In situ hard coatings strain measurement using a commercial strain-gage device

In this work we present a novel technique which can be used to measure in s itu the induced substrate strain caused by the depositing film. The techniq ue, based on the application of a commercial strain-gage, was used during t he deposition of ultra-hard silicon carbide (SiC) films by RF magnetron spu ttering, onto thin (95 mum) martensitic stainless steel substrates. The dir ect measurement of the electrical resistance of the strain-gage provides th e strain values used to find the stress present in the film/substrate inter face. Using a value of 480 GPa for the Young modulus of the SiC film, preli minary measurements furnish a value of the residual stress sigma varying fr om 0.7 to 3 GPa, depending on the deposition conditions. These results are in good agreement with other ex situ measurements performed on the same mat erial. The strain sensibility of this technique is about 10 mum/m. (C) 2000 Elsevier Science B.V. All rights reserved.