Official Answer
Answer
MP35N is a multiphase alloy (Ni-Co-Cr-Mo) that offers a unique combination of ultra-high strength (up to 300 ksi tensile) and excellent biocompatibility. Compared to 316L, MP35N has a much higher fatigue limit and modulus of elasticity. In medical devices like heart valves or orthopedic implants where the spring must be tiny yet powerful, MP35N allows for extreme miniaturization. 316L is often too soft ($S_y \approx 40$ ksi annealed) to function as a high-performance spring without excessive bulk. Furthermore, MP35N is highly resistant to crevice corrosion and pitting in saline body fluids, where 316L might fail over long durations.
