||A Polarization Study of nc-TiC/a-SiC
||Hansen, Eigil Ottesen (Materialeteknologi og -udvikling, Institut for Produktion og Ledelse, Danmarks Tekniske Universitet, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Møller, Per (Materials Science and Engineering, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Ambat, Rajan (Materials Science and Engineering, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Leisner, Peter (Acreo AB)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||Ceramics are interesting for contact applications because they have a low wear rate and are arc resistant. MAX phases are a group of ceramics that combine electrical conductivity with a low wear rate. MAX phases are also ductile and show resistance towards arcing. Thin film application of MAX phases has shown promising results as they are also electrical conducting and ductile. They are however not stoichiometric MAX phases. It is therefore a goal to investigate these new thin films, which in this thesis have a composition of nanocrystalline titanium carbide embedded in an amorphous silicon carbide (nc-TiC/a-SiC).
This thesis has investigated coatings nc-TiC/a-SiC and alloys of this on a titanium substrate. Polarization experiments have determined that nc-TiC/a-SiC oxidize when in contact with atmospheric air, and while being polarized (electrochemically) further oxidation takes place. This oxidation affects titanium, silver, and palladium. The oxides expand and put strain on the coating, which eventually will break and result in delamination.
Pourbaix diagrams show areas of corrosion for all coatings from low to high pH values.
Current densities for all coatings are high and will therefore corrode fast after a corrosion cell has formed. This will either result in either delamination or a heavy oxide layer. Both will result in contact failure.
Creation date: 2007-07-25
Update date: 2011-09-22