Jacobs J J, Latanision R M, Rose R M, Veeck S J
Harvard Combined Orthopaedic Residency Program, Boston, Massachusetts.
J Orthop Res. 1990 Nov;8(6):874-82. doi: 10.1002/jor.1100080613.
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.
多孔涂层钴基外科植入合金的制造需要烧结，这是一个高于该合金体系初始熔化温度的高温过程。高温烧结循环产生的冶金变化包括枝晶间碳化物的溶解、晶界处片状碳化物共晶相的大量析出、初始熔化产生的局部孔隙（随后的热等静压不能完全消除）以及细晶粒材料中的晶粒长大。这些已知会影响力学性能的微观结构变化，并不影响在缓冲盐水环境中通过阳极极化测量以及扫描电子显微镜和光学显微镜直接检查所确定的块状材料的静态体外局部和全面腐蚀行为。此外，在所研究的盐水环境中，铸造钴铬钼外科植入合金被发现对缝隙腐蚀（在没有机械微动的情况下）具有免疫力。阳极极化曲线的滞后部分并非由于缝隙腐蚀；相反，正如电化学测试和俄歇能谱所表明的，滞后是由于富铬表面层中的氧化还原反应。
