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Theses for a scientific degree.


Rudoj Yu.E. Development of Gradient Thermal Barrier Coatings and Electron Beam Technology for Deposition thereof on Gas Turbine Blades

Thesis for scientific degree of candidate of technical sciences in speciality <<Metallurgy of high-purity metals and special alloys>>.

E.O. Paton Electric Welding Institute of the NAS of Ukraine, Kiev 2005. Date of the thesis defending is 1st of March 2006.

Conditions of deposition of the thermal barrier coating on substrate with a gradient of chemical composition and structure over its thickness with outer ceramic layer, which include electron beam heating and evaporation of a mixture of metals (alloys) and oxides (in the form of a compressed pallet, located on end of a ceramic ingot from stabilized zirconium dioxide), having different pressure of vapor at evaporation temperature, are determined.

Structure and functional properties of gradient thermal barrier coatings metal--ceramics with a transition zone on bases of the Al--Zr[O.sub.2](Y2[O.sub.3]), Al--Pt--Zr[O.sub.2](Y2[O.sub.3]) and Al--Y--Zr[O.sub.2](Y2[O.sub.3]) systems, produced by a single-stage process of application, are investigated. Possibility of regulating structure of gradient coatings by means of chemical composition change of the mixtures being evaporated is shown. Optimization of chemical composition of a pallet being evaporated allows producing a long-lasting gradient thermal barrier coating with long thermal-cycle working life in air.

Regularities of chemical composition and structure change of transitional zones metal-ceramics of deposited gradient coatings as a function of the deposition process technological parameters are studied.

The mechanism of formation of gradient structures produced by electron beam evaporation of the zirconium dioxide based composite ceramic ingot is considered. Results of investigations of chemical composition, structure and properties of recommended thermal barrier gradient coatings NiCoCrAlY + AlCr/Zr[O.sub.2](7Y2[O.sub.3]) and Me^Cy + NiAl/Zr[O.sub.2](7Y2[O.sub.3]) deposited from vapor phase on surface of high-temperature alloys are presented.

Single-stage electron beam technology based on evaporation of a composite ceramic ingot allows depositing gradient thermal barrier coatings on gas turbine blades with higher level of reliability and longer service life and at lower cost in comparison with existing multi-stage technological processes of producing thermal barrier coatings.

Teslevich S.M. New Technologies and Equipment for Producing Titanium Sponge and its Remelting into the Ingot

Thesis for scientific degree of candidate of technical sciences in speciality <<Metallurgy of high-purity metals and special alloys>>.

E.O. Paton Electric Welding Institute of the NAS of Ukraine, Kiev 2006. Date of the thesis defending is 15th of March 2006.

Issues of improving quality of spongy titanium and its remelting, as well as development of principally new installation for production of spongy titanium with cycle output 3.8 t are considered in the thesis.

Methodology of multiple increase of the reaction rate of titanium reduction from its tetrachloride by magnesium on a periodically renovated surface of Ti-containing melt is developed.

Temperature parameters for unconstrained transportation of the products of titanium reduction reaction over steam conduit from the reduction retort into the condenser-retort are determined. On the basis of a complex of heat engineering and engineering-technological investigations new technologies for reduction of titanium from titanium tetrachloride by magnesium and vacuum separation of formed in the process of the reduction reaction mass with production of spongy titanium of the highest grades have been developed for the new apparatus.

Comprehensive investigations of the technology for production of high-quality spongy titanium on laboratory and pilot installations have been carried out. Conditions of controlled removal of residual chlorine in vacuum separation of spongy titanium are determined. Experimental check of distribution of impurity elements over volume of the spongy titanium block, having mass up to 3.8 t, is carried out.

Special specimens are prepared, containing 0.08--0.45 wt.% of residual chlorine, to be subjected to remelting in induction and plasma-arc furnaces. The investigations showed that hydrogen and moisture are present in gas phase. Correlation dependence between increase of residual chlorine content in spongy titanium and amount of hydrogen in gas phase above the melt is established. It is shown that content of hydrogen in metal in induction melting exceeds the equilibrium one 1.2--1.3 times.

For the first time technology for melting ingots from spongy titanium with increased (0.08--0.45 wt.%) content of chlorine, which includes first remelting of spongy titanium in an induction furnace with a sectional mould, due to which excessive chlorine is removed. Second remelting may be performed in vacuum-arc, electron-beam or plasma-arc furnaces for reducing content of hydrogen down to the level required by GOST 19807--91.

Spongy titanium of new quality, produced in super-size apparatuses for reduction and separation, was remolten in the VD-11 vacuum-arc furnace. Ingots of 5 t mass and 780 [micro]m diameter, which meet requirements of standards for the alloy of VT1-0 grade, were manufactured.

In addition to development of commercial production of ingots from spongy titanium of new quality, experiments, connected with manufacturing of shaped titanium castings using a combined consumable electrode, consisting of two pressed and one cast billet in renovated foundry skull furnaces with non-water-cooled titanium crucible of new design, were carried out.
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Title Annotation:INFORMATION
Publication:Advances in Electrometallurgy
Date:Apr 1, 2006
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