Abstract

Cobalt chromium molybdenum (CoCrMo) has many material properties that make it desirable as a medical hip implant. Due to the range of heat treatments available and the resulting material properties that are present in medical device manufacturing using CoCrMo, many implants are not able to withstand both the chemical and physical wear necessary as a hip replacement. This research looks to examine various heat treatments and their resulting properties to find a desirable heat treatment for CoCrMo in hip implant bearing surfaces. This study was accomplished by using five distinct variations of heat treatment on forged CoCrMo alloy that would be used in medical device manufacture. After heat treatment, microstructure analysis, hardness measurements, and tribological and corrosive wear tests were performed. Tribological tests were performed using a pin on disk wear test for two million cycles, while corrosion testing was performed using a potentiostat and 3-electrode-cell in bovine serum to simulate conditions in the body. Grain structure and composition were reviewed for each sample by using X-ray analysis and electron backscatter diffraction (EBSD) microscopy. From this, we could determine the grain size, orientation, and phase composition that would result in the different physical and chemical properties. This research shows that a solution heat treatment induces a change towards an FCC grain structure, that an aging treatment creates an HCP grain structure, and that while the untreated forged sample showed high wear resistance, a cyclically treated sample is highly resistant to both physical wear and corrosion. These observations can be attributed to the phase content, grain size, structure, and grain boundary misorientation that influence the characteristics of the implant material from the microstructure level.

Degree

College and Department

Ira A. Fulton College of Engineering; Manufacturing Engineering

Rights

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