Optimized Design of Surface Mechanical Testing Procedures

Marco Di Donato, Anton Paar, Switzerland

Since the early 1990s, coatings have been routinely characterized using nanoindentation, scratch testing and tribology testing in order to optimize them for their applications.

Most of the current international standards were written during the same period and unfortunately most users of mechanical testers only compare values between hardness, elastic modulus, critical loads, friction and wear but these may be insufficient for a good understanding of a coating design.

Optimization of a coating remains a challenge due to the many influencing variables such as coating adhesion, yield and wear mechanism, thermal and mechanical stresses, etc.

By the use of measured data from a Nanoindentation test, a physical calculation of spatial stress profiles is simulated considering realistic material properties.

This analysis allows the user to perform real dimensioning of sophisticated scratch and tribology tests so that they are focused at specific regions in the coating design architecture.

This procedure allows more specific investigations of critical interfaces, transition layers and substrate regions with adjusted depth resolution.

Due to roughness and surface structure such optimized scratch, groove or tribology tests sometimes even need to take into account the true topography of the sample surface before and after the test. Such 3D scratch or tribology tests can provide much more information about the material stability and reliability than do classical approaches.

Using this valuable approach to quantify the interfaces between layer and substrate in a coating design allows a faster optimization of the coating design thus providing significant cost reduction.

To illustrate the features of this optimization method, various examples of characterization on coated samples will be presented, showing the flexibility of the technique for different situations.

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