Martensitic stainless steel

Martensitic stainless steel - is a type of stainless steel alloy that has a body-centered tetragonal crystal structure (martensitic) in the hardened state. They are ferromagnetic, hardenable by heat treatment, and are generally resistant to corrosion only in relatively moderately aggressive environments.
Steel is a good choice for various applications due to its durability, strength, and resistance to corrosion. The composition and properties of martensitic steel give it advantages over other types of steel in various industrial functions. This steel is an ideal choice for the production of mechanical valves and instruments, turbine parts, medical instruments, and other applications and products.

Chromium content ranges from 10.5 to 18%, and carbon content may exceed 1.2%, although for materials commonly used for tubular goods and other oil and gas applications, carbon content is typically 0.020% or less. Small amounts of nickel may be added to improve corrosion resistance in some environments and to improve strength. Molybdenum and manganese may also be added in some martensitic grades.

The structures of these steels are tetragonal, body-centered, and they are classified in the "hard" ferromagnetic group. In the annealed condition, they have a tensile yield strength of about 275 MPa, so they are usually machined, cold-forged, or cold-worked in this condition. The strength obtained by heat treatment depends on the carbon content of the alloy. Increasing the carbon content increases the potential for strength and toughness, but reduces ductility and toughness. Higher grades of carbon are capable of being heat treated to a hardness of 60 HRC and above.

Optimum corrosion resistance is achieved in the heat-treated condition, i.e., quenched and tempered. Compared to austenitic and ferritic grades of stainless steel, martensitic stainless steels are less resistant to corrosion. Martensitic grades of stainless steel can be developed with the addition of nitrogen and nickel, but with a lower carbon content than traditional grades. Such steels have increased strength, weldability and corrosion resistance.