410 vs 431 Stainless Steel: Martensitic Grades for Strength and Corrosion

Martensitic Family Overview

Martensitic stainless steels are iron-chromium alloys that transform to martensite when austenitized and rapidly cooled, allowing hardness levels comparable to hardened carbon steels. They are magnetic, can be tempered across a wide hardness range, and are selected where wear resistance, strength or hardness matter more than the ultimate corrosion resistance of austenitic grades. Grades 410 and 431 are two of the most widely used martensitic stainless steels, and the choice between them is driven by the balance of corrosion resistance, toughness and cost required by the application.

Chemical Composition Comparison

410 is a plain 12% chromium martensitic grade with no intentional nickel. 431 raises chromium and adds 1.25-2.50% nickel, which improves corrosion resistance and toughness, particularly in the hardened and tempered condition. Typical specification limits are shown below.

Element, %	410 (UNS S41000)	431 (UNS S43100)
C	0.08-0.15	0.20 max
Mn	1.00 max	1.00 max
P	0.040 max	0.040 max
S	0.030 max	0.030 max
Si	1.00 max	1.00 max
Cr	11.5-13.5	15.0-17.0
Ni	0.75 max	1.25-2.50

Reference standards: 410 per ASTM A240 and A276; 431 per ASTM A276 and EN 10088 grade 1.4057 (X17CrNi16-2). The EN equivalent of 410 is 1.4006 (X12Cr13).

Mechanical Properties and Hardness

Both grades are supplied annealed for machining and are hardened by oil or air quenching from the austenitizing temperature. The maximum practical hardness of both grades is about 45 HRC; higher tempering temperatures trade hardness for toughness and ductility. Representative values are shown below.

Property	410	431
Annealed hardness	217 HBW max	262 HBW max typical
Hardened hardness	up to about 45 HRC	up to about 45 HRC
Quenched and tempered condition, EN 10088-3	1.4006 +QT800: 800-950 MPa tensile, 600 MPa min yield, 12% min elongation	1.4057 +QT800: 800-950 MPa tensile, 600 MPa min yield, 14% min elongation

The +QT800 condition in EN 10088-3 means quenched and tempered to a minimum tensile strength of 800 MPa, a common specification for shafts and machine components in both grades.

Heat Treatment Differences

Hardening Response

410 is typically austenitized near 950-1010°C and quenched in oil or air, while 431 is austenitized near 980-1040°C to dissolve the higher alloy content. Both are tempered to the final hardness: low-temperature tempering near 150-370°C preserves maximum hardness for wear service, while tempering near 540-680°C restores toughness and ductility at lower hardness. Because both grades are air-hardenable in thin sections, welding without preheat can produce hard, crack-sensitive heat-affected zones, so preheating and post-weld tempering are standard practice.

Effect of Nickel in 431

The nickel addition in 431 stabilizes some austenite during quenching, refines the hardened structure, and improves toughness and corrosion resistance compared with 410. The practical result is that 431 components can be specified where parts need both high hardness and meaningful resistance to mild corrosive or marine environments, whereas 410 is limited to lightly corrosive service.

Application Selection Guide

Choose 410 When

Wear resistance and hardness dominate the design, for example valve seats, valve trim and pump components

Steam turbine blading and general engineering parts in lightly corrosive media

Cutlery and kitchen tools where economy matters

Cost-sensitive components that still require corrosion resistance better than carbon steel

Choose 431 When

Shafts, spindles and fasteners that need higher strength combined with better corrosion resistance than 410

Marine fittings, pump shafts and aircraft hardware exposed to moisture and chlorides

Applications where hardened strength and toughness must be retained with some corrosion margin

Welding and Machining Considerations

Both grades are weldable with matching martensitic filler metals such as ER410 or ER410NiMo, with preheat and post-weld heat treatment normally required to restore toughness and avoid cracking. Machining is best performed in the annealed condition; 431 is somewhat more difficult to machine than 410 because of its higher alloy content. Both grades grind and polish to a good finish and are supplied in bar, plate, sheet, strip, wire and forgings.

Frequently Asked Questions

1. What are the main differences in composition between 410 and 431?

410 contains 11.5-13.5% chromium with essentially no nickel, while 431 contains 15-17% chromium and 1.25-2.50% nickel. The higher chromium and the nickel addition give 431 better corrosion resistance and toughness in the hardened condition.

2. Why is nickel added to 431?

Nickel improves hardenability, refines the martensitic structure, and enhances toughness and corrosion resistance. It allows 431 to be used where a hardened component must also withstand mildly corrosive or marine environments.

3. How are these grades heat treated?

Both are austenitized, quenched in oil or air, and tempered. Low-temperature tempering near 150-370°C gives maximum hardness of about 45 HRC; tempering near 540-680°C lowers hardness but improves toughness. The exact cycle follows the applicable product standard and the required mechanical properties.

4. What are 410 and 431 typically used for?

410 is used for valve trim, steam turbine blades, cutlery, pump parts and wear-resistant components. 431 is used for shafts, spindles, fasteners, marine fittings and aerospace hardware where higher strength and better corrosion resistance are required.

5. Can 410 and 431 be welded?

Yes, both can be welded with martensitic filler metals such as ER410 or ER410NiMo, but preheating and post-weld heat treatment are normally required to prevent hard, crack-sensitive heat-affected zones and to restore toughness. For critical service, consult the applicable welding code and the material specification.