stainless steels

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What are stainless steels


Alloys of iron, chromium and other elements that resist corrosion in many environments
A minimum of ~12% Cr is required for it to be a stainless steel

Ferritic stainless steels

Have a BCC ferrite microstructure
Low carbon contents (<0.2%)
Cr in the range 12-20%
They remain ferritic all the way up to melting point
Poor weldability
Extra low interstitial grades developed with improved weldability


Martensitic stainless steels

Contain 12-18%Cr and 0.15-1.2%C
Amenable to strengthening by heat treatment, unlike the ferritic SSs.
The heat treatment comprises of quenching from austenitic phase field to produce martensite and tempering the martensite.

Super 12%Cr Martensitic Stainless Steels

In additions to the standard grades, a large number of alloyed martensitic stainless steels have been developed for moderately high temperature applications.
Most common additions include Mo, V and Nb.
These lead to a complex precipitation sequence.
The 12Cr-Mo-V-Nb steels are used in the power generation industry, for steam turbine blades operating at temperatures around 600 C.