| 1. |
- Frodelius, Jenny, et al.
(författare)
-
Ti2AlC coatings deposited by High Velocity Oxy-Fuel spraying
- 2008
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 202:24, s. 5976-5981
-
Tidskriftsartikel (refereegranskat)abstract
- High Velocity Oxy-Fuel has been utilized to spray coatings from Ti2AlC (MAXTHAL 211®) powders. X-ray diffraction showed that the coatings consist predominantly of Ti2AlC with inclusions of the phases Ti3AlC2, TiC, and Al–Ti alloys. The fraction of Ti2AlC in coatings sprayed with a powder size of 38 μm was found to increase with decreasing power of the spraying flame as controlled by the total gas flow of H2 and O2. A more coarse powder (56 μm) is less sensitive to the total gas flow and retains higher volume fraction of MAX-phase in the coatings, however, at the expense of increasing porosity. X-ray pole figure measurements showed a preferred crystal orientation in the coatings with the Ti2AlC (000l) planes aligned to the substrate surface. Bending tests show a good adhesion to stainless steel substrates and indentation yields a hardness of 3–5 GPa for the coatings sprayed with a powder size of 38 μm.
|
|
| 2. |
- Sonestedt, Marie, 1981
(författare)
-
Microstructure and oxidation behavior of High Velocity Oxy-Fuel spray deposited Ti2AlC coatings
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ti2AlC is one of the ternary carbides in the MAX phase group of materials. This group of materials have a unique combination of ceramic and metallic properties, such as machinability, high thermal conductivity, low density and oxidation resistance. The aim of this work is to produce thick coatings with good mechanical and thermal properties that can be used for example to operate as protection of structural materials against high temperature oxi- dation. Previously, Ti2AlC has only been fabricated as bulk and thin film. In this work it is shown that high velocity oxy-fuel spraying with Ti2AlC powder can be used to deposit relatively dense, 200 µm thick coatings. This study demonstrates that the Ti2AlC powder decompose during the spraying process. The resulting microstructure consists mainly of large Ti2AlC grains and regions of small TiC grains embedded in TixAly. These grains and regions are surrounded by oxidized zones. The study of the effect of process parameters reveal that it is possible to increase the amount of MAX phase present in the coatings using powder with a larger grain size. However, this can also have an adverse effect on porosity and thickness of the coatings. The reputation of good oxidation resistance for bulk Ti2AlC is reinforced in this work. The oxidation study shows that bulk Ti2AlC forms protective α-Al2O3 already at 700◦C. For the coatings the oxidation behavior is much more complex as they consist of different phases. The occurrence of Al2O3 in the coatings is observed in the investigated temperature range (700-1200◦C).However it does not form a continuous layer essential for good protection of the substrate. Further work is necessary to bring the good oxidation resistance into a coating.
|
|
| 3. |
|
|
| 4. |
- Sonestedt, Marie, 1981, et al.
(författare)
-
Microstructure of high velocity oxy-fuel sprayed Ti2AlC coatings
- 2010
-
Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 45:10, s. 2760-2769
-
Tidskriftsartikel (refereegranskat)abstract
- The microstructure formation and phase transformations in Ti2AlC-rich coatings deposited by High Velocity Oxy-fuel spraying of Maxthal 211(A (R)) powders is presented. High resolution electron microscopy analysis, using both scanning and transmission electron microscopy with energy dispersive spectrometry and energy filtering, combined with X-ray diffraction reveals that the coatings consist of Ti2AlC grains surrounded by regions of very small TiC grains embedded in Ti (x) Al (y) . The composition of the Ti (x) Al (y) depends on its surrounding and varies with size and distribution of the adjacent TiC grains. Impact of spray parameters on coating microstructure is also discussed. Two spray parameters were varied; powder size distribution and flame power. They were found to greatly affect the coating microstructure. Increasing powder size and decreasing flame power increase the amount of Ti2AlC, but produces thinner coatings with lower cohesion. Larger powder size will also decrease oxygen incorporation.
|
|
| 5. |
- Sonestedt, Marie, 1981, et al.
(författare)
-
Oxidation of Ti2AlC bulk and spray deposited coatings
- 2010
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 52:12, s. 3955-3961
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation behaviour of Ti2AlC bulk and high velocity oxy-fuel spray deposited coatings has been investigated for temperatures up to 1200 degrees C. X-ray diffraction and electron microscopy show that bulk Ti2AlC forms a continuous layer of alpha-Al2O3 below a layer of TiO2 at temperatures as low as 700 degrees C. Oxidation of the Ti2AlC coatings is more complex, and also involves the phases Ti3AlC2, TiC, and TixAly, formed during the spraying process. alpha-Al2O3 is observed, however, it is unevenly distributed deep into the material, and does not form a continuous layer essential for good oxidation resistance.
|
|
| 6. |
- Sonestedt, Marie, 1981, et al.
(författare)
-
Using atom probe tomography to analyse MAX-phase materials
- 2011
-
Ingår i: Ultramicroscopy. - : Elsevier BV. - 1879-2723 .- 0304-3991. ; 111:6, s. 642-647
-
Tidskriftsartikel (refereegranskat)abstract
- Ti2AlC belongs to an interesting group of materials with both metallic and ceramic properties. This material is highly attractive as a candidate for corrosion resistant coatings. The process of fabrication of such coatings is in the investigation stage only and the detailed knowledge of the structure and chemistry of the produced coatings is important for optimisation of their properties. In this work the applicability of atom probe tomography for investigation of both Ti2AlC bulk materials and coatings was tested. We show that for the first time, Ti2AlC has successfully been analysed using laser pulsing mode in a local electrode atom probe and the results from analysis of both bulk Ti2AlC and Ti2AlC based spray deposited coatings are presented. It appears that, in this particular material system, it is difficult to obtain the accurate stoichiometry. This is due to the loss of detection because of unavoidable multiple events and due to the peak overlaps present. Methods of how to approach these problems are discussed.
|
|
| 7. |
- Thuvander, Mattias, 1968, et al.
(författare)
-
Quantitative atom probe analysis of carbides
- 2011
-
Ingår i: Ultramicroscopy. - : Elsevier BV. - 1879-2723 .- 0304-3991. ; 111:6, s. 604-608
-
Tidskriftsartikel (refereegranskat)abstract
- Compared to atom probe analysis of metallic materials, the analysis of carbide phases results in an enhanced formation of molecular ions and multiple events. In addition, many multiple events appear to consist of two or more ions originating from adjacent sites in the material. Due to limitations of the ion detectors measurements generally underestimate the carbon concentration. Analyses using laser-pulsed atom probe tomography have been performed on SiC, WC, Ti(C,N) and Ti 2 AlC grains in different materials as well as on large M 2 3C 6 precipitates in steel. Using standard evaluation methods, the obtained carbon concentration was 6-24% lower than expected from the known stoichiometry. The results improved remarkably by using only the 13 C isotope, and calculating the concentration of 12 C from the natural isotope abundance. This confirms that the main reason for obtaining a too low carbon concentration is the dead time of the detector, mainly affecting carbon since it is more frequently evaporated as multiple ions. In the case of Ti(C,N) andTi 2 AlC an additional difficulty arises from the overlap between C 2 + ,C 2+ 4 and Ti 2+ at the mass-to-charge 24 Da. © 2010 Elsevier B.V.
|
|
