2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 9. Iron and Steel, Metals and Alloys
| Editors: | Kongoli F, Conejo A, Gomez-Marroquin MC |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 242 pages |
| ISBN: | 978-1-987820-77-5 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Heat-Resistant and Refractory Alloys for Special Destination
Aleksandre Kandelaki1; Omar Mikadze2; George Mikadze2; Zurab MirijanaShvili1; Vazha Garibashvili1;1FERDINAND TAVADZE INSTITUTE OF METALLURGY AND MATERIALS SCIENCE, Tbilisi, Georgia; 2GEORGIAN TECHNICAL UNIVERSITY, Tbilisi, Georgia;
Type of Paper: Regular
Id Paper: 91
Topic: 3
Abstract:
The intensive progress of the various modern technologies (aeronautics, space exploration, nuclear energy, etc.) causes the need for the new structural materials operating in extreme conditions (high temperatures, aggressive media, high mechanical loads, etc.). However, the practice shows that tailoring of materials with the combination of all required properties is a rather hard task. As a result, the technique of coating used to protect refractory matrix from corrosion- and wear-resistance, radiation, etc. acquires special relevance.
A heat-resistant high-chromium alloy (Fe-45%Cr -4% Al) doped with the rare earth metals (0.25% La or Y), was found to be a protective material to the refractory matrix [Georgian Patent, P 3273, 24.06.2002, O.Mikadze, E.Kutelia et al.].
For the reliable protection of alloys of this system from long-term oxidation, it is necessary that the formed protective layer of Al2O3 would remain entirely solid and should not exfoliate when cooled. This problem can be solved by alloying the Fe-Cr-Al matrix with highly active, primarily rare earth elements.
In the present work, for similar purposes, the authors offer an iron-chromium alloy (up to 16% Cr) doped with Zr and Ce (Fe-16%Cr-5,0%Al-0,5%Zr -0,3%Ce). Adding of Ce changes the mechanism of formation of the protective oxide (Al2O3) layer at the metal-coating interface, resulting in the improved properties (adhesion, abrasion resistance, strength characteristics, etc.).
Positive influence of Ce on the formation of a protective oxide (Al2O3) layer is enhanced by its co-doping with Zr. Here an economic aspect of the technology is an important factor - it is significantly cheaper. The reduced chromium content (to 16%) makes it possible to provide air melting under flux and fabricate the product easy to forge, roll and process by cutting.
Ingots of the produced material were prepared in magnesite crucibles by induction melting under flux. Cylindrical samples (d=10mm and h=20 mm) were cut from the ingots rolled at T≈1,000°C. The samples were tested on heat resistance (at 1,200°C and 1,300°C in the air and at 1300±50°C in the atmosphere of combustion products of gaseous fuels);
The initial stages of oxidation were studied by the method of continuous weighing on the installation 'SETARAM'; long stages - by the method of periodic weighing.
The samples of the refractory matrix were coated by using the method of electron beam evaporation followed by condensation.
Morphology of the metal-coating interface layer was studied on the SEM (DSM-960, Zeiss, Germany).
The chemical composition and the concentration distribution of the elements in the scale determined by X-ray microanalysis (COMIBAX, CAMECA).
In this way, a special alloy (Fe-16,0%Cr-5,0%Al-0,5%Zr-0,3%Се) has been developed for protective coating of heat-resistant matrix; Doping of the alloy with Zr and Ce improves some tribological properties of the coatings; The developed alloy is recommended to protect operating units of power plants from degradation of their high-temperature properties.
Keywords:
Aluminum; Iron; Technology; Temperature;References:
[1] O.I.Mikadze, E.R.Kutelia and et al. ”Special Heat Resistant and Corrosion Resistant Alloys” Georgian Patent P 3273 (2002.06.24)[2] Omar Mikadze and Aleksandre Kandelaki“ Influence of Cerium Additives on High-Temperature Corrosion of Chromium” Bull. of the Georgian National Academy of Sciences, 4, №3 (2010), 66-69
[3] Yasutoshi Saito “Effects of Rare Earth Elements of the High Temperature Oxidation of Heat Resisting Alloys”. Amsterdam-Oxford-New York-Tokyo. 1989, 227-260.
[4] O.I.Mikadze, M.N.Okrosashvili and et al. “Design of New Compositions and Technological Procedures of High-Temperature Coating on Chromium Super alloys”. Metallofiz. I NoveishieTekhnol., Kiev, 27 (2005), 1297-1305.