MP35N cobalt-nickel-chrome-molybdenum alloy (Gaylord Smith / International Nickel)

Tom's "favorite alloy." 35Co-35Ni-20Cr-10Mo, developed by Gaylord Smith at International Nickel in the 1960s. Non-magnetic, strengthens by twinning under cold work, reaches 280 ksi yield as bolt stock. Four MP35N bolts hold the 747 wing onto the fuselage. ASTM-specced for surgical implants since 1978.

As I looked at this, I thought, what are these guys doing — they're just looking at one of my favorite alloys, MP35N. MP35N has been around since probably the 1960s. A guy named Gaylord Smith at International Nickel came up with a four-component system which was basically chromium, nickel, molybdenum, cobalt. All they did is they threw some iron in there. It's a cobalt alloy — cobalt's kind of expensive. Molybdenum is about thirty for both of these, about twenty for chromium. So it's sort of a nickel-chromium-cobalt steel with some aluminum, but it's a very interesting material.