| High macroscopic residual stresses in thin coatings deposited by DC magnetron sputtering (MS) are caused by both the thermoelastic effects - thermal stress, and intrinsic stress, generated by high energetic particle bombardment during the coating deposition. In order to establish an alternative method for the study and characterization of the stress magnitude in a given coating/substrate system, this work reports an experimental technique, the electric strain extensometry (ESE), which is suggested to obtain the coating in-plane residual stresses level in a real time scale. A sensitivity analysis for in situ residual stress analysis was performed using a single active strain-gage sensor mounted in an arm of a Wheatstone bridge electric circuit. Two different coating/substrate systems - the molybdenum/glass and zirconium oxide/Ni-alloy composites were prepared by DC magnetron sputtering (MS). The residual stress values developed in both systems were used to evaluate the electrical signal magnitude that would be obtained within ESE measurements. The predicted values fit well the experimental data, moreover, being in a range of several micro-Volts, they are quite detectable by a data acquisition system. |
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