Micro-Scratch Testing

Frictional load s - Normal load Sliding distance 

By replacing the diamond tip indentor with a small steel ball, the characteristic wear and failure events are very similar, although they do not appear so clearly.  

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FIG. 4—Micro-scratch test data for thin hard coatings. 

Gitis, N. and Vinogradov, M., patent of Micro-scratch Test Indentation and Method of Micro-scratch Testing, 1999. 

Micro-Scratch Testing and Finite Element Simulation of Wear Mechanisms of Polymer Composites... 

Chapter 7 Micro-Scratch Testing and FE Simulation of Wear... 

Recently, Sarin (1995) developed a new version of the scratch test, who turned the experiment on its side and performed a micro-scratch test on the cross section of the sample, as shown in Fig. 22.11. After the edge of the cross section is precisely polished, the scratch test is carried out on a microscopic scale. As a result, the failure mode can be isolated and... 

Sarin VK (1995) Micro-scratch test for adhesion evaluation of thin films. In Mittal KL (ed) Adhesion measurement of films and coatings. VSP, Utrecht, p 175... 

V.K. Sarin, Micro-Scratch test for adhesion evaluation of thin films, in K.L. Mittal (Ed.), Adhesion Measurement of Films and Coatings, VSP BV Publishing, 1995, p. 175. 

Dynamic nanohardness, elastic modulus, friction coefficient and dynamic scratch-depth were measured by a NanoTest 600 nano-mechanical tester (Micro Materials Ltd., UK) [17], A Berkovich type indenter-head was applied for hardness measurements in depth control mode with 50 nm maximum penetration, while a Sharp Rockwell head was used for scratch-tests with 1 micron/sec velocity and 1 mN load. 

The Universal Nano-i-Micro Materials Tester (UNMT) has been developed to perform a variety of the common adhesion tests [2]. During any of them, it can simultaneously measure contact or surface electrical resistance displacement, deformation, or depth of penetration contact acoustic emission temperature forces in all three directions and digital video of the contact area. This report covers evaluation of the adhesion and delamination properties of coatings by the scratch test. 

Mar resistance of polymeric coatings depends on a number of factors, such as chemical components, molecular weight, crosslink material and its density, additives, processing procedure, etc. In addition, the tribological properties of coatings vary with the depth and age. A scratching test performed at the top surface at nano scale does not necessarily represent the performance in marring test at micro and submicron scales. An intensive study is needed before any conclusive statement can be made. 

The aim of the present chapter is to describe and to model the wear mechanisms of continuous fiher-reinforced polymer composites by using scratch tests, scanning electron microscopy, and finite element (FE) contact techniques applied to macro/micro-models, as well as a debonding algorithm developed. 

In addition to standard adhesion tests or failure tests that are explained in the previous chapters of this handbook, various types of special tests are also performed for specific purposes in industry or in scientific research. In this chapter, some special mechanical tests are treated, such as blister tests for membrane/adhesive/coating, tensile tests and shear tests for sealants and elastomeric/foam adhesives, and indentation tests and scratch tests for characterizing coating adhesion. Most of these are designed for testing macroscopic specimens in a macroscopic scale, but several micro- or nanometric test methods have recently been developed to measure mechanical properties of small specimens in a microscopic or nanometric scale. This chapter also introduces recently developed microscopic methods. 

Mohs hardness is a measure of the relative hardness and resistance to scratching between minerals. Other hardness scales rely on the ability to create an indentation into the tested mineral (such as the Rockwell, Vickers, and Brinell hardness - these are used mainly to determine hardness in metals and metal alloys). The scratch hardness is related to the breaking of the chemical bonds in the material, creation of micro fractures on the surface, or displacing atoms in the metals of the mineral. Generally, minerals with covalent bonds are the hardest while minerals with ionic, metallic, or van der Waals bonding are much softer. 

With this background several measuring methods are currently being discussed in the automotive and paint industry with the objective to obtain a clear characterization of the scratch resistance of clearcoats. Especially procedures that create a single scratch have recently been developed (micro or nano scratch method) [1-8], These methods are different from more practically oriented procedures that are based on relatively simple methods to fly to test or even come close to reality (e.g. car wash brush method). 

Specimens in a wide variety of shapes and dimensions (up to 200 mm) can be accommodated. For scratch-adhesion tests, various tool geometries and materials can be used, metal or ceramic ball or needle, diamond stylus or patented micro-blade. 

The multi-sensing technologj-, based on simultaneous high-resolution force and electrical and acoustic measurements, allows for ver> accurate determination of both delamination/ adhesion and scratch resistance of both thin and thick coatings. Using the test tools with higher contact area (or length), like micro-blade or ball, may allow for more repeatable results than those obtained with sharp styluses. 

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