Difference between austenitic and martensitic stainless steel

What is the difference between austenitic and martensitic stainless steel?

The classification of stainless steel is dependent on its crystalline microstructure. The chemical composition of Stainless steel contains iron. Along with iron, stainless steels also have additions of chromium as well as other elements (nickel, chromium, or molybdenum) in its alloy. The minimum content of chromium in stainless steel is 11%, which keeps it from rusting. The use of chromium in the alloy is what also makes it immune to heat. The microstructure of each class of stainless steel varies with the inclusion of different elements in its chemistry in varying quantities. For instance, the austenite microstructure, which is also in the study of crystallinity of metals is referred to as a face-centered cubic structure. The FCC microstructure is the result of the addition of nickel, nitrogen, or manganese to the alloy. This sort of elemental composition also improves the corrosion resistance properties and mechanical properties of the alloy. On the other hand, the microstructure of martensitic stainless steel is BCT, or what is referred to as body-centered tetragonal. Being a highly strained structure, the chemical composition of the metal has been supersaturated with carbon. Another distinguishing characteristic for both these classes of stainless steels is their property of hardenability, which could be influenced as a result of heat. Austenitic stainless steel alloys cannot be hardened with the use of heat treatment. This is because the microstructure of an austenite variety of stainless steel remains the same i.e. FCC, despite a change in its environmental temperatures. Hence, heat treatments do not work on such alloys. On the other hand, martensitic stainless steel could be easily hardened by the use of heat treatment. Yet, it is this property that makes the alloy less resilient to corrosion as compared to the austenitic class of stainless steel.

While austenitic stainless steels tend to have very high ductility in terms of formability, those alloys belonging to the martensitic type tend to illustrate very high hardness. The hardness of these steels is on account of the supersaturated carbon content in the chemistry of their alloys. And because they are hard, martensitic classes also tend to be brittle in quite a few instances. So, in applications that demand high toughness or tough surface areas, the use of martensitic stainless steel is a viable option. Since the Austenitic variety of stainless steel is highly ductile, manufacturers can use them to produce several shapes and forms. Therefore, the manufacture of pipes, bars, hollow bars, sheets, coils, plates, fasteners, fittings, and flanges are much easier. In fact, austenitic stainless steels are the most utilized category across several industries. The content of chromium in martensitic steels is lower than their austenitic counterparts, which is why their resistance to corrosion is significantly lower. The low content of chromium is also what makes them magnetic, unlike austenitic grades which are nonmagnetic due to higher levels of chromium.

Always ask for EN 10204 3.1B test certificate from austenitic and martensitic stainless steel manufacturers in India.

Welding austenitic and martensitic stainless steel

Although stainless steels have good weldability, this property can be achieved by modifying the content of carbon in their alloy. A lowered carbon content with inclusions of nitrogen improves the weldability of the 300 series stainless steel. Having a higher content of carbon in its alloy makes it difficult to weld martensitic grades. Therefore, during the welding of these alloy grades, it is necessary to conduct both a preheat as well as post-weld heat treatment.

Austenitic and martensitic stainless steel grades

Martensitic stainless steels are available on the basis of their chemistry and are further classified into four categories. Grades with Fe-Cr-C Chemistry tend to be wear-resistant and are useful for engineering. Similar to the former are grades with Fe-Cr-Ni-C chemistry. These grades have some carbon content replaced with nickel and exhibit properties such as good casting properties, weldability, and resistance to cavitation erosion. Precipitation hardening grades exhibit properties like high strength and good toughness, whereas Creep-resisting Martensitic stainless steel grades are produced with trace quantities of elements like niobium, vanadium, boron, and cobalt. By adding these elements, there is an increase in the mechanical strength, with creep resistance up to a temperature of 650 °C. The austenitic class can further be segregated into two more categories i.e. 200 series and 300 series. While the 300 series are popular, the inclusion of nitrogen in the chemistry of the 200 series gives them an increase of approximately 50% yield strength in comparison to the 300 series.

Martensitic stainless steel grades

  • 410
  • 420
  • 430F
  • 440C
  • 431
  • 630 (17/4PH)

300 series austenitic stainless steel

Series Grade
300 Series 301 - 302 - 303 - 304/L - 304H - 316/L - 317L - 317LMN - 321 - 321H - 347 - 347H -309 - 309S - 310 - 310S - 310H - 330

Martensitic stainless steel Chemical composition

EN Steel designation European EN AISI C Cr Mo Others
X12Cr13 1.4006 410 0.12 12.5 - -
X20Cr13 1.4021 420 0.20 13.0 - -
X50CrMoV15 1.4116 - 0.50 14.5 0.65 V: 0.15
X14CrMoS17 1.4104 430F 0.14 16.5 0.40 S: 0.25
X39CrMo17-1 1.4122 - 0.40 16.5 1.10 -
X105CrMo17 1.4125 440C 1.10 17.0 0.60 -
X17CrNi16-2 1.4057 431 0.17 16.0 - Ni: 2.00
X4CrNiMo16-5-1 1.4418 - ≤ 0.06 16.0 1.10 Ni: 2.00
X5CrNiCuNb16-4 1.4542 630 (17/4PH) ≤ 0.07 16.0 - Ni: 4.00

Cu: 4.00

Nb: 5xC to 0.45

Martensitic stainless steel mechanical properties

EN Mininmum Yield stress, MPa Tensile strength, MPa Minimum Elongation, % Heat treatment
1.4006 450 650 - 850 15 QT650
1.4021 600 650 - 850 12 QT800
1.4122 550 750 - 950 12 QT750
1.4057 700 900 - 1050 12 QT900
1.4418 700 840 - 1100 16 QT900
1.4542 790 960 - 1160 12 P960

Austenitic stainless steel chemical composition

Euronorm (EN) Standard EN designation AISI grade C Cr Mo Ni Others
1.4310 X10CrNi18-8 301 0.10 17.5 NS 8 NS
1.4301 X5CrNi18-10 304 < 0.07 18.5 NS 9 NS
1.4307 X2CrNi18-9 304L < 0.030 18.5 NS 9 NS
1.4305 X8CrNiS18-9 e 303 < 0.10 18 NS 9 0.3
1.4541 X6CrNiTi18-10 321 < 0.08 18 NS 10.5 Ti: 5×C ≤ 0.70
1.4401 X5CrNiMo17-12-2 316 < 0.07 17.5 2.2 11.5 NS
1.4404 X2CrNiMo17-12-2 316L < 0.030 17.5 2.25 11.5 NS
1.4571 X6CrNiMoTi17-12-2 316Ti < 0.08 17.5 2.25 12 Ti: 5×C ≤ 0.70

Austenitic stainless steel grades list

  • 301
  • 304
  • 304L
  • 303
  • 321
  • 316
  • 316L
  • 316Ti

Different Austenitic stainless steel standard

  • SAE (also AISI, USA)
  • UNS (USA)
  • British Standards/ UK (BS)
  • International Standards Organisation (ISO)
  • European Standards (EN)
  • Japan Industrial Standards (JIS)
  • Germany Standard (DIN)
  • GB (China)

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