Martensitic grades are basically Fe-Cr alloys with a higher carbon content than
ferritics which enables them to harden on cooling in air, oil or
Depending on grade and intended use, ductility is improved by
X12Cr13, 1.4006, 410
X15Cr13, 1.4024, 420
X20Cr13, 1.4021, 420A, 420J1
X30Cr13, 1.4028, 420B, 420J2
X39Cr13, 1.4031, 420
X46Cr13, 1.4034, 420C, 420HC
X65Cr13, 1.4037, 420D
X70CrMo15, 1.4109, 440A
X90CrMoV18, 1.4112, 440B
X105CrMo17, 1.4125, 440C
X3CrNiMo13-4, 1.4313, F6NM
X4CrNiMo16-5-1, 1.4418, S165M
X17CrNi16-2, 1.4057, 431
X12CrS13, 1.4006, 416
Typical applications for martensitic grades:
- cutting utensils
- surgical and dental Instruments
- fasteners, springs and ball bearings
- press plates
- steam and gas turbines
Precipitation hardening grades have higher alloying contents than martensitic grades.
They contain nickel, and in order to achieve hardening by aging
additions of copper, aluminium,
titanium, niobium and molybdenum.
Depending on chemical composition their microstructure after final
heat treatment is austenitic,
semi-austenitic or martensitic.
X5CrNiCuNb16-4, 1.4542, 630, 17-4PH
X7CrNiAl17-7, 1.4568, 631, 17-7PH
X5CrNiCu15-5, 1.4545, 15-5PH, AISI XM-12, S15500
15-7Mo, 1.4574, 632
X3CrNimOaL13-8-2, 1.4534, 13-8Mo, S13800
Typical applications for precipitation hardening grades:
- retaining rings, spring holders, springs
- chains, valves and gears
- aircraft parts
- pressure vessels and seals
High strength and hardness distinguish martensitic stainless steels
from the other stainless steel families.
After austenitizing cooling is performed in air, water or oil,
depending on steel grade. If the intended application requires a
high level of hardness (e.g. knives, HRC55),
only stress relief annealing will be performed. Normally
martensitic stainless steels are tempered in order
to acquire useful mechanical properties, i.e. a certain level of
toughness (A5 ≥ 15 %).
Nickel-martensitic steels are superior to traditional martensitic
grades regarding strength in combination with toughness.
Their microstructure contains stable austenite after hardening and
tempering which accounts for good toughness without drawbacks
concerning corrosion resistance.
Precipitation hardening stainless steels provide remarkable levels
of high strength and hardness in a
very wide range.
With the exception of the martensitic alloys (e.g. 1.4542) cold
formability is satisfactory.
Traditional martensitic steels with a carbon content > 0.20 %
are difficult to weld; assistance is advised. The hardenable
high-carbon grades are not suitable for welding.
Low-carbon nickel-martensitic grades have relatively good
Welding of precipitation hardened grades is possible, but depending
on grade some limitations might have to be regarded.
Corrosion resistance of martensitic stainless steels may vary
considerably depending on chemical composition (C, Cr, Mo),
surface finish and especially heat treatment. Smooth polished
surfaces experience higher resistance than rougher finishes.
In terms of heat treatment the hardened condition is more
favourable, since the elements promoting corrosion resistance are
in solution and therewith effective.
Tempering may lead to carbide precipitation which impairs corrosion
resistance. This is always the case for traditional martensitic
whereas nickel-martensitic grades with max 0.06 % carbon and 3-6 %
nickel (e.g. 1.4313 and 1.4418) do not sacrifice corrosion
resistance by tempering.
Corrosion resistance of precipitation hardening steels is higher
compared with heat treatable martensitic stainless steels ranking
between ferritic Cr and austenitic CrNi steels.