hardenable

Hardenable is an adjective used in materials science to describe a substance that can be hardened through heat treatment or other processes. In metallurgy, the term is most often applied to iron-carbon alloys, particularly steels and some cast irons, that can develop a substantially harder microstructure, such as martensite, when properly quenched and tempered.

Hardenability refers to the material's tendency to form hard phases with depth from the surface when quenched. It is distinct from hardness, which is a measure of a material's resistance to indentation at a given location. The depth and uniformity of hardness depend on alloy composition, carbon content, grain size, quench rate, and heat-treatment parameters. Common alloying elements that increase hardenability include chromium, nickel, molybdenum, vanadium, and manganese.

A practical assessment is the Jominy end-quench test, which profiles hardness along a sample to indicate how deeply a given alloy can be hardened. Designers use hardenability to select suitable steels for a given cross-section and quenching method, balancing strength, toughness, and distortion risk.

In practice, many steels are classified as hardenable or non-hardenable. Plain carbon steels with low carbon content are often considered non-hardenable in thick sections, whereas alloyed steels with adequate alloying elements are considered hardenable. The term can also apply to other materials that can be made harder by post-processing, though its use is most established in steel metallurgy.