There are two principal methods of testing the hardness of a material – scratch testing and indentation testing. Indentation testing can only be used on materials that undergo plastic deformation such as metals and thermoplastic polymers. Scratch testing is therefore used for brittle materials such as ceramics. The hardness of a material can be determined based on Moh’s scale of hardness, which ranks a material based on a list of standard materials with known hardness. The hardness of the material is ranked on the scale between the material it just scratches and the material that it fails to scratch. There are a number of different methods of testing the hardness of a material through indentation. The three most commonly used are the Brinell test, the Vicker’s Diamond test, and the Rockwell test. All three methods involve indentation of the material. The hardness is calculated by measuring the force applied and comparing this to some geometrical aspect of the indentation such as the surface area or depth. Vickers Brinell Rockwell (diamond) (ball) (cone) Hold your mouse over the imageto see the indentations that result from the three different tests. When hardness indentation testing is done on an actual component it is often necessary to blend (grind) out the indentation to remove the stress concentration it producesScratch testing
Moh's Scale of hardnessIndentation testing
FAQs
What is the point of hardness testing? ›
What is the definition of hardness testing? The application of hardness testing enables you to evaluate a material's properties, such as strength, ductility and wear resistance, and so helps you determine whether a material or material treatment is suitable for the purpose you require.
What are the measurements of hardness? ›Measures. There are three main types of hardness measurements: scratch, indentation, and rebound. Within each of these classes of measurement there are individual measurement scales. For practical reasons conversion tables are used to convert between one scale and another.
How is the hardness test completed? ›The three most commonly used are the Brinell test, the Vicker's Diamond test, and the Rockwell test. All three methods involve indentation of the material. The hardness is calculated by measuring the force applied and comparing this to some geometrical aspect of the indentation such as the surface area or depth.
What is the most common method of hardness testing? ›Common hardness testing types include Rockwell (indentation depth or un-recovered indentation), Knoop/Vickers, and Brinell (area of indentation). Rockwell testing is the most commonly used method by virtue of the quick results generated and is typically used on metals and alloys.
Which hardness test is more accurate? ›The most commonly applied and generally accurate hardness test is the Rockwell test, as defined in ASTM E-18.
What is the formula for material hardness? ›HV = 1.854(F/D2), with F being the applied load (measured in kilograms-force) and D2 the area of the indentation (measured in square millimetres). The applied load is usually specified when HV is cited. The Vickers test is reliable for measuring the hardness of metals, and also used on ceramic materials.
What is 7 hardness? ›The minerals are listed from hardest to softest with their hardness scale number as follows: Diamond, 10; Corundum, 9; Topaz, 8; Quartz, 7; Orthoclase, 6; Apatite, 5; Flourite, 4; Calcite, 3; Gypsum, 2; and Talc, 1.
What are the 4 units of hardness? ›Different Hardness Units
For scratch, indentation, and rebound hardness, the measurement methods vary (e.g. Brinell, Rockwell, Knoop, Leeb, and Meyer).
1. Tungsten (1960–2450 MPa) Tungsten is one of the hardest metals you will find in nature. Also known as Wolfram, the rare chemical element exhibits a high density (19.25 g/cm3) as well as a high melting point (3422 °C/ 6192 °F).
What is the hardness of a diamond? ›One the Mohs scale of relative hardness, a diamond is rated as 10. This means that it is the hardest mineral known to man.
What size sample is used for hardness testing? ›
Standard Specimen Size for Micro Hardness Testing (L= 30mm, W= T= 6mm)
How to measure material hardness? ›The surface area of the indentation is the measure of hardness HB of the material. The round impression is measured using a low-power microscope in millimeters. This round indent produced is measured to calculate material hardness according to the formula. It is generally referred to as Brinell hardness number.
How to calculate Rockwell hardness? ›Calculate the Rockwell hardness value: Use the following formula to calculate the Rockwell hardness value:HR = N – (d / D)where HR is the Rockwell hardness value, N is the load applied (in kgf), d is the depth of the indentation (in mm), and D is the diameter of the ball or the width of the diamond cone (in mm).
Why is it important to test the hardness of water? ›When hard water is heated, such as in a home water heater, solid deposits of calcium carbonate can form. This scale can reduce the life of equipment, raise the costs of heating the water, lower the efficiency of electric water heaters, and clog pipes.
Why is it important to know the hardness? ›Understanding the hardness of a metal is vital to determine how long it will last in various settings. For example, a harder material will generally be able to withstand wear for much longer. If you know the hardness, you can also get a better idea of how likely a material is to fail under certain circ*mstances.
What is the significance of hardness determination? ›Hardness is the property of a material that allows it to resist permanent distortion, penetration, indentation, and scratching. Therefore, hardness is important from an engineering point of view because resistance to wear by either friction or erosion from steam, oil, and water generally increases with hardness.
Why do we do total hardness test? ›The total hardness test can be used to measure water hardness. Water hardness is caused by the presence of alkaline earths, primarily calcium and magnesium. Total hardness is measured as the sum of all calcium and magnesium ions.