Method for forming a tubular medical device

• US 9,034,245 B2
• Filed: 02/25/2013
• Issued: 05/19/2015
• Est. Priority Date: 03/04/2010
• Status: Active Grant

• Current Assignee: Mirus LLC
• Original Assignee: Icon Medical Corp. (ICON Interventional Systems, Inc.)
• Inventors: Buckman, Raymond W. Jr., Patel, Udayan, Furst, Joseph
• Primary Examiner(s): Zhu, Weiping
• Application Number:
  US13/776,049
• Publication Number:
  US 20130216421A1
• Time in Patent Office: 813 Days
• Field of Search: 419/28, 148/237
• US Class Current: 419/5
• CPC Class Codes: A61F 2/91 made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
• CPC Class Codes: A61L 31/022 Metals or alloys
• CPC Class Codes: B21D 31/00 Other methods for working sheet metal, metal tubes, metal profiles deforming one surface of tubes helically by rolling B21H3/00; upsetting B21J5/08; working metal by removing material therefrom B23; embossing B44B
• CPC Class Codes: B22F 2003/247 Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
• CPC Class Codes: B22F 2003/248 Thermal after-treatment
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/20 by extruding
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: B22F 5/106 Tube or ring forms
• CPC Class Codes: C22C 27/04 Alloys based on tungsten or molybdenum
• CPC Class Codes: C22F 1/18 High-melting or refractory metals or alloys based thereon
• CPC Class Codes: C22F 1/183 of titanium or alloys based thereon
• CPC Class Codes: C23C 8/24 Nitriding

Abstract

A method and process for at least partially forming a medical device that is at least partially formed of a metal alloy which improves the physical properties of the medical device.

Claims

1. A method for forming a medical device comprising the steps of:

a) forming a rod or tube having a surface and an outer cross-sectional area, said rod or tube including a metal alloy that is formed of over 50 weight percent of a solid solution of molybdenum and rhenium or tungsten and tantalum;

b) drawing down said outer cross-sectional area of said rod or tube by a reducing mechanism;

c) annealing said rod or tube at an annealing temperature in an oxygen reducing environment or inert environment after said rod or tube has been drawn down;

d) drawing down said cross-sectional area of said rod or tube by the reducing mechanism after said rod or tube has been annealed; and

,

e) annealing said rod or tube at least one additional time at an annealing temperature that is a lower temperature than at least one annealing temperature of a previous annealing of said rod or tube.

2. The method as defined in claim 1, wherein said step of forming said rod or tube includes a process of isostatically pressing metal powder together and subsequently sintering said metal power to form said rod or tube in a controlled atmosphere, said rod or tube having an average density of about 0.7-0.95 a minimum theoretical density of said metal alloy, said rod or tube have an average density of about 12-14 gm/cc, said controlled atmosphere including an inert atmosphere, an oxygen reducing atmosphere, or a vacuum.

3. The method as defined in claim 2, wherein said tube is formed by gun drilling, EDM cutting, or combinations thereof a passageway at least partially through a longitudinal length of said rod.

4. The method as defined in claim 1, wherein said step of forming said rod or tube includes a) forming an ingot of metal, b) extruding said ingot through a die to form a rod, c) hollowing out said rod to form a passageway at least partially through a longitudinal length of said rod, and d) polishing a surface of said passageway.

5. The method as defined in claim 4, wherein said step of hollowing includes gun drilling, EDM cutting, or combinations thereof said rod to form said passageway.

6. The method as defined in claim 1, wherein said metal alloy includes over 50 weight percent rhenium plus molybdenum, and up to about 1 weight percent additional metal, said additional metal including a metal selected from the group consisting of titanium, yttrium, zirconium, or mixtures thereof.

7. The method as defined in claim 1, including the step of nitriding said rod or tube to form a nitride layer on said rod or tube prior to at least one drawing down step, said step of nitriding including a) exposing at least a portion of said rod or tube to a nitriding gas that includes nitrogen, nitrogen and hydrogen, or combinations thereof, and b) exposing at least a portion of said rod or tube to a nitriding gas at a temperature of less than about 400°

C. for at least about 1 minute.

8. The method as defined in claim 7, including the step of removing said nitride layer on said rod or tube prior to annealing said rod or tube.

9. The method as defined in claim 1, including the step of protecting said rod or tube from oxygen when said rod or tube is exposed to temperatures of greater than about 400°

C.

10. The method as defined in claim 1, wherein said step of drawing down said cross-sectional area of said rod or tube by a reducing mechanism that reduces said cross-sectional area by less than about 20% each time said rod or tube is processed by said reducing mechanism.

11. The method as defined in claim 10, wherein said step of drawing down includes the step of inserting a close-fitting rod in said passageway of said tube prior to using said reducing mechanism on said tube.

12. The method as defined in claim 1, wherein said step of annealing said rod or tube includes the steps of a) annealing the rod or tube at an annealing temperature of at least about 1480°

C. for a time period of at least about 5 minutes when said rod or tube has wall thickness of greater than about 0.015 inch, b) annealing the rod or tube at an annealing temperature of about 1450-1480°

C. for a time period of at least about 5 minutes when said rod or tube has wall thickness of about 0.008-0.015 inch, and c) annealing the rod or tube at an annealing temperature of less than about 1450°

C. for a time period of at least about 5 minutes when said rod or tube has wall thickness of less than about 0.008 inch.

13. The method as defined in claim 1, wherein said medical device is a stent.

14. The method as defined in claim 1, where said rod or tube after completion of all of the annealing steps has an average grain size of 4-14 ASTM.

15. The method as defined in claim 1, wherein said initial tube has a wall thickness of about 0.001-0.100 inch.