Korrelation zwischen Spannung und Haftung von Oxidschichten auf Si- und Ti-haltigen NiCrAlY-Legierungen
Korrelation zwischen Spannung und Haftung von Oxidschichten auf Si- und Ti-haltigen NiCrAlY-Legierungen
The relation between mechanical stresses and the adhesion of alumina scales on Si- and Ti-containing NiCrAlY alloys has been investigated. Therefor the Si and Ti contents in model alloys with the base compensition Ni-20Cr-10Al-Y, which were cast to achieve high purity, were varied from 0 to 2 $^{m}$...
Saved in:
Personal Name(s): | Vosberg, V. (Corresponding author) |
---|---|
Quadakkers, Willem J. / Schubert, F. / Nickel, Hubertus | |
Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich, Zentralbibliothek, Verlag
1998
|
Physical Description: |
III, 179 p. |
Document Type: |
Report Book |
Research Program: |
ohne Topic |
Series Title: |
Berichte des Forschungszentrums Jülich
3584 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
The relation between mechanical stresses and the adhesion of alumina scales on Si- and Ti-containing NiCrAlY alloys has been investigated. Therefor the Si and Ti contents in model alloys with the base compensition Ni-20Cr-10Al-Y, which were cast to achieve high purity, were varied from 0 to 2 $^{m}$/$_{0}$. These solid samples were subjected to cyclic oxidation in the temperature range from 950 to 1100°C. Growth and spallation of the oxide scale were observed by gravimetry. The stresses, present at ambient temperature, were periodically determined by X-ray stress evaluation. Using these results a reasoning of the mechanisms for stress relief and damage of the scale was carried out. The addition of Silicon as well as of Titanium has an evident influence on phase composition of Ni-20Cr-10Al-Y type alloys. Due to the variation of phase stability regions the thermal expansion is affected by these additions in the range from 950 to 1100°C. The expansion is enlarged by the addition of Si and lowered with increasing Ti content.For oxidation temperatures above 950°C a relaxation of thermally induced stresses is to be noticed, which is mainly caused by plastic deformation of the base material . The temperature above which relaxation takes effect seeins to be lowered by the addition of Si in contrast to Ti having the opposite effect. An analysis of detected defects gives indicates that shear stresses at flaws inside the oxide as well as stress concentrations at oxide intrusions contribute to oxide scales' failure. In this context there is especially the stimulation of the Formation of oxide intrusions by high Ti contents (2 $^{m}$/$_{0}$) to be noticed. A major influence on the development of defects within the oxide as well as in the interface has the variation of the Y content. Raising it from 0.1 to 0.4 $^{m}$/$_{0}$ results in an increase of precipitation of Yttrium aluminates and in an earlier failure during cyclic oxidation experiments. |