Materials / Duplex & Super-Duplex Stainless

Duplex & Super-Duplex Stainless Steel

Duplex grades combine ferritic and austenitic phases for higher yield strength than standard austenitic stainless plus superior pitting and stress-corrosion resistance. Monmet supplies duplex and super-duplex castings and forgings for offshore and chloride service.

Quick answer

Duplex and super-duplex stainless combine ferritic and austenitic phases for higher yield strength than standard austenitic stainless, plus superior resistance to pitting and stress-corrosion cracking in chloride service. Used across oil & gas, desalination and chemical processing. Monmet supplies duplex castings and forgings, solution-annealed and water-quenched to control microstructure.

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Grades

Lean duplex, standard duplex, super-duplex and hyper-duplex grades are available as castings and forgings.

Critical Properties

Higher yield strength than standard austenitic stainless, a balanced ferrite-austenite microstructure, and freedom from harmful sigma phase.

Quality Control

Ferrite measurement, intergranular and pitting corrosion tests, micrograph review for harmful intermetallics, solution-annealing followed by water quench.

Frequently Asked Questions

Sigma phase (Cr-rich intermetallic) forms between 650–950 °C, embrittling duplex and depleting Cr from the matrix. Rapid cooling from solution-anneal is mandatory.

Use matching or over-alloyed filler, control heat input, and verify ferrite balance on welds.

Duplex use is limited to a moderate temperature range to avoid embrittlement and low-temperature ferrite cleavage; tell us your service conditions and we confirm suitability at quotation.

Related Materials

Stainless Steel

Stainless steel castings and forgings in austenitic, martensitic, ferritic and duplex families. Corrosion-resistant components from small precision parts to very large single-piece castings.

Nickel Alloys (Inconel, Monel, Incoloy)

Nickel-based alloy castings and forgings, including Inconel, Monel and Incoloy grades, for high-temperature, corrosive and marine service.

Hastelloy Alloys

Hastelloy castings and forgings for chemical processing, FGD scrubbers and reducing-acid environments.

Material Selection Guide

How to choose the right cast or forged alloy: strength, corrosion, temperature, cost and processability — Monmet's engineering selection guide.

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