Effect of Composition on Fracture Toughness of Ti1-xZrxN Hard Coatings
| Autor: | Chen, You-Fu, 陳宥輔 |
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| Rok vydání: | 2014 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 102 The objectives of this study were to measure the fracture toughness of Ti1-xZrxN hard coatings using the internal energy induced cracking (IEIC) method and investigate the effect of composition on the fracture toughness, from which the optimum composition for fracture toughness could be attained. Ti1-xZrxN was selected to be the model system, because Ti1-xZrxN remained single phase structure in the entire compositional range when deposited at temperatures below 500 C. Three compositions of Ti1-xZrxN, x=0.25, 0.55 and 0.85, were deposited by unbalance magnetron sputtering (UBMS). The IEIC method involved the residual stress measured by the laser curvature method, Young’s modulus obtained from nanoindentation and the film thickness from SEM cross-sectional image. The residual stress and film thickness before specimen fracture were used to determine the elastic stored energy (Gs), from which the fracture toughness could be derived. The resultant fracture toughness of Ti1-xZrxN varied with Zr fraction, ranging from 26.0 to 48.7 J/m2, and reaching a maximum for Ti0.15Zr0.85N. Adding Zr atoms into TiN could effectively increase the fracture toughness. The atomic size difference of Zr and Ti may play an important role on increase of fracture toughness. The increase of fracture toughness for Ti0.15Zr0.85N was higher than that for Ti0.75Zr0.25N. This asymmetrical behavior could be attributed to the difference in lattice constants between Ti-rich and Zr-rich compounds, in which the capability of increasing elastic stored energy may be higher for a smaller Ti atom incorporate into a larger ZrN lattice. It is also found that IEIC method can be applied as long as the cracking occurs inside the film. If the cracks penetrate into the substrate, the contribution of substrate cracking should be considered. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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