Austenitic vs Martensitic Stainless Steel: Composition, Grades, and Key Differences
Stainless steel is available in many grades, each of which is designed for unique applications. Austenitic and martensitic grades are two categories of stainless steel that are commonly encountered, but their properties are nearly opposites. As such, it is important to learn the differences between these types of stainless steels when choosing materials for a specific application. The terms austenite and martensite actually refer to two very different metallurgical phases- austenite is a FCC (face-centered cubic) form of iron, and martensite is a hardened structure formed from rapid cooling. These two phases are the reason that austenitic and martensitic stainless steels have very different properties in their chemistry, strength, and corrosion resistance. In this blog, we will consider the composition and grades for each type while discussing their properties, and in the end, we will directly compare austenitic and martensitic stainless steel grades correspondingly. In the end, it will be clear when to use austenitic stainless steel and when to use martensitic stainless steel.
What Is Stainless Steel Made Of?
Austenitic stainless steel is known for its iron-chromium alloy, which typically has high chromium (~16-26%) and nickel (~6-22%) properties. Nickel is the alloying element that stabilizes the austenite phase, meaning under all temperatures (including room temperature), the austenitic steel will remain in the austenite phase. In addition to the Ni content, the grade steel may also have small amounts of other elements like manganese or nitrogen, which will also contribute to recovering the austenite phase under all temperatures. Because of the FCC microstructure, austenitic steel is typically thought of as the most ductile, or what is called the least amount safety factor when analyzed under ultimate stress when compared to the more common body-centered cubic or BCC microstructure found in most steels.
Key Properties of Austenitic Stainless Steel
Austenitic stainless steel composition typically includes ≥16% Cr with Ni (plus optional Mo/N, Mn), stabilizing the FCC austenite phase. This drives the properties below.
Property | What drives it (metallurgy) | Practical impact |
Corrosion resistance | ≥16% chromium forms a stable passive oxide film; Mo (e.g., 316) improves pitting resistance | Resists rusting in most environments, including many acidic and marine conditions |
Ductility & toughness | FCC austenite phase remains stable at room temperature | Can be bent, deep-drawn, or formed into complex shapes without cracking |
Strength & work-hardening | Cold work raises dislocation density in austenite | Moderate yield strength in annealed state; can be significantly strengthened by cold-working |
Weldability | Low carbon (L-grades) and metallurgical stability reduce sensitization | Generally easy to weld; good joint integrity without brittle fracture when procedures are followed |
Magnetism | Austenite (FCC) is essentially non-magnetic in the annealed condition | Suitable for applications needing low magnetic permeability |
Service temperature | Cr/Ni balance (and Mo/Ti where applicable) | Good performance from cryogenic to elevated temps; specific heat-resistant grades available |
Common Austenitic Stainless Steel Grades (200 & 300 Series)
| Series | Grade | Typical composition (approx.) | Hallmark traits | Typical uses |
| 300 | 304 (18/8) | ~18% Cr, ~8% Ni | General-purpose; excellent corrosion resistance; easy fabrication | Process equipment, piping, architectural, consumer goods |
| 300 | 316 | ~17–18% Cr, ~10–12% Ni, ~2% Mo | Enhanced chloride/pitting resistance vs 304 | Marine hardware, chemical process, food & pharma |
| 300 | 310 | Higher Cr+Ni than 304 | Superior oxidation resistance at high temperature | Furnaces, heat exchangers, high-temp fixtures |
| 300 | 321 | Similar to 304 + Ti stabilization | Better resistance to intergranular attack at elevated temps | Exhaust systems, thermal process equipment |
| 200 | 201/202 | Cr-Ni with Mn/N partially replacing Ni | Reduced-Ni option; higher yield strength vs comparable 300-series | Structural components, appliances, formed parts |
All listed grades share the austenitic (FCC) structure. Selection should consider the environment (corrosion/chlorides), forming/welding needs, and required strength.
Applications of Austenitic Stainless Steel (304, 316 and related grades)
Typical applications of austenitic stainless steel include:
- Food & beverage processing: conveyors, mixers, kettles, tanks, CIP lines, and kitchen utensils; resists food acids and frequent cleaning
- Chemical & pharmaceutical plants: tanks, piping, valves, heat exchangers; easy clean & sterile, resistant to many chemicals
- Medical & lab equipment: non-magnetic components for imaging scanners, surgical instruments, trays, benches, autoclave-safe fixtures
- Marine & coastal hardware: 316ST for docks, fasteners, pumps, & fittings exposed to chlorides and saltwater spray
- Water treatment: clarifier, UV housings, filter frames, RO skids, chemical dosing lines
- Oil & gas & energy applications: lines for condensate process, scrubbers, flue gas components, LNG cryogenic service (specify austenitic grades)
- Architecture & construction: façades, guard rails, anchors, cladding, structural elements, applications that must endure weathering and appearance retention
- Food storage and transport: food grade silos, IBC’s, tankers, pipe-work, etc for dairy and brewery
- HVAC & refrigeration applications: duct, duct housing, fasteners, supports, etc where corrosion control is mandatory
- General fabrication: sheet, coil, plate, tube, bar, fasteners, flanges where high formability, cleanability and toughness are needed.
What is Martensitic Stainless Steel?
Martensitic stainless steels have a different balance of elements formulated for hardenability with heat treatment. They usually contain moderate levels of chromium (approximately 11.5–18%) and higher amounts of carbon (~0.1–1.2%), and very low levels of nickel. This chemistry is the key point of distinction; the higher carbon in martensitic stainless steels allows it to form the very hard phase martensite upon appropriate heat treatment. Martensitic steels form in the austenitic state at high temperatures in the same way that all steels do, but once cooled sufficiently fast, the steel undergoes the transformation into martensite, which exists in a supersaturated body-centered tetragonal (BCT) crystal structure that is highly strained and hard. Note that martensitic stainless steels must be hardened and tempered to realize the properties; as-annealed (soft) martensitic steel lacks the exceptional strength typically associated with martensitic stainless steels. The heat treatment for martensitic alloys is austenitizing the steel, quenching to permit transformation to martensite, and applying a tempering step to reduce fragility.
Key Properties of Martensitic Stainless Steel
| Property | What drives it (metallurgy) | Practical impact |
| Strength & hardness | Quench-and-temper martensitic microstructure; higher C content | Very high tensile strength and wear resistance; tool-steel-like hardness in some grades |
| Ductility & toughness | High hardness reduces plasticity | Lower impact resistance than austenitic; tempering required to reduce brittleness |
| Corrosion resistance | 11.5–18% Cr but little/no Ni; carbide formation can tie up Cr | Moderate corrosion resistance; suitable for mildly corrosive/oxidizing environments |
| Weldability | Hard, crack-sensitive HAZ; higher C | Preheat and post-weld tempering often required to control cracking |
| Formability | Limited due to hardness and strain sensitivity | Not suited to deep drawing/heavy cold work; risk of cracking in hardened state |
| Magnetism | BCT martensite is ferromagnetic | Magnetic in annealed and hardened conditions |
Common Martensitic Stainless Steel Grades (400 Series)
Grade | Typical composition (approx.) | Typical hardness range* | Hallmark traits | Typical uses |
410 | ~12% Cr, ~0.10% C | up to ~HRC 40 | Baseline martensitic; balanced strength, fair corrosion resistance; easier to machine than higher-C grades | Fasteners, pump shafts, turbine blades, general components |
420 | ~13% Cr, ~0.30% C | mid-40s HRC after temper | Higher hardness than 410; good edge retention; food/medical compatible when polished and passivated | Cutlery, surgical instruments, precision tools |
440C | ~17% Cr, ~1.0% C | HRC 55+ when fully hardened | Highest hardness among standard stainless; excellent wear resistance; lower toughness | Ball bearings, knife blades, chisels, high-wear parts |
416 (free-machining) | ~13% Cr, S added | ~HRC 35–40 | Sulfur improves machinability; moderate strength | Screw-machine parts, fittings |
17-4 PH (630) | ~16–17% Cr, ~4% Ni, Cu + Nb (PH) | up to ~HRC 44 (condition dependent) | Precipitation-hardened martensitic; high strength with good toughness | Aerospace fittings, shafts, valves, structural hardware |
*Actual hardness depends on heat treatment (austenitize, quench, temper) and section size.
Applications of Martensitic Stainless Steel
Typical uses of martensitic stainless steel include:
- Knife blades and cutlery: 420 and similar grades properly heat treated to produce a sharp and wear resistant edge; table knives, kitchen knives, and industrial blades
- Surgical and medical devices: scalpel blades, scissors, and clamps; high hardness gives better edge retention in wear resistant
- Valves, shafts, and pumps: machinery components with high friction and load; 410 is commonly used for these in moderate use environments
- Bearings and springs: rolling or static bearings and springs typically require 420/440 grades, where high strength and fatigue resistance are significant
- Aerospace hardware: critical component hardware used for landing gear and actuation that must be assembly strong after heat treated
- Automotive component parts: elements of engines and exhaust that would be beneficial from quench and temper to develop strength and wear resistance
- Hand tools and power tools: inserts for screwdrivers, cutting elements in shear, cutting tools needing long edge retention and general wear resistance
- General wear parts: general use parts like pins, or fasteners, dies or fixtures. Regardless of grade if hardness and mechanical load capacity is greater than highest resistance to corrosion
Selecting the Right Type of Steel for Your Needs
When choosing between an austenitic or martensitic stainless steel, consider the service conditions and priorities:
- If you want maximum corrosion resistance, ease of fabrication, or want a non-magnetic alloy, use austenitic stainless steel. Stainless steel grades like 304 or 316 are preferred for wet and/or acidic environments, food-grade or medical equipment, or anywhere rust prevention is paramount.
- If you need extreme strength, wear resistance, or the ability to maintain a sharp edge in a fairly mild environment, the desired martensitic stainless steel is most appropriate. Martensitic steels may require protective coatings or significant upkeep in corrosive environments to avoid staining.
Often the final decision may involve cost and availability, but the project job specification is a primary factor. Austenitic steels may have a slightly higher price (due to the nickel content) but provide wider use characteristics. Martensitic steels are selected for specific high-hardness applications.
Stellar Alloys provides several grades of both austenitic and martensitic stainless steels. Our technical staff can help you review your project’s requirements and recommend the best grade for your application that will provide the right combination of corrosion resistance, strength, and toughness. You now have an understanding of the primary differences presented for your consideration to either make an informed choice or discuss your project with us to choose the stainless steel that will perform according to your proposed service conditions.
FAQs about Austenite and Martensite Steel
Martensitic stainless steels have higher hardness, strength and brittleness than austenitic stainless steels, but with that higher strength comes a cost: martensitic stainless steels are not as good at resisting corrosion, so they are more prone to rust in certain conditions. Martensitic steels are also much harder to form.
Up to a heating rate of about 10°C/s, the reverse transformation of α′ martensite to γ austenite occurs through diffusion, whereas above 10°C/s, the transformation occurs via a diffusionless shear mechanism.
Hydrogen increases the potential for hydrogen-induced cold cracking. However, as a general rule, martensitic steels can be welded without concern for cracking in the HAZ if proper precautions are taken.
Products
LOCATIONS
