In the Vickers hardness test, a pyramid shaped indenter is pressed into the surface, usually under a load of 500 N. The Brinell hardness test generally uses a steel ball 10 mm diameter which is pressed into the surface under a load of 30 kN. The hardness can then be inferred from the width or area of the indentation or from its depth. The hardness of component surfaces is measured by indenting the surface with a small indenter made from a harder material. In Tribology Handbook (Second Edition), 1995 HARDNESS MEASUREMENT These are talc 1, gypsum 2, calcite 3, fluorite 4, apatite 5, feldspar 6, quartz 7, topaz 8, corundum 9, and diamond 10. Each material is allocated a number, 1 for the least hard material through to 10 for the hardest material.

It relates to the ability of each material to scratch ones that come before it on the scale. The Mohs’ scale of hardness is based on a group of ten materials of various hardness values, organized in order of increasing hardness. Very small indenters are used to measure the hardness of small particles. Vickers hardness is a ratio of the load expressed as kilograms force, of a square base diamond pyramid-shaped indenter, to the sloping area of the indentation formed. The ball diameter is 1, 2.5, 5, or 10 mm. The Brinell hardness number is a number proportional to the load or test force of a hard steel ball to the calculated curved area of the indentation formed. Hardness can be defined as the resistance of a material to an applied pressure or force. David Mills, in Pneumatic Conveying Design Guide (Third Edition), 2016 Hardness

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