Methods for manufacturing radiopaque intraluminal stents comprising cobalt-based alloys with supersaturated tungsten content

1. A process for the production of a primarily single-phase FCC, cobalt-chromium alloy including tungsten, the process comprising:

forming an alloy melt including cobalt, chromium, nickel and tungsten, the tungsten being at least 20% to about 35% by weight of a solution, so that the tungsten content is above a solubility limit of tungsten in the cobalt-chromium alloy at ambient temperature and the chromium is 15% to 25% by weight of the solution;

heating the alloy melt to at least about 1500° C. for a time sufficient to form a single-phase solution;

cooling, without water quenching, the single-phase solution to 500K within a period of time of less than 10 minutes to preserve a primarily single-phase FCC solid solution structure, wherein no more than 10% volume fraction of a second phase is present, the second phase having an average particle size of less than 15 μm, even with the super-saturated tungsten content.

2. The process of claim 1 , wherein the solution comprises nickel in an amount from about 5% to about 15% by weight of the solution.

3. The process of claim 1 , wherein the cooling step is performed within a period of time of less than 1 minute.

4. The process of claim 1 , wherein the cooling step is performed by spraying the single-phase solution through a nozzle in order to form droplets of the single-phase solution.

5. The process of claim 4 , further comprising

cooling the droplets of the single phase solution into a powder,

compacting the powder, and

sintering the compacted powder into a billet.

6. The process of claim 1 , wherein the cooling step includes pouring the single-phase solution onto a spinning drum in order to form a ribbon, wherein the spinning drum is cooled.

7. The process of claim 1 , wherein the process for producing a primarily single-phase FCC, cobalt-chromium alloy including super saturated tungsten content comprises a physical vapor deposition process.

8. The process of claim 1 , wherein the solution comprises cobalt in an amount from about 30% to about 50% by weight of the solution.

9. The process of claim 1 , wherein the solution comprises nickel in an amount of about 10% by weight of the solution.

10. The process of claim 1 , wherein the solution is entirely free of molybdenum.

11. The process of claim 1 , wherein the cobalt-chromium alloy is substantially free of carbon.

12. The process of claim 1 , wherein the solution is entirely free of carbon.

13. The process of claim 1 , wherein the solution comprises no more than 1% of each of silicon, phosphorus, and sulfur by weight.

14. The process of claim 1 , wherein the solution further comprises manganese in a concentration up to 5% by weight of the solution.

15. The process of claim 1 , wherein the solution further comprises iron in a concentration up to 5% by weight of the solution.

16. The process of claim 1 , wherein the cobalt-chromium alloy further comprises both manganese and iron in a concentration of about 1.5% each, by weight.

17. The process of claim 1 , wherein a sum of cobalt and tungsten comprises from about 66 to 68% by weight of the cobalt-chromium alloy.

18. The process of claim 1 , wherein the solution is maintained at at least about 1500° C. for 1 minute to 30 minutes to ensure that the solution has sufficient time to reach an equilibrium state in which the single-phase FCC structure is attained.

19. The process of claim 1 , wherein a weight percent ratio of tungsten to cobalt is from 0.4 to 1.2.

20. A process for the production of a stent from a primarily single-phase FCC, cobalt-chromium alloy including tungsten, the process comprising:

forming a solution including cobalt, chromium, nickel and tungsten, the solution being entirely free of carbon and molybdenum and not including any other alloying elements in amounts greater than 3% by weight;

the tungsten being 25% to 30% by weight of the solution, so that the tungsten content is above a solubility limit of tungsten in the cobalt-chromium alloy at ambient temperature;

the nickel comprising about 10% by weight of the solution;

the chromium is 15% to 25% by weight of the solution;

heating the solution to a temperature of at least about 1300° C., and maintaining the solution at said temperature for a time period of at least 1 minute to ensure that the solution has sufficient time to reach an equilibrium state in which the single-phase FCC structure is attained; and

cooling the single-phase solution from at least 1300° C. to 500K at a rate of about 200° C./second to about 500° C./second within a period of time of less than 5 minutes to preserve a primarily single-phase FCC solid solution structure, even with the super-saturated tungsten content.

21. A process for the production of a single-phase FCC, cobalt-chromium alloy including tungsten, the process comprising:

forming a solid solution including cobalt, chromium, nickel and tungsten, the tungsten being 25% to about 35% by weight of the solid solution, so that the tungsten content is above a solubility limit of tungsten in the cobalt-chromium alloy at ambient temperature, the chromium is 15% to 25% by weight of the solution, wherein the solid solution is entirely free of carbon and molybdenum;

heating the solid solution to at least about 1300° C. for a time sufficient to form a single-phase solution;

cooling, without water quenching, the single-phase solution to 500K at a rate of about 200° C./second to about 500° C./second within a period of time of less than 10 minutes to preserve a single-phase FCC solid solution structure in a resultant alloy material, even with the super-saturated tungsten content;

heating the alloy material to at least 600° C. for at least 1 hour to form fine particulate Co 3 W while preserving the primarily single-phase FCC solid solution structure in the alloy material.