Oxidation Protection of Titanium Aluminides and Ni-Base Superalloys at High Temperatures by the Halogen Effect – Principles and Applications

2011 ◽  
Vol 696 ◽  
pp. 366-371 ◽  
Author(s):  
Hans Eberhard Zschau ◽  
Michael Schütze
Keyword(s):  
Metal Oxide ◽  
Titanium Aluminides ◽  
Slow Growth ◽  
Alumina Scale ◽  
Oxide Interface ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
Oxidation Protection ◽  
The Stability ◽  
Distinct Maximum

The oxidation protection of TiAl-alloys at temperatures above 750°C can be improved by the fluorine effect. The results of thermodynamical calculations predict a corridor for a positive fluorine effect. Ion implantation of F was performed because of giving the best results. After a high F-loss during heating a thin protective alumina scale acts as a diffusion barrier. The F-depth profiles show a distinct maximum at the metal/oxide interface. The diffusion coefficient of F in TiAl for 900°C was determined. The stability of the F-effect after long oxidation time at 900°C and 1000°C can be explained by the existence of a constant F-amount at the metal/oxide interface ensuring a slow growth of the alumina scale. The fluorine effect was also applied to Ni-base superalloys to improve their high temperature oxidation resistance by forming a dense continuous protective alumina scale.

Effect of Silicon on High Temperature Oxidation Of Stainless Steels★

CORROSION ◽  
1959 ◽  
Vol 15 (11) ◽  
pp. 73-77 ◽  
Author(s):  
JOHN F. RADAVICH
Keyword(s):  
Metal Oxide ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Stainless Steels ◽  
Oxide Films ◽  
Fluorescence Analysis ◽  
X Ray Diffraction ◽  
Oxide Interface ◽  
Temperature Oxidation ◽  
X Ray

Abstract Growth of oxide films at 600 and 800 C on a series of 16 Cr-10 Ni-bal Fe stainless steels with silicon contents ranging from 0.17 to 3.55 percent was studied by electron microscopy, electron diffraction, X-ray diffraction and X-ray fluorescence analysis techniques. Oxide scales and sub-scales formed during oxidation at 1000 C were studied optically in cross section as well as by X-ray diffraction and fluorescence analysis. Results show that as silicon content increases oxidation resistance increases rapidly until at the high silicon level, 3.55 percent, a very thin oxide film is formed at 60u and 800 G and very little oxide scale forms at 1000 C. Mechanism of oxidation resistance imparted by silicon appears to be that it decreases the number of defects in the initial oxide films formed at the metal-oxide interface. With a lesser number of defects in the thin film, an enrichment of Cr at the metal-oxide interface and in the oxide films occurs and the rate of diffusion of iron outward to form the oxide scale is greatly retarded. 2.3.7

Comparison of Fluorination Treatments to Improve the High Temperature Oxidation Resistance of TiAl Alloys in SO2 Containing Environments

2010 ◽  
Vol 638-642 ◽  
pp. 1374-1378 ◽  
Author(s):  
Patrick J. Masset ◽  
Rossen Yankov ◽  
Andreas Kolitsch ◽  
Michael Schütze
Keyword(s):  
High Temperature ◽  
Sulfur Dioxide ◽  
Ion Implantation ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Titanium Aluminides ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
Plasma Immersion Ion Implantation

Surfaces of titanium aluminides were treated by fluorine either physically using Plasma Immersion Ion Implantation (PI³) or chemically with a F-based polymer. By controlling the fluorination parameters, both treatments improve the oxidation resistance even in the presence of sulfur dioxide (0.1 vol%). No sulfur was detected in the oxide scale although thermodynamic calculations predict the formation of sulfides. The inward diffusion of oxygen and nitrogen in the alloy was found to be reduced in the presence of SO2.

Comparison of Different Fluorine Treatments for the Protection of TiAl-Alloys Against High Temperature Oxidation

2010 ◽  
Vol 638-642 ◽  
pp. 1294-1299 ◽  
Author(s):  
Alexander Donchev ◽  
Michael Schütze
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Oxidation Mechanism ◽  
Surface Region ◽  
Alumina Scale ◽  
Jet Engines ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
Long Term Stability ◽  
One Year

The oxidation resistance of TiAl-alloys can be improved by several orders of magnitude by treating the surface of the materials with small amounts of halogens especially Cl and F. The oxidation mechanism changes due to the so called halogen effect. The formation of a fast growing mixed oxide scale on untreated alloys is suppressed, instead a thin protective alumina scale is formed on samples after optimum treatment. The different methods only influence the surface region of the components so that the bulk properties are not affected. Recent results achieved with complex TiAl-samples showed the potential that the fluorine effect could be used for TiAl-components in several high temperature applications e.g. jet engines. TiAl-specimens were treated with fluorine and chlorine in several ways and their performance during high temperature oxidation tests in air was investigated. Results of isothermal and thermocyclic oxidation tests are presented. The long term stability of the fluorine effect lasted for at least one year under thermocyclic exposure at 900°C in laboratory air. The results are discussed in terms of later use of the fluorine effect for technical applications.

Void Formation and Filling under Alumina Scales Formed on Fe-20Cr-5Al Alloy Thin Foils

2008 ◽  
Vol 595-598 ◽  
pp. 1093-1101 ◽  
Author(s):  
D.J. Potter ◽  
G.J. Tatlock
Keyword(s):  
Metal Oxide ◽  
Void Formation ◽  
Thin Foil ◽  
Alumina Scale ◽  
Oxidation Behaviour ◽  
Sustainable Growth ◽  
Aluminium Content ◽  
Oxide Interface ◽  
Thin Foils ◽  
Electron Microscopes

The oxidation behaviour and the subsequent chemical failure of a Fe-20Cr-5Al based alloy were studied at 1200°C in laboratory air, at times of up to 700 hours. Tests on 70 micron thick foils, showed void formation at the metal/oxide interface soon after the aluminium content in the alloy dropped below a critical level (≤0.5 wt%). At this stage, the alloy could no longer sustain alumina scale formation and resulted in the initiation and development of a Cr-rich sub-layer. This chromia layer was found to be continuous and of a uniform thickness. As the sub-layer formed, voids were also observed at the metal/oxide interface. The voids were found to fill with chromia after further exposure. It is thought that the change in oxide growth mechanism from alumina to chromia growth is responsible for the void formation. This also explains the lack of void formation during the sustainable growth of the alumina scale. The introduction of silicon to the Fe-20Cr-5Al based alloy via a diffusion couple was found to significantly influence the oxidation behaviour of the thin foils. Void formation was observed directly beneath the alumina scale and filled voids were now found to contain silicon oxide rather than chromia. The void filling mechanism also appeared to be different. With chromia filled voids, the filling commenced from the underside of the oxide, with the oxide growing inwards, while silica containing voids were filled by silica growing outwards into the void from the substrate. Throughout the study, optical and scanning electron microscopes were used to analyse all stages of oxidation and the subsequent failure of the thin foil samples. EBSD was also used to generate a more comprehensive analysis of selected locations.

High Temperature Oxidation Protection of Multi-Phase Mo-Containing TiAl-Alloys by the Fluorine Effect

2012 ◽  
Vol 1516 ◽  
pp. 95-100 ◽  
Author(s):  
Alexander Donchev ◽  
Raluca Pflumm ◽  
Svea Mayer ◽  
Helmut Clemens ◽  
Michael Schütze
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Titanium Aluminides ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
Β Phase ◽  
Multi Phase ◽  
The Impact

ABSTRACTIntermetallic titanium aluminides are potential materials for application in high temperature components. In particular, alloys solidifying via the β-phase are of great interest because they possess a significant volume fraction of the disordered body-centered cubic β-phase at elevated temperatures ensuring good processing characteristics during hot-working. Nevertheless, their practical use at temperatures as high as 800°C requires improvements of the oxidation resistance. This paper reports on the fluorine effect on a multi-phase TiAl-alloy in the cast and hot-isostatically pressed condition at 800°C in air. The behavior of the so-called TNM material (Ti-43.5Al-4Nb-1Mo-0.1B, in at %) was compared with that of two other TiAl-alloys which are Nb-free and contain different amounts of Mo (3 and 7 at%, respectively). The oxidation resistance of the fluorine treated samples was significantly improved compared to the untreated samples. After fluorine treatment all alloys exhibit slow alumina kinetics indicating a positive fluorine effect. Results of isothermal and thermocyclic oxidation tests at 800°C in air are presented and discussed in the view of composition and microstructure of the TiAl-alloys investigated, along with the impact of the fluorine effect on the oxidation resistance of these materials.

Influence of Pt on the metal–oxide interface during high temperature oxidation of NiAl bulk materials

2009 ◽  
Vol 51 (3) ◽  
pp. 539-546 ◽  
Author(s):  
H. Svensson ◽  
M. Christensen ◽  
P. Knutsson ◽  
G. Wahnström ◽  
K. Stiller
Keyword(s):  
High Temperature ◽  
Metal Oxide ◽  
High Temperature Oxidation ◽  
Oxide Interface ◽  
Bulk Materials ◽  
Temperature Oxidation

Optimization of the Fluorine Effect for Improving the Oxidation Resistance of Tial-Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 1061-1065 ◽  
Author(s):  
Alexander Donchev ◽  
Michael Schütze ◽  
Andreas Kolitsch ◽  
Rossen Yankov
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Inorganic Compounds ◽  
Oxidation Mechanism ◽  
Surface Region ◽  
Alumina Scale ◽  
Temperature Oxidation ◽  
Bulk Properties ◽  
Tial Alloys

The oxidation resistance of TiAl-alloys can be improved drastically by treating the surface of the components with small amounts of fluorine. The oxidation mechanism is changed. Hence, the formation of a fast growing mixed oxide scale on untreated alloys is suppressed. Instead a thin protective alumina scale is formed on samples after fluorine treatment. The different methods only influence the surface region of the components so that the bulk properties are not affected. Recent results achieved with F-containing inorganic compounds showed that the fluorine effect can be improved even further. TiAl-specimens were treated only with fluorine and with F-containing compounds in several ways and their performance during high temperature oxidation tests in air was investigated. Results of isothermal and thermocyclic oxidation tests are presented. The results are discussed in terms of a later use of the fluorine effect for technical applications.

Effective Fluorine Treatment for Improved High Temperature Oxidation Behavior of Novel Cu, Mo and Si Containing TiAl-Alloys

2014 ◽  
Vol 783-786 ◽  
pp. 1117-1122
Author(s):  
Alexander Donchev ◽  
M. Galetz ◽  
M. Schütze
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Titanium Aluminides ◽  
Turbine Blades ◽  
Surface Region ◽  
Alumina Layer ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
High Temperature Oxidation Behavior

Intermetallic light weight TiAl-alloys are expected to replace the heavy Ni-based super alloys in several high temperature applications. However until now they cannot be used at temperatures above 700°C for longer times due to their insufficient oxidation resistance. The high temperature oxidation behavior can be improved drastically for the use at temperatures up to at least 1050°C by small amounts of fluorine in the surface region of TiAl-components. A thin protective alumina layer is formed after an optimized fluorine treatment during exposure in oxidizing high temperature environments. Results of isothermal and thermocyclic high temperature oxidation tests of untreated and halogen treated TiAl-samples of new types of TiAl-alloys containing Mo, Cu and Si will be presented in this paper. These results will be compared and discussed considering the beneficial effect of fluorine for a later use as e.g. turbine blades in jet engines. Key words: Titanium aluminides, high temperature oxidation, halogen effect,

Evolution of the metal–oxide interface during the initial stage of the high temperature oxidation of ferritic stainless steels

2011 ◽  
Vol 28 (4) ◽  
pp. 274-278 ◽  
Author(s):  
Jérôme Issartel ◽  
Sébastien Martoia ◽  
Frédéric Charlot ◽  
Valérie Parry ◽  
Yves Wouters ◽  
...  
Keyword(s):  
High Temperature ◽  
Metal Oxide ◽  
Stainless Steels ◽  
High Temperature Oxidation ◽  
Oxide Interface ◽  
Temperature Oxidation ◽  
Ferritic Stainless Steels ◽  
Initial Stage
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