Defining Martensitic Stainless Steel
The term “martensitic” is derived from the microstructure formed during heat treatment, called martensite. This provides the exceptional properties constituting martensitic stainless.
400 series grades are martensitic and can be supplied either annealed or quenched and tempered to a specific tensile range. Those supplied in the annealed condition can be heat treated for enhanced strength and hardness.
Applications of Martensitic Stainless Steel
Martensitics are used in various industries that require hardness, strength and wear-resistance, such as the following:
- Cutlery and Tools: Knives, scissors, and medical tools due to its hardness and sharp edge retention. E.g. 420/440C
- Industrial Equipment: Gears, valves, pumps, and shafts benefit from its strength and durability. E.g. 431/1.4418
- Aerospace and Automotive: Engine components and structural parts rely on its high strength-to-weight ratio. E.g. 431/420
- Energy Sector: Used in turbines and components exposed to moderate corrosion and high wear. E.g. 431/420/410 QDT
Composition of Martensitic steel
Martensitic stainless steel is characterised by its chromium content; typically, 11-18% of its composition. Other elements include carbon, which contributes to its hardness and strength, and small amounts of alloying elements, such as molybdenum, sulphur, nickel or manganese, which can be added to provide different properties.
Martensitic Steel Grades
Bird Stainless stock a variety of different 400 series martensitic stainless grades: 410, 420, 416, 440B, 440C, 431 & 1.4418.
410: low carbon (0.08-0.15%), general-purpose martensitic.
420: high carbon (0.15-0.20%) version of 410 with the addition of Sulphur for enhanced machinability.
416: high sulphur (0.15-0.35%) version of 410 (0.05% max.) which provides higher machinability. As a result, this martensitic is known as the free machining grade of the 400 series.
440B: high carbon (0.75-0.95%) martensitic that is easily machined for high hardness (hardenability up to 58 HRC).
440C: very high carbon content (0.95-0.12%) for the highest hardness (hardenability up to 60 HRC) and wear resistance.
431: high chromium (15.0-18.0%) and low nickel (1.5-3.0%) martensitic with improved strength and corrosion resistance.
1.4418: high strength, low carbon (<0.06%) martensitic.
The diagram below details the varying ultimate tensile strengths (UTS) of the martensitic grades stocked by Bird Stainless:
What’s the Difference Between Martensitic and Austenitic Stainless Steel?
Martensitic stainless steel differs from austenitic stainless steel in composition, properties and applications. Martensitic grades are known for their high strength, hardness and moderate corrosion resistance. In contrast, austenitics have higher chromium and nickel contents for superior corrosion resistance but lack the hardness of martensitics.
Bird Stainless also carry Precipitation Hardening Martensitics which are a combination of the two, displaying characteristics of both martensitic and austenitic steels.
Precipitation Hardening Martensitic Stainless Steel
Other common martensitic grades are Precipitation Hardening Martensitics such as 17/4PH and FV520B, which display characteristics of both austenitic and martensitic steels. These grades are aged hardened to achieve structured mechanical properties. The temperature at which these grades are aged provides different heat-treated conditions with specific properties.
17/4PH: high chromium (15.0-17.0%) steel that combines high strength, toughness and corrosion resistance.
FV520B: low carbon (<0.07%) steel, similar to 17/4PH in terms of properties.
Conclusion
Martensitic stainless steel is a versatile material that offers a unique combination of strength, hardness, and moderate corrosion resistance. Whether you’re designing tools, industrial machinery, or medical devices, martensitic grades provide a reliable solution for demanding applications. Partnering with a trusted stainless steel stockholder ensures you get the right material for your specific requirement, with fast quotes and delivery available from Bird Stainless.