HARDNESS

Hardness is the resistance a material exhibits against penetration. Properties such as shock resistance, wear resistance, scratch resistance, and friction coefficient are all directly related to a material’s hardness. Numerous hardness tests are tailored to different material families or specific requirements, each having its own unit system. These tests fall into several major categories:

Macroindentation tests (Vickers hardness, Rockwell hardness, Knoop hardness, etc.)
Tribological/scratch tests (Mohs scale, etc.)
Pendulum damping tests (Persoz hardness, König hardness)

Macroindentation Tests
Macro-indentation tests measure the imprint left by an indenter (typically a pyramidal diamond) under a specified load dropped from a fixed height onto a sample of set dimensions. The shape and weight of the indenter, the height from which it falls, and the dimensions of the sample are specific to each test.

Tribological/Scratch Tests

The most well-known and widely used tribological test is the Mohs scale, which determines the hardness of minerals. This scale comprises ten degrees ranging from the softest (talc) to the hardest (diamond), classifying minerals by comparison according to their ability to scratch one another. Diamond scratches corundum, which scratches topaz, which in turn scratches quartz, and so forth.

Pendulum Damping Tests

Pendulum damping tests are favoured for measuring the hardness of coatings and surface treatments, although they can also be applied directly to materials. The pivot feet of the pendulum rest on a sample of specified dimensions. The pendulum is released from a defined angle (6° or 12°). A softer material will absorb the pendulum’s amplitude more quickly than a harder material.