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The Basics of Ferrous Metallurgy

102 Articles

Martensitic High Nitrogen (Stainless) Steels

Martensitic high nitrogen stainless steels are particularly interesting because they typically exhibit high strength and ductility, good corrosion resistance and reduced grain boundary sensitization.
This articles explores the possibility of the use of martensitic high nitrogen stainless steels for cryotechnic bearings for aerospace applications where requirements stipulate that no crack initiation can be tolerated.

Medium Manganese Steels: Part One

Medium manganese steels should be considered in the same circles of many of the technologically focused and well known materials in the automotive industry such as AHSS, DP, CP as well as second generation steels.
Medium-Mn steels show a strong tendency for transformation-induced plasticity (TRIP) or twinning induced plasticity (TWIP) depending on the stability of the retained austenite.

Metallography: Part One

Microstructural examinations and visual evaluations of fracture surfaces provide an invaluable insight into the mechanism of component and assembly failures.
Typically, the metallography process uses sample specimens removed and mounted in bakelite plastic. The specimens are then ground to a fine finish with sandpaper and then polished to a mirror finish with diamond or alumina polishing materials.

Metallography: Part Three

The purpose of the coarse grinding stage is to generate the initial flat surface necessary for the subsequent grinding and polishing steps. As a result of sectioning and grinding, the material may get cold worked to a considerable depth with a resultant transition zone of deformed material between the surface and the undistorted metal.
Each stage of metallographic sample preparation must be carefully performed; the entire process is designed to produce a scratch free surface by employing a series of successively finer abrasives.

Metallography: Part Two

The technique for preparing metal sections can be divided into two groups, those processes involving the use of emery papers and coarse abrasives (grinding) and the subsequent operations using fine abrasives (polishing treatments).
Compression-type molding is commonly applied to encase specimens in 1 to 1.5 inch diameter plugs of a hardened polymer.

Microstructures in Austenitic Stainless Steels

Austenitic stainless steels undergo significant microstructural changes during exposure to elevated temperatures, with both short-term and long-term transformations affecting their properties. Initially, M23C6 carbides form during brief heat exposure, while extended aging leads to intermetallic phase precipitation and carbide dissolution. These transformations substantially influence both mechanical performance and corrosion resistance.