Application Note | Nano Scratch
Microstructure Scratch Resistance With Nano Scratch Testing
Finding Where a Coated Microstructure Starts to Crack at Millinewton Loads
Research & Experimental Testing
Jorge Ramirez
Visual Design & Editorial
Andrew Shore
Introduction
A microstructure can be made up of a prepared surface or a thin layer of material, whether metallic, polymeric, ceramic or composite. These surfaces are often confined to limited, extremely sensitive areas, and the analysis of their resistance is often a crucial factor. The quality control of these surfaces is of great interest in optics, electronics and other micro-manufactured parts in which surface properties are essential.
Importance of Nano Scratch Testing for Quality Control
The physical properties of materials are often affected by changes related to micro-scale applications. For example, changes in stresses in the materials can affect their final resistance to scratches or dents. This is why the study of scratch resistance on microstructures is critical to many applications. Nano scratch testing is an ideal tool to measure the scratch resistance of microstructures, and it is often important for the manufacturer to understand and monitor at what level marring can occur.
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Measurement Objective
We simulate the process of scratching in a controlled and monitored manner to observe the sample’s behavior. In this application, the NANOVEA Mechanical Tester in its nano scratch mode is used to measure the load required to cause failure of a microstructure, using a diamond-tipped stylus at a progressive load from 10 mN to 20 mN. The point where the coating fails by cracking is taken as the point of failure.
NANOVEA PB1000 Large Platform
Mechanical Tester
Test Parameters
| Parameter | Value |
|---|---|
| Load type | Progressive |
| Initial load | 10 mN |
| Final load | 20.00 mN |
| Loading rate | 20.00 mN/min |
| Scratch length | 100 µm |
| Indenter geometry | 90° conical |
| Indenter tip radius | 2 µm |
| Indenter material (tip) | Diamond |
Table 1: Test parameters.
Results
The normal force, frictional force and penetration were recorded along the scratch (Fig. 2), and the scratch was examined under the microscope from its start to the point of failure (Fig. 3).
Conclusion
As seen in our analysis, the scratch resistance level of the microstructure has been identified. The coating is prone to cracking and should be further investigated as to how this relates to its intended resistance level and performance. If the adhesion were not strong enough, full or partial delamination would occur at the coating-substrate interface. The value of nano scratch testing for this application is the ability to quantify the scratch resistance of the microstructure with superior repeatability. This test either simulates handling of the microstructure or quantifies its fracture toughness.
The NANOVEA Mechanical Tester in nano scratch mode is an excellent tool for the quality control of nano coatings on a wide range of substrates. The failure points obtained can be quantitatively identified to ensure quality control and performance. The same instrument can be used in the indentation and wear modes to study other properties in very limited areas of a few microns.
Frequently Asked Questions About Nano Scratch Testing of Microstructures
What is a microstructure in this context?
A prepared surface or thin layer of metallic, polymeric, ceramic or composite material confined to small, sensitive areas, as in optics, electronics and other micro-manufactured parts.
Why test microstructures by nano scratch?
Micro-scale changes such as internal stresses affect resistance to scratches and dents, and manufacturers need to know at what level marring occurs.
How was the test run?
A progressive load from 10 mN to 20 mN at 20 mN/min over a 100 µm scratch, with a 90° conical diamond tip of 2 µm radius.
What failure was seen?
The coating cracked from a point partway along the scratch; no full or partial delamination occurred at the coating-substrate interface, so adhesion held.
What does the test simulate?
Either handling of the microstructure, or a measure of its fracture toughness.
What else can be measured in such small areas?
Indentation and wear modes of the same instrument study other properties in areas of a few microns.
