Hardness

Types of Hardness Measurements

• There are three main types of hardness measurements: scratch, indentation, and rebound.
• Scratch hardness measures the resistance to fracture or permanent plastic deformation due to friction.
• Indentation hardness measures the resistance to material deformation under a constant compression load.
• Rebound hardness measures the height of the bounce of a diamond-tipped hammer dropped onto a material.

Scratch Hardness

• Scratch hardness is determined by the force necessary to cut through a film to the substrate.
• Mohs scale is commonly used to measure scratch hardness in mineralogy.
• Sclerometer and pocket hardness tester are tools used to measure scratch hardness.
• The pocket hardness tester uses a weight and markings to apply a known pressure.
• Scratch hardness is based on the principle that a harder material will scratch a softer material.

Indentation Hardness

• Indentation hardness tests are primarily used in engineering and metallurgy.
• Common indentation hardness scales include Rockwell, Vickers, Shore, and Brinell.
• The tests measure the critical dimensions of an indentation left by a loaded indenter.
• Indentation hardness is a measure of resistance to material deformation under compression.
• Different materials have different indentation hardness values.

Rebound Hardness

• Rebound hardness measures the height of the bounce of a diamond-tipped hammer.
• It is related to elasticity and is measured using a scleroscope.
• Leeb rebound hardness test and Bennett hardness scale are two scales for rebound hardness.
• Ultrasonic Contact Impedance (UCI) method determines hardness by measuring the frequency of an oscillating rod.
• Rebound hardness is used to assess the elastic properties of a material.

Hardening Processes

• There are five hardening processes: Hall-Petch strengthening, work hardening, solid solution strengthening, precipitation hardening, and martensitic transformation.
• Hardening processes increase the hardness of a material.
• Hall-Petch strengthening is based on the relationship between hardness and grain size.
• Work hardening occurs when a material is plastically deformed.
• Different hardening processes have different effects on the material's microstructure.

Hardness Mentions

Hardness Data Sources