What are the metallurgical implications of using Elgiloy (Co-Cr-Ni-Mo) for medical implant wave springs?

Elgiloy (complying with ASTM F1058) is chosen for medical implants due to its extreme biocompatibility, fatigue resistance, and corrosion resistance. Metallurgically, it is a cobalt-based alloy that achieves its properties through a combination of cold work and age hardening. It is non-magnetic, which is vital for MRI compatibility. The fatigue strength of Elgiloy is roughly 30% higher than 316L stainless steel, allowing for smaller, thinner wave springs in applications like cardiac valves or orthopedic implants. The aging process (typically 5 hours at 480°C) optimizes the precipitate distribution, providing a yield strength exceeding 1900 MPa.