The key difference between austenitic and martensitic stainless steel is that the crystal structure of austenitic stainless steel is a face-centred cubic structure, whereas the crystal structure of martensitic stainless steel is a body-centred cubic structure.
There are four major groups of stainless steel according to the crystal structure of the steel: austenitic, ferritic, martensitic and duplex. This microstructure of these alloys depends on the alloying elements present in them; thus, these alloys have different alloying elements as well.
CONTENTS
1. Overview and Key Difference
2. What is Austenitic Stainless Steel
3. What is Martensitic Stainless Steel
4. Side by Side Comparison – Austenitic vs Martensitic Stainless Steel in Tabular Form
5. Summary
What is Austenitic Stainless Steel?
Austenitic stainless steel is a form of stainless steel alloy which has exceptional corrosion resistance and impressive mechanical properties. The primary crystal structure of this alloy is a face-centred cubic structure, and it possesses “austenite” (a metallic and non-magnetic allotrope of iron or a solid solution of iron with an alloying element).
Figure 01: Austenitic Stainless Steel
Furthermore, this material has better strength, toughness, formability, and ductility. These materials are useful in cryogenic (low) and high-temperature applications as well. Moreover, they are aesthetically valuable. When considering the structure, it has a face-centred cubic structure in which there is one atom at each corner of the cube, and there is one atom in each face (at the centre of the face). The structure is formed when a sufficient amount of nickel is mixed with iron and chromium. Usually, this material contains about 15% chromium and 8 to 10% nickel.
What is Martensitic Stainless Steel?
Martensitic stainless steel is an alloy which has more chromium and ordinarily no nickel in it. And, this material can be either high carbon or low carbon steel. Apart from that, it contains 12% iron, 17% chromium and 0.10% carbon. The notable properties of this material are mechanical properties and wear resistance.
Figure 02: Tweezers made from Martensitic Stainless Steel
Furthermore, the crystal structure of martensitic stainless steel is a body-centred cubic structure. Here, each corner of a cube contains atoms, and there is one atom in the centre of the cube. In the basic composition, there is no nickel in this material. In addition, this material is ferromagnetic, hardenable using heat treatments, less corrosion resistance, etc.
What is the Difference Between Austenitic and Martensitic Stainless Steel?
Austenitic stainless steel is a form of stainless steel alloy which has exceptional corrosion resistance and impressive mechanical properties, while martensitic stainless steels is an alloy which has more chromium and ordinarily no nickel in it. The key difference between austenitic and martensitic stainless steel is that the crystal structure of austenitic stainless steel is a face-centred cubic structure whereas for martensitic stainless steel it is a body-centred cubic structure.
Moreover, a further difference between austenitic and martensitic stainless steel is that the austenitic stainless steel contains nickel, but martensitic stainless steel does not. The nickel content in austenitic form is about 8 to 10 %. Apart from that, austenitic form is diamagnetic while martensitic form is ferromagnetic.
Summary – Austenitic vs Martensitic Stainless Steel
Austenitic stainless steel is a form of stainless steel alloy which has exceptional corrosion resistance and impressive mechanical properties, while martensitic stainless steels is an alloy which has more chromium and ordinarily no nickel in it. The key difference between austenitic and martensitic stainless steel is that the crystal structure of austenitic stainless steel is face-centred cubic structure whereas the crystal structure of martensitic stainless steel it is body-centred cubic structure.
Reference:
1. “Austenitic Stainless Steel.” Austenitic Stainless Steel – an Overview | ScienceDirect Topics, Available here.
Image Courtesy:
1. “Unsensitised structure of type 304 stainless steel” By Webcorr – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Tweezers made of martensitic stainless steel JIS SUS410” By Yapparina – Own work (CC0) via Commons Wikimedia