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Corrosion resistant article and methods of making

a technology of corrosion resistance and articles, applied in the field of nanostructured ferritic alloys, can solve the problems of low strength, low to intermediate strength, and poor corrosion resistance of duplex steels

Inactive Publication Date: 2016-07-21
GENERAL ELECTRIC CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes an article that has a surface with a special alloy made up of nanofeatures. This alloy has been made by a process involving milling, consolidation, annealing, and cooling. The article also has a small amount of another phase called chi or sigma. The technical effect of this invention is an improved material with better properties, such as enhanced hardness and strength.

Problems solved by technology

In general, ferritic steels have improved stress corrosion cracking resistance in chloride-containing environments, but the strength is relatively low.
Austenitic and duplex steels have good corrosion resistance, low to intermediate strength, but inferior stress corrosion cracking resistance.

Method used

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  • Corrosion resistant article and methods of making
  • Corrosion resistant article and methods of making
  • Corrosion resistant article and methods of making

Examples

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example

[0044]The following example illustrates the method, materials and results, in accordance with specific embodiments, and as such should not be construed as imposing limitations upon the claims. All components are commercially available from common chemical suppliers.

[0045]In one example method of preparation, pre-alloyed steel (Fe—Cr) powders doped with elemental metal powders (Cr, Mo, Ni, W, Ti) and iron nitride powder as necessary to match the nominal composition of the desired duplex NFA were taken as starting materials and mixed with Y2O3 powder. Nominal composition of the desired duplex NFA in this example was Fe-25Cr-3.5Mo-7Ni-0.25N-0.75W-0.4Ti-0.25Y2O3. Alternatively, pre-alloyed powders containing a mixture of 3 or more elements selected from Fe, Cr, Mo, Ni, W, and Ti may also be used as starting powders. Powders were mixed with 420 stainless steel balls (˜4.5 mm in diameter) with a 10:1 ratio and milled in a high energy attrition mill for about 20 hours in an argon environme...

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Abstract

An article and method of forming the article are disclosed. The article has a surface comprising a duplex nanostructured ferritic alloy. The surface includes a plurality of nanofeatures that include complex oxides of yttrium and titanium disposed in an iron-bearing alloy matrix. The iron-bearing alloy matrix includes both a ferrite phase and an austenite phase. Further, a concentration of a chi phase or a sigma phase in the duplex nanostructured ferritic alloy at the surface is less than about 5 volume percent. The method generally includes the steps of milling, thermo-mechanically consolidating, annealing, and then cooling at a rate that hinders the formation of chi and sigma phases in the duplex nanostructured ferritic alloy at the surface.

Description

BACKGROUND[0001]The invention relates generally to a nanostructured ferritic alloy comprising a duplex microstructure (referred to as the duplex NFA) and articles made of such alloys. More particularly, the invention relates to an article having a duplex nanostructured ferritic alloy surface with good corrosion resistance, and methods of forming the article.[0002]Material selection is especially important in equipment components used in sour and acid environments commonly associated with oil and gas extraction installations. Sour gas wells may contain carbon dioxide, chlorides, hydrogen sulfides, and free sulfur, and may operate at temperatures up to 400° C. This type of corrosive environment requires carefully designed alloys to enable components to maintain their structural integrity over their service life.[0003]Conventional corrosion resistant steels include ferritic, austenitic, and ferritic / austenitic duplex steels. In general, ferritic steels have improved stress corrosion cr...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B22F5/00B22F3/20B22F3/17B22F3/15B22F3/14
CPCB22F5/00B22F3/15B22F2003/175B22F3/17B22F3/20B22F3/14C21D1/26C22C32/0026C22C33/0285C22C38/001C22C38/44C21D2211/005C21D2211/004C21D2211/001C21D6/004C21D2241/02B22F2998/10B22F9/04C22C1/1084B22F3/02B22F2003/248B22F3/16C22C33/02
Inventor HUANG, SHENYANREBAK, RAUL BASILIODIDOMIZIO, RICHARDPIETRANGELI, EMANUELE
Owner GENERAL ELECTRIC CO
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