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Damage and adhesion of thin films

The scratch resistance of coatings is a key feature of surface durability. As a consequence, the damage of such systems has to be explored. In particular, the substrate/thin film adhesion must be well controlled and measurable. Using our experimental scratch device, allowing in-situ observation of the scratch, the fracturing of some thin coatings deposited on various substrates were investigated under different conditions of temperature and scratching speed.

A collection of fracture mechanisms were observed [1], depending on these two variables. A global energy balance model [2-3] of the stable blistering process (see video 1) which is obtained for some experimental conditions permits one to determine the adhesion of the system. The adhesion can be measured by following the delaminated area (quantified by image analysis) as a function of the scratching distance during blistering. The adhesion corresponding to different substrate/thin film systems was derived using the global energy balance model and thanks to a multi-indenter (size & roughness) approach.
This topic already leads to 3 papers and forthcoming projects with end-user companies.

Video 1

[1] V. Le Houérou, C. Robert, C. Gauthier, and R. Schirrer, Mechanisms of blistering and chipping of a scracth-resistant coating, Wear, 265 [3-4] (2008), pp. 507-515.
[2] V. Le Houérou, C. Gauthier, and R. Schirrer, Energy based model to assess interfacial adhesion using a scratch test, Journal of Materials Science, 43 (2008), pp. 5747-5754.
[3] V. Le Houérou, C. Gauthier, and R. Schirrer, Mechanical analysis of the blistering of a thin film deposited on a glassy polymer, Tribology International, 43 [1-2] (2010), pp 129-135.