{"id":1030,"date":"2025-02-21T11:27:40","date_gmt":"2025-02-21T11:27:40","guid":{"rendered":"https:\/\/expanite.com?page_id=1030"},"modified":"2026-08-17T08:11:26","modified_gmt":"2026-08-17T08:11:26","slug":"duplex","status":"publish","type":"page","link":"https:\/\/expanite.com\/it\/indurimento-superficiale\/leghe\/duplex\/","title":{"rendered":"Acciaio inossidabile duplex"},"content":{"rendered":"

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Duplex<\/span> Stainless Steel hardening<\/span><\/h1>\n

Expanite Surface Hardening For a Variety of Stainless Steel Alloys Including Duplex<\/h2>\n
These grades are referred to as duplex (or austenitic-ferritic) alloys due to their unique metallurgical structure, which comprises two phases:<\/div>\n
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Duplex stainless steels<\/a> are a family of stainless steels. These are called duplex (or austenitic-ferritic) grades because their metallurgical structure consists of two phases, austenite (face-centered cubic lattice) and ferrite (body centered cubic lattice) in roughly equal proportions.<\/p>\n

They provide better corrosion resistance, particularly chloride stress corrosion and chloride pitting corrosion, and higher strength than standard austenitic stainless steels such as A2\/304 or A4\/316. The main differences in composition, when compared with austenitic stainless steel is that duplex steels have a higher chromium content, 20\u201328%; higher molybdenum, up to 5%; lower nickel, up to 9% and 0.05\u20130.50% nitrogen. Both the low nickel content and the high strength (enabling thinner sections to be used) give significant cost benefits. Duplex steels also have higher strength. For example, a Type 304 stainless steel has a 0.2% proof strength in the region of 280 MPa (41 ksi), a 22%Cr duplex stainless steel a minimum 0.2% proof strength of some 450 MPa (65 ksi) and a superduplex grade a minimum of 550 MPa (80 ksi).[6]<\/p>\n

Duplex steels are used extensively in the offshore oil and gas industry for pipework systems, manifolds, risers, etc. and in the petrochemical industry for pipelines and pressure vessels.<\/p>\n

Learn More on Wikipedia<\/a><\/strong><\/p>\n<\/div>\n

UNS S31803 \/ S32205 \/ AISI 318LN \/ 1.4462 \/ Alloy 2205<\/h2>\n
Alloy 2205 offers an excellent combination of strength and corrosion resistance due to its chemical composition and duplex microstructure consisting of austenite and ferrite phases. Duplex stainless steel has twice the annealed yield strength of typical austenitic stainless steels. In the hot rolled unannealed condition, a yield strength of 75 ksi (518 MPa) or higher can be achieved for bar diameters up to 1.375 in. (34.925mm). Duplex possesses good resistance to general corrosion in many acid environments and, has excellent resistance to chloride stress corrosion cracking, pitting and crevice corrosion.<\/div>\n

UNS S32750 \/ AISI F53 \/ 1.4410 \/ Alloy 2507<\/h2>\n
Alloy 2507 is a super-duplex stainless steel with a microstructure consisting of austenite and ferrite phases in approximately equal amounts. The chemical composition and microstructure impart a good combination of strength, corrosion resistance and toughness with an annealed yield strength twice that of typical austenitic stainless steels possessing comparable impact strength. AISI F53 exhibits good resistance to general corrosion in many acid environments with exceptional resistance to chloride stress corrosion cracking, pitting and crevice corrosion.<\/p>\n<\/div>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
EN designation<\/th>\nEuronorm (EN) number<\/th>\nAISI grade<\/th>\n<\/th>\n<\/tr>\n<\/thead>\n
X2CrNiN22-2 <\/td>\n1.4062 <\/td>\nS32202 <\/td>\nn\/a<\/td>\n<\/tr>\n
X2CrCuNiN23-2-2<\/td>\n1.4669<\/td>\n<\/td>\n\n

None<\/p>\n<\/td>\n<\/tr>\n

X2CrNiMoSi18-5-3<\/td>\n1.4424<\/td>\nS31500<\/td>\n\n

None<\/p>\n<\/td>\n<\/tr>\n

X2CrNiN23-4<\/td>\n1.4362<\/td>\nS32304<\/td>\n\n

None<\/p>\n<\/td>\n<\/tr>\n

X2CrMnNiN21-5-1<\/td>\n1.4162<\/td>\nS32101<\/td>\n\n

None<\/p>\n<\/td>\n<\/tr>\n

X2CrMnNiMoN21-5-3<\/td>\n1.4482<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMoN22-5-3<\/td>\n1.4462<\/td>\nS31803<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMnMoCuN24-4-3-2<\/td>\n1.4662<\/td>\nS32205<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMoCuN25-6-3<\/td>\n1.4507<\/td>\nS32520<\/td>\n<\/td>\n<\/tr>\n
X3CrNiMoN27-5-2<\/td>\n1.4460<\/td>\nS31200<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMoN25-7-4<\/td>\n1.4410<\/td>\nS32750<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMoCuWN25-7-4<\/td>\n1.4501<\/td>\nS32760<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMoN29-7-2<\/td>\n1.4477<\/td>\nS32906<\/td>\n<\/td>\n<\/tr>\n
X2CrNiMoCoN28-8-5-1<\/td>\n1.4658<\/td>\nS32707<\/td>\n<\/td>\n<\/tr>\n
X2CrNiCuN23-4<\/td>\n1.4655<\/td>\nS32304<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The Purpose of the Process<\/h2>\n

ExpaniteHigh-T<\/h2>\n
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The purpose of this process is to dissolve nitrogen in the surface of stainless steel to a depth of 1mm. Peak hardness ranges from 280HV on austenitic grades to 950HV on martensitic\/ferritic grades.<\/p>\n<\/div>\n

ExpaniteLow-T<\/h2>\n
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The purpose of this process is to dissolve nitrogen and carbon in the surface of stainless steel to a depth in the range of 5-30\u00b5m. Peak hardness ranges from 1100-1300HV on all grades.<\/p>\n<\/div>\n

SuperExpanite\u00ae<\/h2>\n
The purpose of this process is to combine ExpaniteHigh-T and ExpaniteLow-T processes to achieve higher load bearing and corrosion properties. Firstly, the ExpaniteHigh-T process is applied to create a deep case depth with moderate nitrogen content. Secondly, the ExpaniteLow-T process is applied to create a high-hardness surface on top of the ExpaniteHigh-T zone. The Expanite process does not result in a coating, but a diffusion zone with an increased carbon and nitrogen content. We call this zone expanded austenite, expanded martensite or simply: Expanite.<\/div>\n

Discover More Stainless Steel Solutions with Expanite<\/h2>\n
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Expanite\u00ae surface hardening and heat treatment solutions unlock the full potential of duplex stainless steels by improving wear resistance, eliminating galling, and extending component lifetime without compromising corrosion resistance. With our proven expertise, we help customers in demanding industries achieve superior performance and reliability.<\/p>\n

To gain a complete overview of how Expanite can support your material choices, we also invite you to explore our dedicated pages on Austenitic<\/a>, Ferritic<\/a>, and Martensitic<\/a> stainless steels \u2013 and discover how our technology adds value across the full range of stainless steel alloys.<\/p>\n<\/div>\n

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