hardnesstesting

Hardness testing is a set of material characterization methods that measure a material's resistance to localized plastic deformation, typically by pressing an indenter into the surface under a defined load. The resulting hardness value aids material comparison, qualification, and process control.

Common methods include Brinell, Rockwell, Vickers, and Knoop. Brinell uses a hardened ball and reports HB; Rockwell uses a diamond cone or steel ball with a minor and major load to yield scales such as HRC and HRB; Vickers uses a diamond pyramid to produce HV; Knoop uses an elongated diamond to produce HK. Microhardness uses lower loads for small features or thin films, producing HV or HK values.

Tests are conducted on flat, prepared surfaces with specified dwell times. Standards such as ISO 6507 and ASTM E10 cover Brinell, ASTM E18 covers Rockwell, ASTM E384 covers Vickers, and related microhardness standards guide apparatus, loads, and measurements; results are typically traceable to reference blocks.

Interpretation: hardness often correlates with strength and wear resistance in metals but does not directly measure tensile strength or toughness. Variations in surface finish, microstructure, temperature, and indentation geometry affect results; hence hardness measurements are used comparatively or alongside other material properties in quality control and material selection.