The effect of porous coating processing on the corrosion behavior of cast Co–Cr–Mo surgical implant alloys

✍ Scribed by Dr. J. J. Jacobs; R. M. Latanision; R. M. Rose; S. J. Veeck

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 795 KB
• Volume: 8
• Category: Article
• ISSN: 0736-0266
• DOI: 10.1002/jor.1100080613

✦ Synopsis

Abstract

The manufacture of porous coated cobalt‐based surgical implant alloys requires sintering–a high temperature process above the incipient melting temperature of this alloy system. The metallurgical changes produced by the high temperature sinter cycle consist of dissolution of interdendritic carbides, massive precipitation of lamellar carbide eutectic phases at grain boundaries, localized porosity from incipient melting that is not completely eliminated by subsequent hot isostatic pressing, and grain growth in fine‐grained meterials. These microstructural changes, which are known to affect the mechanical properties, do not affect the static in vitro localized and generalized corrosion behavior of the bulk material as determined by anodic polarization measurements in a buffered saline environment and direct examination by scanning electron and optical microscopy. Additionally, cast Co‐Cr‐Mo surgical implant alloys are found to be immune to crevice corrosion (in the absence of mechanical fretting) in the saline environment studied. The hystertic component of the anodic polarization curve is not due to crevice corrosion; rather, as suggested by the electrochemical tests and Auger spectroscopy, the hysteresis is due to redox reactions in the chromium‐rich surface layer.