Development of a Stainless Corrosion Resistant Carburizing Bearing Steel

The development of a stainless corrosion resistant carburizing bearing steel by Carpenter Technology Corporation is detailed. The alloy, Carpenter VIM-VAR Pyrowear^® 675 Stainless alloy, has corrosion resistance equivalent to Type 440C stainless, combined with fracture toughness superior to any martensitic stainless steel and equivalent if not superior to normal noncorrosion resistant carburizing bearing steels such as SAE Type 8620 or 9310.

The discussion will include case and core properties, and carburizing techniques employed to optimize case structures.

The alloy is capable of maintaining a case hardness of HRC 59 at 329°C (625°F). This capability, along with superior fracture toughness compared to both the currently used M50 and the newly developed M50NiL, makes it a viable candidate for main shaft bearings for turbojet engines.