Quaternary cobalt-nickel-chromium-molybdenum fatigue resistant alloy for intravascular medical devices

Abstract

A biocompatible solid-solution alloy may be formed into any number of implantable medical devices. The solid-solution alloy comprises a combination of elements in specific ratios that improve its fatigue resistance while retaining the characteristics required for implantable medical devices. The biocompatible solid-solution alloy is a quaternary cobalt-nickel-chromium-molydenum alloy having substantially reduced titanium content.

1 . A biocompatible, load-carrying metallic structure being formed from a solid-solution alloy comprising nickel in the range from about 33 weight percent to about 37 weight percent, chromium in the range from about 19 weight percent to about 21 weight percent, molybdenum in the range from about 9 weight percent to about 11 weight percent, iron in the range from about 0 weight percent to about 1 weight percent, manganese in the range from about 0 weight percent to about 0.15 weight percent, silicon in the range from about 0 weight percent to about 0.15 weight percent, carbon in the range from about 0 to about 0.025 weight percent, phosphorous in the range from about 0 to about 0.015 weight percent, boron in the range from about 0 to about 0.015 weight percent, sulfur in the range from about 0 to about 0.010 weight percent, titanium in an amount not to exceed 0.015 weight percent and the remainder cobalt.  
   
   
       2 . The biocompatible, load-carrying metallic structure according to  claim 1 , wherein the solid-solution alloy is constructed through thermomechanical processing to exhibit relatively high strength and low ductility characteristics in the fully cold-worked state.  
   
   
       3 . The biocompatible, load-carrying metallic structure according to  claim 1 , wherein the solid-solution alloy is constructed through thermomechanical processing to exhibit relatively moderate strength and moderate ductility characteristics in the partially cold-worked state.  
   
   
       4 . The biocompatible, load-carrying metallic structure according to  claim 1 , wherein the solid-solution alloy is further constructed through age hardening for a predetermined time within a gaseous environment at a temperature less than the annealing temperature to precipitate one or more secondary phases, including at least one of intragranular and intergranular phases, from a substantially single phase structure.  
   
   
       5 . The biocompatible, load-carrying metallic structure according to  claim 4 , wherein the age hardening temperature is in the range from about 1,000 degrees Fahrenheit to about 1,950 degrees Fahrenheit.  
   
   
       6 . The biocompatible, load-carrying metallic structure according to  claim 4 , wherein the age hardening gaseous environment comprises hydrogen, nitrogen, argon and air.  
   
   
       7 . The biocompatible, load-carrying metallic structure according to  claim 3 , wherein the solid-solution alloy is further constructed through stress relieving for a predetermined time within a gaseous environment at a temperature less than the annealing temperature while maintaining a substantially single phase to increase toughness and ductility.  
   
   
       8 . The biocompatible, load-carrying metallic structure according to  claim 7 , wherein the stress relieving temperature is about or less than 100 degrees Fahrenheit below the annealing temperature.  
   
   
       9 . The biocompatible, load-carrying metallic structure according to  claim 7 , wherein the stress relieving gaseous environment comprises hydrogen, nitrogen, argon and air.  
   
   
       10 . The biocompatible, load-carrying metallic structure according to  claim 1 , wherein the solid-solution alloy is constructed through thermomechanical processing to exhibit relatively low strength and high ductility characteristics in the fully annealed state.  
   
   
       11 . The biocompatible, load-carrying metallic structure according to  claim 1 , wherein the medical device comprises a fixation device.  
   
   
       12 . The biocompatible, load-carrying metallic structure according to  claim 1 , wherein the medical device comprises an artificial joint implant.  
   
   
       13 . The biocompatible, load-carrying metallic structure according to  claim 3 , wherein the solid-solution alloy is further constructed through stress relieving for a predetermined time with a vacuum environment at a temperature less than the annealing temperature while maintaining a substantially single phase to increase toughness and ductility.  
   
   
       14 . The biocompatible, load-carrying metallic structure according to  claim 13 , wherein the stress relieving temperature is about or less than 100 degrees Fahrenheit below the annealing temperature.