Transformation enabled nitride magnets absent rare earths and a process of making the same

Patent metadata

Field	Value
Publication number	US-9997285-B2
Application number	US-201414304102-A
Country	US
Kind code	B2
Filing date	Jun 13, 2014
Priority date	Dec 15, 2011
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A process for producing an ordered martensitic iron nitride powder that is suitable for use as a permanent magnetic material is provided. The process includes fabricating an iron alloy powder having a desired composition and uniformity; nitriding the iron alloy powder by contacting the material with a nitrogen source in a fluidized bed reactor to produce a nitride iron powder; transforming the nitride iron powder to a disordered martensitic phase; annealing the disordered martensitic phase to an ordered martensitic phase; and separating the ordered martensitic phase from the iron nitride powder to yield an ordered martensitic iron nitride powder.

First claim

What is claimed is:

1. A process for producing a single-phase γ-austenite iron-based alloy nitride powder that is suitable for producing a martensitic iron-based alloy nitride powder, comprising the steps of:
a) providing an iron-based alloy powder; and
b) nitriding the iron-based alloy powder by contacting the material with a nitrogen source, thereby producing the single-phase γ-austenite iron-based alloy nitride powder;
wherein the iron-based alloy powder has an alloy composition that enables a greater amount of nitrogen to be soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding as compared to a maximum solubility of nitrogen in elemental iron that is nitrided under the same conditions,
wherein the nitrogen content soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding is in the range from greater than 10.3 at. % to 11.1 at. %.

2. The process according to claim 1 , wherein the nitrogen content soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding is 11.1 at. %.

3. The process according to claim 1 , wherein the single-phase γ-austenite iron-based alloy nitride powder produced during the nitriding consists of the austenitic γ-phase iron-based alloy as a single-phase solid solution having the nitrogen diffused interstitially into the iron-based alloy lattice structure.

4. The process according to claim 1 , wherein the single-phase γ-austenite iron-based alloy nitride powder includes chromium as an alloying element that enables the greater solubility of nitrogen during the nitriding.

5. The process according to claim 4 , wherein the single-phase γ-austenite iron-based alloy nitride powder includes 11.1 at. % nitrogen and chromium in a range from 0.9 at. % to 2.7 at. %.

6. The process according to claim 4 , wherein a compositional uniformity of the chromium in the single-phase γ-austenite iron-based alloy nitride powder is 1.0±0.1 at. %.

7. The process according to claim 1 , wherein the single-phase γ-austenite iron-based alloy nitride powder includes manganese as an alloying element that enables the greater solubility of nitrogen during the nitriding.

8. The process according to claim 7 , wherein the single-phase γ-austenite iron-based alloy nitride powder includes 11.1 at. % nitrogen and manganese in a range from 3.1 at. % to 8.7 at. %.

9. A process for producing a single-phase γ-austenite iron-based alloy nitride powder that is suitable for producing a martensitic iron-based alloy nitride powder, comprising the steps of:
a) providing an iron-based alloy powder; and
b) nitriding the iron-based alloy powder by contacting the material with a nitrogen source, thereby producing the single-phase γ-austenite iron-based alloy nitride powder;
wherein the iron-based alloy powder has an alloy composition that enables a greater amount of nitrogen to be soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding as compared to a maximum solubility of nitrogen in elemental iron that is nitrided under the same conditions,
wherein the nitriding includes diffusing nitrogen interstitially into the iron-based alloy lattice structure at a ratio of 16:2 metal:nitrogen.

10. A process for producing a single-phase γ-austenite iron-based alloy nitride powder that is suitable for producing a martensitic iron-based alloy nitride powder, comprising the steps of:
a) providing an iron-based alloy powder; and
b) nitriding the iron-based alloy powder by contacting the material with a nitrogen source, thereby producing the single-phase γ-austenite iron-based alloy nitride powder;
wherein the iron-based alloy powder has an alloy composition that enables a greater amount of nitrogen to be soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding as compared to a maximum solubility of nitrogen in elemental iron that is nitrided under the same conditions,
wherein the single-phase γ-austenite iron-based alloy nitride powder includes aluminum as an alloying element that enables the greater solubility of nitrogen during the nitriding.

11. The process according to claim 10 , wherein the single-phase γ-austenite iron-based alloy nitride powder includes aluminum in a range from 1.7 at. % to 5.2 at. %.

12. The process according to claim 11 , wherein the nitrogen content soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding is in the range from greater than 10.3 at. % to 11.1 at. %.

13. A process for producing a single-phase γ-austenite iron-based alloy nitride powder that is suitable for producing a martensitic iron-based alloy nitride powder, comprising the steps of:
a) providing an iron-based alloy powder; and
b) nitriding the iron-based alloy powder by contacting the material with a nitrogen source, thereby producing the single-phase γ-austenite iron-based alloy nitride powder; wherein the iron-based alloy powder has an alloy composition that enables a greater amount of nitrogen to be soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitridinq as compared to a maximum solubility of nitrogen in elemental iron that is nitrided under the same conditions,
wherein the single-phase γ-austenite iron-based alloy nitride powder includes chromium as an alloying element that enables the greater solubility of nitrogen during the nitriding, the chromium being in a range from 0.9 at. % to 2.7 at. %.

14. The process according to claim 13 , wherein the nitrogen content soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding is in the range from greater than 10.3 at. % to 11.1 at. %.

15. A process for producing a single-phase γ-austenite iron-based alloy nitride powder that is suitable for producing a martensitic iron-based alloy nitride powder, comprising the steps of:
a) providing an iron-based alloy powder; and
b) nitriding the iron-based alloy powder by contacting the material with a nitrogen source, thereby producing the single-phase γ-austenite iron-based alloy nitride powder;
wherein the iron-based alloy powder has an alloy composition that enables a greater amount of nitrogen to be soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitriding as compared to a maximum solubility of nitroqen in elemental iron that is nitrided under the same conditions,
wherein the nitriding includes diffusing nitrogen interstitially into the iron-based alloy lattice structure via exposure to the nitrogen source in a fluidized bed reactor.

16. A process for producing a single-phase γ-austenite iron-based alloy nitride powder that is suitable for producing a martensitic iron-based alloy nitride powder, comprising the steps of:
a) providing an iron-based alloy powder; and
b) nitriding the iron-based alloy powder by contacting the material with a nitrogen source, thereby producing the single-phase γ-austenite iron-based alloy nitride powder;
wherein the iron-based alloy powder has an alloy composition that enables a greater amount of nitrogen to be soluble in the single-phase γ-austenite iron-based alloy nitride powder during the nitridinq as compared to a maximum solubility of nitroqen in elemental iron that is nitrided under the same conditions,
further comprising the step:
transforming the single-phase γ-austenite iron-based alloy nitride powder to a disordered α′-martensitic phase iron-based alloy nitride powder.

17. The process according to claim 16 , wherein the step of transforming includes subjecting th

Assignees

• Univ Case Western Reserve

Inventors

• Matthiesen David

Classifications

• C04B35/6268

  characterised by the applied pressure or type of atmosphere, e.g. in vacuum, hydrogen or a specific oxygen pressure · CPC title

• H01F1/083

  in a bonding agent · CPC title

• C01P2002/54

  one element only · CPC title

• H01F1/065

  obtained by a reduction · CPC title

• C04B2235/465

  Ammonia · CPC title