiO2 natryskiwanej plazmowo na podłoże metaliczne

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Analizowano wyniki badań struktury powłoki o składzie Al2O3 + 30% mas. SiO2 natryskiwanej plazmowo na podłoże ze stali stopowej. Zastosowano wyżarzanie złącza w temperaturze 1150°C przez 50 godzin. Stwierdzono, iż na całej grubości powłoki do 200 µm występuje mulit oraz korund. Efektem wyżarzania jest powstawanie małych ziaren, w pasmach. W pobliżu podłoża występują fazy drobnokrystalic[...]

The zinc coating solidification on surface silicon steels and DI castings

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Hot dip galvanizing of reactive steels with high silicon content is a very interesting problem still lacking a complete and practically acceptable solution, although the currently used practice of steel making forces in a way the use of high silicon levels. An important issue in hot dip galvanizing is the phenomenon of the formation of a thick, brittle and dull-grey coating when the content of silicon (and phosphorus) in steel exceeds the critical but quite commonly used level, expressed by equation (1): (Si + 2.5P)·103 = ESi,P (1) Below this value, the obtained coating is characterized by a correct glossy finish and ,,normal" thickness, while above the critical level of silicon and phosphorus equivalent the coating loses its adhesive force and as such can have poor adhesion, which means that the zinc volume necessary to produce the finally required coating thickness may be too large and therefore too expensive. As follows from the studies described in [1÷4], the chief solution to the problem of a wide range of the silicon and phosphorus equivalent values in steels (so more in cast iron) available at present in the domestic market seems to be a conformity certificate specifying precisely the composition of the steel used for elements which are to be subjected to the galvanizing treatment or proper selection of steel already at the stage of designing or making these elements (as far as it is possible). Procedure of this type should be effectively implemented in the galvanizing plants which use a wide spectrum of different steel grades, while the plants which make on request galvanizing of single elements should try to optimize the composition of the zinc bath they commonly use. Recently, some novel solutions have been offered in the field of hot dip galvanizing. One of them, widely used by industry, is the process of zinc-nickel galvanizing [5÷8]. The process of hot-dip galvanizing in Zn-Ni bath is at present considered to[...]

Mechanism of Solidifi cation under Meta-Stable Condition for Fe-Al Particle Sprayed by the Detonation Method

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Particles of the Fe-Al type (less than 50 μm in diameter) were sprayed onto 045 steel substrate by means of the detonation method. The particles contained 15, 49 and 63 at.% Al, respectively. A single particle containing 63 at.% Al was subjected to the detailed analysis. The TEM and SAED techniques revealed in the sprayed particle three sub-layers of: an amorphous phase A f , periodically situated lamellae of the FeAl + Fe2Al5 phases, and a nonequilibrium phase N f . As a result of the spraying a solid / liquid system was formed: substrate / melted particle part / non-melted particle part. A hypothesis dealing with the solidifi cation mechanism of such a single particle (partially melted) and with nominal composition N0 = 0.63 (63 at.% Al) is presented. The solidifi cation mechanism is referred to the Fe-Al meta-stable phase diagram shown schematically. A melted part of particle solidifi ed rapidly according to the phase diagram of meta-stable equilibrium and at a signifi cant deviation from the thermodynamic equilibrium. The solidifi cation occurred simultaneously in two directions: towards a substrate and towards an air. Keywords: Fe-Al coating, D-gun spraying, meta-stable solidifi cation, steel substrate ochrona przed korozja 11/2010 s. 520-523 Ochrona przed Korozją, vol. 53, nr 11 521 1. Introduction The DGS, HVOF and plasma spraying techniques applied to the production of coatings from powders offer practically unlimited abilities in establishing composition of a coating. A control of the spraying parameters with the objective to obtain coatings with unique exploiting properties like resistance to abrasive wear, erosion, corrosion, high temperature corrosion or thermal shocks, as well as good adhesion and low porosity was the subject of number of works, [1-17]. According to some considerations [7, 18- -22] a temperature of particles during their deposition does no exceed the melting point of a particle material. Howev[...]

Solidification of Fe-Zn sublayers during galvanizing process

  Studies on the technology of producing hot-dip coatings can be considered fully successful when a mechanism responsible for the growth of these coatings is fully clarified. The research conducted for many years [1÷13] have proved that hot-dip coatings are composed of two main layers. The first layer directly contacting the substrate is an alloyed layer, usually composed of a few sublayers of the intermetallic phases. The second layer - the external layer - is solidifying on the surface of an alloyed layer when the galvanized product emerges from bath and is being cooled [3, 4]. It shows beyond doubt that in every case an analysis of the zinc coating structure should be based on the equilibrium diagram of Fe-Zn alloys, what is shown in Figure 1 and has been the subject of numerous investigations [10÷13]. The broken line in Figure 1 denotes the process temperature TR of the zinc bath used for hotdip galvanizing. The value of this temperature is used to estimate the required degree of undercooling[...]

Reactions at a Solid / Liquid Interface during Formation of the Intermetallic Multi-layer

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A reactive diffusion is postulated to be observed during formation of the intermetallic multi-layer on a given substrate. Particularly, back-diffusion is envisaged according to a model for the solute redistribution. Finally, formation of the intermetallic multi-layer results from peritectic reactions as assumed in the model. Thus, formation of the Al3Ni2 - Al3Ni intermetallic multi-layer on t[...]

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