2014-Sustainable Industrial Processing Summit
SIPS 2014 Volume 5: Composite, Ceramic, Quasi-crystals, Nanomaterials & Coatings
| Editors: | Kongoli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2014 |
| Pages: | 578 pages |
| ISBN: | 978-1-987820-07-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
CD shopping page
Recent developments in surface protection of titanium and titanium-aluminum alloys against environmental degradation at elevated temperatures
Rossen Yankov1; Johannes von Borany1; Patrick Masset2; Alexander Donchev3; Michael Schuetze3;1INSTITUTE OF ION BEAM PHYSICS AND MATERIALS RESEARCH, HELMHOLTZ-ZENTRUM DRESDEN-ROSSENDORF (HZDR), Dresden, Germany (Deutschland); 2FRAUNHOFER UMSICHT, Sulzbach-Rosenberg, Germany (Deutschland); 3DECHEMA FORSCHUNGSINSTITUT, Frankfurt am Main, Germany (Deutschland);
Type of Paper: Plenary
Id Paper: 390
Topic: 17
Abstract:
Titanium and its alloys with aluminum are lightweight structural materials, which find ever-increasing use in a number of advanced aerospace, automotive and power generation applications. These materials, however, are limited in applicability by their inadequate oxidation resistance at elevated temperatures (> 500AoC for Ti, and > 750AoC for TiAl).
This talk reviews recent advances in using state-of-the-art techniques for surface engineering of Ti, Ti-base alloys and I3-TiAl intermetallics, with a view to rendering them resistant to high-temperature environmental oxidation and oxygen embrittlement.
The first part of the talk covers the surface modification of Ti and low-Al-content Ti-base alloys by using combined techniques involving either aluminization followed by plasma immersion ion implantation (PIII) of fluorine or formation of a surface barrier coating by magnetron sputter co-deposition of Ti and Al followed by vacuum annealing and PIII of F.
The second part focuses on the direct surface treatment of I3-TiAl by PIII of F. Such type of fluorination enables the F-implanted alloy surface to develop a stable, adherent and highly protective alumina scale upon subsequent oxidation in air at temperatures in excess of 1000AoC for extended exposure times.
The last part deals with the fabrication of protective TiAl coatings using a two-step coating scheme. First, an Al-rich TiAl layer is formed on the I3-TiAl alloy by either MO-CVD, PVD or thermal spraying. Then the TiAl layer is treated by PIII of F. The resulting coatings are tested for oxidation resistance, oxygen embrittlement, and retention of mechanical properties. A combination of an Al-rich CVD coating and treatment by PIII of F gives the best results. An example is also given of a thermal barrier coating whose structure comprises, instead of a bond coat, a thin alumina layer formed by PIII of F and subsequent high-T oxidation. The results of these studies have been helpful in understanding the oxidation behavior of the surface-engineered alloys from both a scientific and a technological standpoint.