# US 9,039,960 B2 · Methods for processing nanostructured ferritic alloys, and articles produced thereby

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- Number: US 9,039,960 B2
- Document ID: US9039960B2
- Status: Granted
- Kind: B2
- Application number: 13/745,506
- Filed: 2013-01-18
- Published: 2013-05-23
- Granted: 2015-05-26
- Earliest claimed: 2009-12-14
- Assignees: General Electric Company
- Applicants: General Electric Company
- Inventors: Richard Didomizio; Matthew Joseph Alinger; Raymond Joseph Stonitsch; Samuel Vinod Thamboo
- Web page: https://patentgrep.com/patent/US9039960B2

## CPC

- B22F 5/00: Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F 3/15: Hot isostatic pressing
- B22F 3/24: After-treatment of workpieces or articles {(B22F3/1146 takes precedence)}
- C22C 33/0285: {with Cr, Co, or Ni having a minimum content higher than 5%}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/22: with molybdenum or tungsten
- C22C 38/28: with titanium or zirconium
- F01D 5/286: {Particular treatment of blades, e.g. to increase durability or resistance against corrosion or erosion (F01D5/288 takes precedence)}
- B22F 2003/247: {Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface}
- B22F 2998/10: Processes characterised by the sequence of their steps
- F05D 2230/00: Manufacture
- F05D 2230/90: Coating; Surface treatment
- F05D 2300/502: Thermal properties
- Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D)
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A formed article comprising a nanostructured ferritic alloy is provided. Advantageously, the article is not formed via extrusion, and thus, cost savings are provided. Methods are also provided for forming the article, and the articles so produced, exhibit sufficient continuous cycle fatigue crack growth resistance and hold time fatigue crack growth resistance to be utilized as turbomachinery components, and in particular, large, hot section components of a gas or steam turbine engines. In other embodiments, a turbomachinery component comprising an NFA is provided, and in some such embodiments, the turbomachinery component may be extruded.

## Claims

### Claim 1

A method of forming a turbomachinery component comprising a nanostructured ferritic alloy, the method comprising the steps:
forming a melt of an Fe—Ti—Cr alloy, processing the melt to form a powder of the alloy, milling the powder in the presence of an oxide to dissolve the oxide into the alloy to form a milled powder, wherein the oxide is yttrium oxide or yttrium oxide in combination with aluminum oxide and/or hafnium oxide;
hot isostatic pressing the milled powder under an inert environment to form a hot isostatic pressed nanostructured ferritic alloy preform, and
forging the nanostructured ferritic alloy preform into a turbomachinery component wherein the steps are performed in the absence of extrusion,
wherein the hot isostatic pressing is performed in a temperature range of about 900° C. to about 1200° C. for at least about one hour under a pressure of at least about 20 ksi and the inert environment is vacuum to achieve a hot isostatic pressed preform having a thickness and
wherein the forging is performed at a temperature of about 1000° C. to about 1200° C. to reduce the thickness by at least about 30%.

### Claim 2 (depends on 1)

The method of claim 1, wherein the powder of the alloy is formed by atomizing wherein the atomizing is performed by at least one of gas atomization, water atomization, rotating electrode atomization, or combinations thereof.

### Claim 3 (depends on 1)

The method of claim 1, wherein the Fe—Ti—Cr alloy is martensitic, austenitic, duplex, or ferritic steel.

### Claim 4 (depends on 1)

The method of claim 1, wherein the hot isostatic pressing is continued to produce a nanostructured ferritic alloy preform having a density greater than 95% of theoretical density.

### Claim 5 (depends on 1)

The method of claim 1, wherein forging of the preform is performed to produce a forged turbomachinery component having a density greater than 98% of theoretical density.

### Claim 6 (depends on 5)

The method of claim 5, further comprising machining the forged turbomachinery component.

### Claim 7 (depends on 1)

The method of claim 1, wherein the forged turbomachinery component exhibits a continuous cycle fatigue crack growth rate at 1000° F. at a stress intensity factor k of 45 ksi*in0.5 of less than about 1.20E−4 in/cycle.

### Claim 8 (depends on 7)

The method of claim 7, wherein the forged turbomachinery component exhibits a continuous cycle fatigue crack growth rate at 1000° F. at a k of 45 ksi*in0.5 of less than about 9.03−5 in/cycle.

### Claim 9 (depends on 1)

The method of claim 1, wherein the forged turbomachinery component exhibits a hold time fatigue crack growth rate at 1000° F. at a k of 45 ksi*in0.5 of less than about 1.80E−3 in/hr.

### Claim 10 (depends on 9)

The method of claim 9, wherein the forged turbomachinery component exhibits a hold time fatigue crack growth rate at 1000° F. at a k of 45 ksi*in0.5 of less than about 1.35E−3 in/hr.

### Claim 11 (depends on 1)

The method of claim 1, wherein yttrium oxide is added to the powder of the alloy and the nanostructured ferritic alloy comprises Fe, Ti, Cr and nanofeatures comprising Ti—O and Y produced by the combination of Ti in the Fe—Ti—Cr alloy with the yttrium oxide added to the powder of the Fe—Ti—Cr alloy.

### Claim 12 (depends on 11)

The method of claim 11, wherein yttrium oxide and aluminum oxide are added to the powder of the Fe—Ti—Cr alloy.

### Claim 13 (depends on 1)

The method of claim 1 wherein the nanostructured ferritic alloy comprises Fe, Ti, Cr, and incidental impurities and nanofeatures comprising oxides comprised of Ti, O, Y and further comprises at least one of Hf, Fe, Cr, Mo, W, Mn, Si, Nb, Ni or Ta.

### Claim 14 (depends on 1)

The method of claim 1 wherein the nanostructured ferritic alloy is dispersion strengthened by nanofeatures comprising Ti—O and Y.

### Claim 15 (depends on 1)

The method of claim 1 wherein the nanostructured ferritic alloy is dispersion strengthened by nanofeatures comprising Ti—O and Y and at least one of Hf, Fe, Cr, Mo, W, Mn, Si, Nb, Ni or Ta.

### Claim 16 (depends on 1)

The method of claim 1 wherein the forging is performed to reduce the thickness by at least about 40%.

### Claim 17 (depends on 1)

The method of claim 1 wherein the forging is performed to reduce the thickness by at least about 50%.

### Claim 18 (depends on 1)

The method of claim 1 wherein the nanostructured ferritic alloy comprises Fe, Ti, Cr, and incidental impurities, and nanofeatures comprising Ti—O and Y.

### Claim 19 (depends on 18)

The method of claim 18 wherein the nanostructured ferritic alloy comprises about 5 wt % to about 30 wt % chromium, 0.1 wt % to about 2 wt % titanium, about 0 wt % to about 5 wt % molybdenum, about 0 wt % to about 5 wt % tungsten, about 0 wt % to about 5 wt % manganese, about 0 wt % to about 5 wt % silicon, about 0 wt % to about 2 wt % niobium, about 0 wt % to about 2 wt % aluminum, about 0 wt % to about 8 wt % nickel, about 0 wt % to about 2 wt % tantalum, about 0 wt % to about 0.5 wt % carbon, about 0 wt % to about 0.5 wt % nitrogen, and yttrium oxide, with the balance being iron and incidental impurities.

### Claim 20

A method of forming a turbomachinery component comprising a nanostructured ferritic alloy, wherein the method comprises vacuum induction melting a ferritic alloy matrix comprising Fe-14Cr-0.4Ti-3W-0.5Mn-0.5Si (wt %) to form a melt of the alloy matrix, atomizing the melt with argon gas to form atomized powder of the ferritic alloy matrix, mixing the atomized powder with yttrium oxide to form a mixed powder, milling the mixed powder until the yttrium oxide is dissolved into the ferritic alloy matrix to form a doped powder, and hot isostatic pressing the doped powder in a vacuum at 30 ksi for 4 hours at 1150° C. to form a hot isostatic pressed nanostructured ferritic alloy turbomachinery component.

### Claim 21 (depends on 20)

The method of claim 20 further comprising forging the hot isostatic pressed turbomachinery component.