Zwischenhärte

Zwischenhärte is a term used in German-language materials science to describe an intermediate hardness value that exists between two reference hardness levels or within a hardness gradient. The term does not designate a defined material constant in international standards; instead it functions as a descriptive label for a region or point in a hardness profile that is not as soft as a substrate nor as hard as a coating or surface layer, for example, or as the characteristic value found in a graded material.

Measurement and characterization of Zwischenhärte typically relies on hardness profiling across a cross section. Techniques such as microhardness testing (Vickers, Knoop) or nanoindentation are used to create hardness versus depth maps. The Zwischenhärte value is then used to denote a position in the profile where hardness lies between two distinct regions or indicates the presence of a gradual transition.

Interpretation and applications occur mainly in surface engineering, coatings, and functionally graded materials. A transition layer or gradient region may exhibit Zwischenhärte, reflecting changes in composition, microstructure, or residual stress that influence wear resistance and adhesion. Because hardness depends on test scale, load, and indenter geometry, Zwischenhärte is not directly comparable across studies or methods; it is primarily descriptive and used to discuss material behavior in gradient or coated systems.

Limitations and terminology note that Zwischenhärte is not standardized. When communicating results, it is important to specify the testing method, scale, and context to avoid misinterpretation.

See also: hardness, microhardness testing, nanoindentation, hardness gradient, coatings and surface engineering.