PH 13-8 Mo is a martensitic precipitation-hardening stainless steel which is desired for its corrosion resistance, superior toughness, remarkable strength, and high hardness. 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 micro-cleanliness 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.

PH 13-8 Mo 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 17-4 PH alloy, it requires only a one-step heat treatment 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.