Official Answer
Answer
MP35N (UNS R30035) is a multi-phase alloy (Ni-Co-Cr-Mo) known for its ultra-high strength ($S_{ut}$ up to $2000$ MPa) and exceptional fatigue life. In racing engines, retaining rings are subjected to extreme vibrations and temperatures. MP35N's high modulus ($E \approx 233$ GPa) and resistance to 'thermal relaxation' make it ideal for wrist pin retention or oil pump assemblies. The material is hardened through cold work and subsequent aging at $538^\circ C$. This results in a ring that can withstand high centrifugal forces and rapid thermal cycling without losing its 'grip' on the shaft.
