As a stainless steel that can adjust material properties through heat treatment, martensitic stainless steel is a hardenable stainless steel. The characteristics of martensitic stainless steel are high hardness, strong mechanical and corrosion resistance properties. These characteristics determine that martensitic stainless steels must have two basic conditions. First, there must exist an austenite phase region in the equilibrium phase diagram. Second, to enable martensitic stainless steels to form a passive film with strong corrosion resistance, martensitic stainless steels must contain more than 10.5% chromium.

According to the differences in alloying elements in martensitic stainless steels, martensitic stainless steels can be divided into chromium martensitic stainless steels and chromium-nickel martensitic stainless steels. Chromium martensitic stainless steels can be further divided into low-carbon, medium-carbon and high-carbon types. Martensitic stainless steels have a body-centered tetragonal crystal structure in the quenched state, with ferromagnetic properties. They have corrosion resistance in relatively weak corrosive environments. The chromium content in martensitic stainless steels can be up to 18%, and the carbon content can exceed 1.2%.

To enhance the corrosion resistance of martensitic stainless steels and the sharpness of blades made from them, excess carbides can exist in the microstructure. Small additions of niobium, silicon, tungsten and vanadium can be made to optimize the tempering effect after quenching. Nickel-containing martensitic stainless steels improve the corrosion resistance of chromium martensitic stainless steels in some environments and enhance the toughness. Carbon is an indispensable important element in martensitic stainless steels. It enables the formation of a phase region between the iron-chromium binary alloy elements, which also affects the hardness of martensitic stainless steels in the quenched state.Experiments show that the hardness of a 0.1% carbon martensitic stainless steel is about 35 HRC, while a 0.5% carbon martensitic stainless steel can have a hardness higher than 60 HRC. However, further increasing the carbon content will not significantly increase the hardness.

There are 18 martensitic stainless steel grades listed in domestic standards, mainly of 13% chromium and 17% chromium types.

Due to their excellent mechanical properties, moderate corrosion resistance, and good heat resistance below 650°C, martensitic stainless steels have been widely used in various industrial fields. Low and medium carbon martensitic stainless steels, such as 1G13 and its modified grades, are mainly used in steam turbines, jet engines, gas turbines, etc. They are also widely used in the petroleum and petrochemical industries.

Slightly higher carbon steels like 2G13 are mainly used for cutting tools, valve parts, gears, pulleys, switch shafts and other mechanical parts and bars. High carbon martensitic stainless steels such as 9G18Mo are used for cutting tools, bearings, surgical and dental instruments, scissors, springs, valves, shafts, cams, etc.

The tempering brittleness temperature range of martensitic stainless steels is 425-565°C. Tempering the steel in this temperature range can significantly reduce the impact toughness. For impact resistance critical components, this tempering temperature should be avoided and application in this temperature range should also be avoided.