Vickers Hardness
Vickers hardness is a unit of measurement for the hardness of various materials. The Vickers test method is also used to determine the hardness of knife blades. In physics, hardness describes the mechanical resistance a material offers against mechanical penetration by another object.
The hardness of the material is an important indicator for its response to wear and tear: Hard materials are less susceptible to being damaged or worn out with constant use than soft materials. However, a high hardness grade also has its disadvantages, because hard materials tend to be more brittle and thus easier to break than soft materials. There are several different methods to determine the hardness of materials, including the Vickers hardness test (HV).
It yields extremely precise measurements and is used to test the hardness of particularly hard or thin items for which other testing methods (e.g. Brinell or Rockwell) would be much less exact. Like other tests, the Vickers hardness test measures the hardness of an object by bringing a standardized indenter in contact with the test object, applying standardized pressure for a precisely determined period (between ten and 15 seconds). Afterwards, the indentation is measured and the ratio between the indentation and the applied pressure calculated with the help of the formula. The resulting value is the Vickers hardness (HV). The Vickers method uses a diamond-shaped indenter in the form of a square based pyramid. Different materials call for indenters of different sizes. Measurements are taken in the macro, low-load and micro ranges.
The measurement is expressed with an abbreviation comprising the hardness value (e.g. 440), the test method (Vickers hardness test, HV), the testing strength in kilopond (about 30) and the test time. If the test time is outside of the standard range of ten to 15 seconds, it is stated as well (approximately 20 seconds). In our example, the Vickers measurement would be 440HV30/20.