The effect of porous coating processing on the corrosion behavior of cast Co-Cr-Mo surgical implant alloys.
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 materials. 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 hysteretic 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.
Harvard Combined Orthopaedic Residency Program, Boston, Massachusetts.
J J
JJ
Jacobs
R M
RM
Latanision
R M
RM
Rose
S J
SJ
Veeck
D001842:Bone and Bones; D002858:Chromium Alloys / Q000737:chemistry*; D004563:Electrochemistry; D008422:Materials Testing; D008669:Metallurgy / Q000379:methods; D008855:Microscopy, Electron, Scanning; D008982:Molybdenum; D019736:Prostheses and Implants; D013499:Surface Properties
D002858:Chromium Alloys; D008982:Molybdenum