Aerospace Fasteners: A286 vs. MP35N Fatigue Resistance

 

Why A286 dominates jet engine bolting?
A286 maintains 130 ksi tensile strength at 700°C via gamma prime hardening. CTE matches nickel superalloys, preventing joint loosening during thermal cycling. Proven in 50,000+ flight hours.

 

When is MP35N preferred for landing gear?
For components requiring 260 ksi yield strength and infinite fatigue life. MP35N's corrosion fatigue strength exceeds A286 by 300% in salt spray. Mandatory for carrier-based aircraft.

 

Hydrogen embrittlement risks?
A286 susceptible above 0.5 ppm dissolved hydrogen. Requires vacuum melting and baking. MP35N immune due to FCC structure. Both require <1 HRC hardness variation.

 

Optimal heat treatment?
A286: Solution treat 980°C/1hr → Age 720°C/16hrs.
MP35N: Cold work 50% → Age 540°C/4hrs.
Non-uniform aging causes 40% strength loss.

 

NDE requirements?
100% magnetic particle inspection per AMS 2301. Lot traceability to melt certification. Hydrogen content <0.3 ppm. Surface roughness Ra <0.8 μm.