期刊
ACTA MATERIALIA
卷 59, 期 14, 页码 5422-5433出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2011.05.015
关键词
Thin films; Raman spectroscopy; Residual stresses; Fracture; Analytical methods
资金
- University of Engineering and Technology, Lahore-Pakistan
- University of Erlangen-Nurnberg, Germany
In this study, the cracking of a brittle diamond coating on a titanium substrate under tensile straining was investigated by micro-Raman spectroscopy and analytical modelling. The in-situ micro-Raman investigations showed that the fracture strength of the coating is similar to 1.5 GPa, and it contains an initial compressive residual stress of similar to-5.4 GPa which can be reduced by the application of uniaxial tensile strain. At higher strains, the compressive stress was transformed into the tensile regime and cracks appeared in the coating, followed by a reduction in crack spacing and finally delamination. The stress measurements across different cracked coating segments, using Raman spectroscopy, indicated tensile stresses at the middle and compression near the edges of the segment under tensile load. Coating fragmentation leads to a relaxation of the stress within the cracked coating segment. Further cracking of the smaller segments requires larger strains. Here, the classical shear lag model was extended to derive the stress distribution in the coating bonded to the substrate, considering both residual stress and cracking using a fracture criterion. The effect of substrate plasticity on the evolution of residual stress and on the cracking behaviour of the coating is also introduced. A good agreement is found between the modelling approach and the measured failure behaviour as well as the stress distributions in the fractured diamond segments. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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