*T. vom Braucke¹, F. Papa¹, B.D. Beake², C-H. Shin³, J-H. Yun³, N.Bierwich⁴, N. Schwarzer⁴, Ivan Fernandez Martinez⁵, J.A. Gutierrez⁵Ambiorn Wennberg^5
1GP Plasma, Medina, OH ; ²Micro Materials Ltd, Wrexham, United Kingdom; ³DONGWOO HST CO., LTD, Gyeonggi-do, Korea; ⁴Saxonian Institute of Surface Mechanics, Ummanz / Rügen, Germany; ⁵Nano4Energy SL, Madrid, Spain
Measurement of coating stress relies on a bottom up approach to model or directly measure lattice stress or stress relaxation. The methods are time consuming, costly and lack the flexibility for industrial applications and rapid development cycles. Also, several technical drawbacks limit their widespread industrial uptake. We discuss the shortcomings and the potential error and uncertainty assumptions, highlighting that we might be missing fundamental properties of interest. A solution is found overcoming these constraints to determine (relative) intrinsic stress profiles via a series of nano-indentations within a Calotte crater. This is possible by use of the fundamental equation of elasticity applied with a holistic top-down approach, including all possible uncertainties, to draw information from the indentation curve data. We demonstrate the method on relatively (~8 µm) thick HiPIMS and DLC industrial coatings on high-speed steel, comparing stress profiles to process conditions. The speed of this method to characterize stress profiles in an industrial setting allows one to understand the effects of process changes on stress as a function of depth, thus to properly design for functional use. This capability is industrially significant and future work will extend the method to absolute values and compare to other established techniques for validation.