ATI 13-8™ alloy (UNS S13800) is a martensitic precipitation-hardening stainless steel that has excellent strength, high hardness, superior toughness, and good corrosion resistance. Good transverse toughness properties are achieved by tight chemical composition control, low carbon content, and vacuum melting. The alloy is produced by vacuum induction melting (VIM) followed by electro-slag remelting (ESR). This melt practice promotes excellent macro- and microcleanliness, and tight compositional control. The strengthening mechanism (precipitation hardening in a martensitic matrix) makes it possible to achieve uniform strengthening in heavy sections. Strength and ductility levels can be tailored to the application by varying the aging temperature. Typical applications are large airframe structural components, injection molding equipment and slide gates to control water flow.

The S13800 alloy is martensitic in structure in the solution annealed condition and is further strengthened by a relatively low temperature heat treatment, which precipitates a strengthening phase in the alloy. Like the S17400 alloy, the S13800 alloy requires only a simple heat treatment, a one step process conducted at a temperature in the range 950°F (510°C) to 1150°F (620°C) depending on the combination of strength and toughness desired. A wide range of properties can be produced by this one step heat treatment. Heat treatment at about 950°F (510°C) produces the highest strength.