The Rockwell hardness test measures materials hardness based on the net increase in depth of impression as a load is applied. Hardness numbers have no units, and the higher the number in each of the scales, the harder the material.
In the Rockwell method of hardness testing, the depth of penetration of an indenter under certain arbitrary test conditions is determined.
Hardness is defined as resistance to local penetration, scratching, machining, wear or abrasion, and yielding. The multiplicity of definitions, and corresponding multiplicity of hardness measuring instruments, together with the lack of a fundamental definition indicate that hardness may not be a fundamental materials property but rather a composite one including yield strength, work hardening, true tensile strength, modulus of elasticity, and others.
Vickers hardness is a measure of materials hardness calculated from the size of an impression produced under load by a pyramid-shaped diamond indenter. The diamond pyramid hardness test permits the establishment of a continuous scale of comparable numbers that accurately reflect the wide range of hardness found in steels.
The Vickers test is reliable for measuring metals hardness and is also used on ceramic materials.
The Vickers indenter is a 136° square-based diamond cone. The indenter’s diamond material has an advantage in that it does not deform over time and use. The impression left by the Vickers penetrator is a dark square on a light background.
The correct Vickers designation is a number followed by HV (Hardness Vickers).
The advantages of the Vickers hardness test include accurate readings and just one type of indenter being used for all types of metals and surface treatments.
Although adaptable and precise for testing the softest and hardest materials under varying loads, the Vickers machine is a standing unit and more expensive than a Brinell or a Rockwell.
