Score Resistance, Hardness and Performance of Diffused Copper-Nickel-Tin Bearings

Current production steel-back copper-lead bearings contain a nickel-barrier layer between the lead-tin babbitt overplate and copper-lead intermediate layer. When these bearings are used in heavy-duty engines the nickel-barrier layer changes composition via diffusion of tin into the nickel. When the journal wears through the thin babbitt into the modified nickel-barrier layer scoring distress occurs.

The copper-nickel-tin ternary system was studied. Its liquidus isothermal phase diagram was developed; intermetallic compounds were located; hardness and score resistance maps were generated; and the copper-nickel-lead-tin quaternary composition of actual field bearings as a function of depth through the barrier layer was examined.

A new tri-metal nickel-tin-copper barrier was developed which changes the composition of the barrier to have acceptable score resistance and hardness. An engine test in which coolant is added to the engine oil until scoring distress occurs was devised to simulate the distress encountered in service. The new tri-metal barrier bearing outperformed all other materials tested.