High strength member for intracorporeal use

Abstract

This invention is directed to an intracorporeal device formed of a high strength Co—Ni—Cr alloy and is particularly suitable for forming a composite product with a pseudoelastic member formed of NiTi alloy. Suitable intracorporeal products include guidewires and stents. The high strength alloy consists essentially of about 28 to about 65% cobalt, about 2 to about 40% nickel, about 5 to about 35% chromium, up to about 12% molybdenum, up to about 20% tungsten, up to about 20% iron and the balance inconsequential amounts of impurities and other alloying constituents, with a preferred alloy composition including about 30 to about 45% cobalt, about 25 to about 37% nickel, about 15 to about 25% chromium and about 5 to about 15% molybdenum. Intravascular devices such as guidewires, stents and the like can be formed of this high strength Co—Ni—Cr alloy.

What is claimed:  
     
         1 . A method for making a stent, comprising: 
 forming cylindrical elements with undulating components from an alloy material containing at least 2 weight percent each of cobalt, chromium, and nickel, the cylindrical elements generally aligned along a common longitudinal axis and interconnected;    electrochemically polishing the cylindrical elements, thereby forming a stent, the stent being plastically deformable to expand from a first diameter to a second larger diameter suitable for holding open a blood vessel.    
     
     
         2 . The method according to  claim 1  further comprising forming the cylindrical elements from a tubing of an alloy that has been cold-worked.  
     
     
         3 . The method according to  claim 2  wherein the alloy has been age-hardened.  
     
     
         4 . The method according to  claim 2  further comprising chemically treating the tubing.  
     
     
         5 . The method according to  claim 2  wherein the alloy contains about 28 to about 65 weight percent cobalt, about 5 to about 35 weight percent chromium, about 2 to about 40 weight percent nickel.  
     
     
         6 . The method according to  claim 5  wherein the alloy further contains up to 12 weight percent molybdenum.  
     
     
         7 . The method according to  claim 5  wherein the alloy further contains up to 20 weight percent tungsten.  
     
     
         8 . The method according to  claim 5  further comprising using a laser to form a pattern of the undulating components.  
     
     
         9 . The method according to  claim 8  further comprising applying a coating on the tubing and forming a pattern of the undulating components with laser irradiation.  
     
     
         10 . The method according to  claim 5  further comprising applying a photoresist coating on the tubing and exposing a pattern of the undulating components by ablating photoresist with laser irradiation  
     
     
         11 . The method according to  claim 1  further comprising applying a biocompatible coating on the electrochemically polished cylindrical elements.  
     
     
         12 . A method for making a stent, comprising: 
 forming cylindrical elements with undulating components from tubing of an alloy containing about 28 to about 65 weight percent cobalt, about 5 to about 35 weight percent chromium, about 2 to about 40 weight percent nickel, the undulating components have a relatively flat cross section and are arranged such that they are generally aligned along a common longitudinal axis and interconnected;    electrochemically polishing the cylindrical elements, thereby forming a stent, the stent being plastically deformable to expand from a first diameter to a second larger diameter suitable for holding open a blood vessel.    
     
     
         13 . The method according to  claim 12  wherein the alloy further contains up to 12 weight percent molybdenum.  
     
     
         14 . The method according to  claim 12  wherein the alloy further contains up to 20 weight percent tungsten.  
     
     
         15 . The method according to  claim 12  further comprising using a laser to form a pattern of the undulating components.  
     
     
         16 . The method according to  claim 12  further comprising applying a biocompatible coating on the electrochemically polished cylindrical elements.  
     
     
         17 . The method according to  claim 12  wherein at least one of the cylindrical elements is arranged out of phase with at least another one of the cylindrical elements.  
     
     
         18 . The method according to  claim 12  wherein at least one of the cylindrical elements is arranged in-phase with at least another one of the cylindrical elements.  
     
     
         19 . The method according to  claim 12  wherein the cross-section of the undulating component of the cylindrical element has an aspect ratio of about two to one.  
     
     
         20 . The method according to  claim 12  wherein the cross-section of the undulating component of the cylindrical element has a height-to-width aspect ratio of about two to one to about 0.5 to one.  
     
     
         21 . A method for making a stent, comprising: 
 forming cylindrical elements with undulating components from tubing of an alloy containing about 28 to about 65 weight percent cobalt, the alloy further containing chromium and nickel, and at least one element from the group consisting of molybdenum and tungsten, wherein the undulating components have a relatively flat cross section and the cylindrical elements are arranged such that the cylindrical elements are generally aligned along a common longitudinal axis and interconnected;    electrochemically polishing the cylindrical elements, thereby forming a stent plastically deformable to expand from a first diameter to a second larger diameter suitable for maintaining the patency of a blood vessel.    
     
     
         22 . The method according to  claim 21  wherein the alloy further contains up to 12 weight percent molybdenum.  
     
     
         23 . The method according to  claim 21  wherein the alloy further contains up to 20 weight percent tungsten.  
     
     
         24 . The method according to  claim 21  wherein the alloy further contains about 5 to about 35 weight percent chromium, and about 2 to about 40 weight percent nickel.  
     
     
         25 . The method according to  claim 21  further comprising using a laser to form a pattern of the undulating components.  
     
     
         26 . The method according to  claim 21  further comprising applying a biocompatible coating on the electrochemically polished cylindrical elements.  
     
     
         27 . The method according to  claim 21  wherein at least one of the cylindrical elements is arranged out of phase with at least another one of the cylindrical elements.  
     
     
         28 . The method according to  claim 21  wherein at least one of the cylindrical elements is arranged in-phase with at least another one of the cylindrical elements.  
     
     
         29 . The method according to  claim 21  wherein the cross-section of the undulating component of the cylindrical element has an aspect ratio of about one to one.  
     
     
         30 . The method according to  claim 21  wherein the cross-section of the undulating component of the cylindrical element has an aspect ratio of about two to one.  
     
     
         31 . The method according to  claim 21  wherein the cross-section of the undulating component of the cylindrical element has a height-to-width aspect ratio of about two to one to about 0.5 to one.