<p>This Thesis presents two different deposition techniques for the synthesis of Ti<sub>2</sub>AlC coatings. First, I have fabricated Ti<sub>2</sub>AlC coatings by high velocity oxy-fuel (HVOF) spraying. Analysis with scanning electron microscopy (SEM) show dense coatings with thicknesses of ~150 µm when spraying with a MAXTHAL 211<sup>TM </sup>Ti<sub>2</sub>AlC powder of size ~38 µm in an H<sub>2</sub>/O<sub>2</sub> gas flow. The films showed good adhesion to stainless steel substrates as determined by bending tests and the hardness was 3-5 GPa. X-ray diffraction (XRD) detected minority phases of Ti<sub>3</sub>AlC<sub>2</sub>, TiC, and Al<sub>x</sub>Ti<sub>y</sub> alloys. The use of a larger powder size of 56 µm resulted in an increased amount of cracks and delaminations in the coatings. This was explained by less melted material, which is needed as a binding material. Second, magnetron sputtering of thin films was performed with a MAXTHAL 211<sup>TM</sup> Ti<sub>2</sub>AlC compound target. Depositions were made at substrate temperatures between ambient and 1000 °C. Elastic recoil detection analysis (ERDA) shows that the films exhibit a C composition between 42 and 52 at% which differs from the nominal composition of 25 at% for the Ti<sub>2</sub>AlC-target. The Al content, in turn, depends on the substrate temperature as Al is likely to start to evaporate around 700 °C. Co-sputtering with Ti target at a temperature of 700 °C, however, yielded Ti<sub>2</sub>AlC films with only minority contents of TiC. Thus, the addition of Ti is suggested to have two beneficial roles of balancing out excess of C and to retain Al by providing for more stoichiometric Ti<sub>2</sub>AlC synthesis conditions. Transmission electron microscopy and X-ray pole figures show that the Ti<sub>2</sub>AlC grains grow in two preferred orientations; epitaxial Ti2AlC (0001) // Al2O3 (0001) and with 37° tilted basal planes of Ti<sub>2</sub>AlC (101̅7) // Al<sub>2</sub>O<sub>3</sub> (0001).</p> / Report code: LIU-TEK-LIC-2008:15.
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:liu-11422 |
| Date | January 2008 |
| Creators | Frodelius, Jenny |
| Publisher | Linköping University, Linköping University, Thin Film Physics, Institutionen för fysik, kemi och biologi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, text |
| Relation | Linköping Studies in Science and Technology. Thesis, 0280-7971 ; 1357 |
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