Molybdenum Endoprostheses

Abstract

An endoprosthesis can have a member that includes molybdenum and at least one metal selected from the group consisting of titanium, rhenium, yttrium, palladium, rhodium, ruthenium, tungsten, tantalum, iridium, zirconium, hafnium, niobium, chromium, and combinations thereof. The member can have a microstructure characterized by: (a) a molybdenum-rich base region comprising at least 50 weight percent molybdenum, (b) a surface region comprising at least one metal selected from the group consisting of titanium, rhenium, yttrium, palladium, rhodium, ruthenium, tungsten, tantalum, iridium, zirconium, hafnium, niobium, chromium, and combinations thereof, and (c) an inter-diffusion region in which the concentration of molybdenum decreases in the thickness direction from the molybdenum-rich base region to the surface region of the member.

What is claimed is: 
     
         1 . An endoprosthesis comprising a member that includes molybdenum and at least one metal selected from the group consisting of titanium, rhenium, yttrium, palladium, rhodium, ruthenium, tungsten, tantalum, iridium, zirconium, hafnium, niobium, chromium, and combinations thereof,
 the member having a microstructure characterized by:
 (a) a molybdenum-rich base region comprising at least 50 weight percent molybdenum, 
 (b) a surface region comprising at least one metal selected from the group consisting of titanium, rhenium, yttrium, palladium, rhodium, ruthenium, tungsten, tantalum, iridium, zirconium, hafnium, niobium, chromium, and combinations thereof, and 
 (c) an inter-diffusion region in which the concentration of molybdenum decreases in the thickness direction from the molybdenum-rich base region to the surface region of the member. 
   
     
     
         2 . The endoprosthesis of  claim 1 , wherein the molybdenum-rich base region comprises no more than 10 weight percent of any of the following elements: titanium, rhenium, yttrium, palladium, rhodium, ruthenium, tungsten, tantalum, zirconium, hafnium, iridium, and chromium. 
     
     
         3 . The endoprosthesis of  claim 1 , wherein the member has a modulus of between 44 and 50 msi. 
     
     
         4 . The endoprosthesis of  claim 1 , wherein the member has a 0.2% offset yield strength of at least 50 ksi. 
     
     
         5 . The endoprosthesis of  claim 1 , wherein the member has an elongation to break of at least about 15%. 
     
     
         6 . The endoprosthesis of  claim 1 , wherein the molybdenum-rich base region has a density of at least 9.5 g/cc. 
     
     
         7 . The endoprosthesis of  claim 1 , wherein the molybdenum-rich base region comprises at least 95 weight percent molybdenum. 
     
     
         8 . The endoprosthesis of  claim 7 , wherein the molybdenum-rich base region comprises 1.25 weight percent titanium, 0.3 weight percent zirconium, 0.15 weight percent carbon, and a balance of molybdenum. 
     
     
         9 . The endoprosthesis of  claim 7 , wherein the molybdenum-rich base region comprises between 0.25 and 1.0 weight percent titanium, between 0.04 and 2.0 weight percent zirconium, between 0.01 and 0.04 weight percent carbon, and a balance of molybdenum. 
     
     
         10 . The endoprosthesis of  claim 7 , wherein the molybdenum-rich base region comprises 99.95% pure molybdenum doped with potassium silicate. 
     
     
         11 . The endoprosthesis of  claim 1 , wherein the surface region is essentially free of molybdenum. 
     
     
         12 . The endoprosthesis of  claim 1 , wherein the surface region comprises less than 50 percent by weight molybdenum. 
     
     
         13 . The endoprosthesis of  claim 1 , wherein the surface region comprises titanium. 
     
     
         14 . The endoprosthesis of  claim 1 , wherein the surface region comprises a titanium-molybdenum alloy. 
     
     
         15 . The endoprosthesis of  claim 1 , wherein the surface region consists essentially of titanium. 
     
     
         16 . The endoprosthesis of  claim 1 , wherein the inter-diffusion region is between 10 nanometers and 10 microns thick. 
     
     
         17 . The endoprosthesis of  claim 1 , wherein the inter-diffusion region is at least 1 micron thick. 
     
     
         18 . The endoprosthesis of  claim 1 , wherein the inter-diffusion region comprises iridium. 
     
     
         19 . The endoprosthesis of  claim 18 , wherein the inter-diffusion region comprises a higher concentration of iridium than either the molybdenum-rich base region or the surface region. 
     
     
         20 . The endoprosthesis of  claim 1 , wherein the member further comprises oxides, carbides, nitrides, or a combination thereof overlying the surface region.