| 1. |
- Curry, Nicholas, 1984-, et al.
(author)
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Impact of impurity content on the sintering resistance of dysprosia and yttria stabilised zirconia thermal barrier coatings
- 2013
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In: Proceedings of the International Thermal Spray Conference. - : ASM International. - 9781632666819 ; , s. 557-563
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Conference paper (peer-reviewed)abstract
- Dysprosia stabilised zirconia (DySZ) is a promising candidate to replace yttria stabilised zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high temperature sintering behaviour. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and yttria stabilised zirconia coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 hours at a temperature of 1150°C. Samples were subsequently measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes due to sintering.
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| 3. |
- List, A, et al.
(author)
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Mechanical properties of cold-sprayed Ti-6Al-4V coatings
- 2013
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In: Proceedings of the International Thermal Spray Conference. - : ASM International. - 9781632666819 ; , s. 155-160
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Conference paper (peer-reviewed)abstract
- Titanium and titanium alloys are of great interest in aerospace and medical industries. Especially, Ti-6Al-4V alloys show a unique combination of high mechanical strength, low density and an outstanding corrosion resistance. However, particularly the high strength restricts industrial processing procedures. Thus, there are increasing demands for powder metallurgical process routes. For pure titanium, cold spraying already proved to be a promising alternative for manufacturing semi-finished products, mainly due to the use of high process gas temperatures and pressures. Nevertheless, due to the higher material strength, the production of Ti-6Al-4V coatings by cold spraying is still challenging, even under higher process parameters. The present study deals with the production and characterization of Ti-6Al-4V coatings produced by cold spraying. All experiments were performed using nitrogen as process gas. By a systematic variation of the spray parameters up to a process gas temperature of 1000°C and a process gas pressure of 5 MPa, the coatings could be tuned for optimum mechanical properties. In addition, attainable coating properties are described in terms of a newly introduced coating quality parameter η, namely the ratio of the particle velocity to the critical velocity, to reveal the most significant influences on coating performance and to give hints for further optimization.
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