Knoop hardness testing is designed to assess the hardness property of fragile materials and relative samples of thin layers. The test is usually carried out using a pyramidal or cone-shaped diamond, by pressing the diamond against the surface of the material being tested. A small load of known weight is also added onto the pyramid, then the structure left for some time and the testing completed when the specified duration lapses. The final testing would require the aid of a microscope, to measure the miniature depression that was created by the indenter in the course of the hardness test.
Application and variability
The use of knoop hardness testers in assessment is vital in checking quality standards, especially when handling delicate materials, for example, ceramic. In contrast to the Vickers Test, knoop hardness testing is more accurate and the better option for assessing coated surfaces with extended elongations. The indenter used in Knoop testing has a penetrating ability found to be half the cavity derived when applying the Vickers test, meaning it has a higher sensitivity on facet conditions as compared to the latter. The knoop hardness test is a micro-hardness testing technique. It’s quicker, reliable, accurate and more sensitive. The loads to be used when testing should always be 1 or less than 1kgf. Therefore, to achieve desired results, it’s advisable that you ready the material’s surface for testing at all times by thoroughly polishing it.