A methodology for obtaining plasticity characteristics of metallic coatings via instrumented indentation

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• 作者：J.L. Reed^a ; J. Dean^a ; ^b ; G. Aldrich-Smith^c ; T.W. Clyne^a ; ^{twc10@cam.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Indentation ; Finite element analysis ; Coatings ; Plasticity
• 刊名：International Journal of Solids and Structures
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：80
• 期：Complete
• 页码：128-136
• 全文大小：3615 K

文摘

A methodology is presented for inferring the yield stress and work-hardening characteristics of metallic coatings from indentation data. It involves iterative use of FEM modelling, with predicted outcomes (load–displacement relationships and residual indent shapes) being systematically compared with experimental data. The cases being considered are ones in which the indenter penetration depth is a significant fraction of the coating thickness, so that the properties of the substrate, and possibly of the interface, are of significance. The methodology is thus suitable for the testing of thin coatings. In the present work, the coatings were in fact relatively thick (hundreds of microns) and the (spherical) indenter penetration was a substantial fraction of this. In this way, the basic validity of the methodology could be investigated with minimal complications from effects related to microstructure, oxide films, surface roughness etc. Furthermore, the properties of both coating and substrate (in the through-thickness direction) were established separately via conventional compression testing. The systems studied were copper (yield stress ∼15 MPa) on stainless steel (yield stress ∼350 MPa) and vice versa. Both exhibited significant work hardening. It is concluded that the methodology is basically reliable, with relatively good sensitivity and resolution, although this does depend on several factors, which are highlighted in the paper. It is unlikely to be suitable for very thin (sub-micron) films, but should be reasonably accurate for coatings of thickness down to a few microns.