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Creating a TiAlN/ZrN Superlattice Nnanostructured Coating using Physical Vapour Deposition and Evaluating Coating Hardness

Monfared, Ali Akbar | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57137 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Dolati, Abolqasem
  7. Abstract:
  8. Despite the wide application of physical vapor deposition coating in various industries, one of the most important challenges is to achieve super hard coating with the help of this method. Super-hard coatings are coatings whose hardness is greater than 40 GPa. So far, various researches have been done to achieve this goal. One of the most important methods that has made it possible to achieve this goal is the creation of nanostructured coatings. Nanostructured coatings that cause a significant increase in hardness include superlattices and nanocomposites. In superlattice coatings, two layers with different shear modulus and lattice constant are deposited to each other with a very low thickness (below 10 nm) alternately until the thickness of the entire coating reaches the range of 2 to 4 microns. The repetition period of the layers is called the modulation period Λ, which is the most important parameter affecting the hardness of these coatings. In this research, each of ZrN and TiAlN single-layer coatings with a thickness of 4 microns were formed and their hardness was obtained as 23 and 27 GPa respectively. Then, ZrN/TiAlN superlattice coating with different modulation period in the range of 7.2 nm to 3.6 nm was created by physical vapor deposition method and their hardness was measured by nanoindentation method. First, the superlattice coating with the longest modulation period (7.2 nm) was formed and its hardness was 24.6 GPa. In the next step, the hardness of the coating with the modulation period of 6.8 nm was 25.51 GPa, which shows the increasing trend of hardness with decreasing modulation period. By further reducing the modulation period, the hardness of the coating increases and reaches a maximum value of 41.46 GPa in the modulation period of 4.4 nm, and then with the further reduction of the modulation period, the hardness becomes a downward trend and reaches a value of 27.25 GPa in the modulation period of 3.6 nm. The result is that the thickness of the layers is the most important parameter in the hardness of the ZrN/TiAlN superlattice coating. So that in only one optimal thickness, it is possible to reach a hardness above 40 GPa, and in more or less thicknesses, the hardness does not differ much from the hardness of each of the ZrN and TiAlN layers
  9. Keywords:
  10. Physical Vapor Deposition ; Nanostructured Coating ; Superlattice Coating ; ZrN/TiAlN Superlattice ; Superhard Coating

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