Dr. Dmitri Kopeliovich
Sputter overlays are deposited by Sputtering method (Physical Vapor Deposition (PVD)).
Sputtering utilizes argon ions for bombarding a cathodically connected target, made of the coating material (normally Al20Sn or Al40Sn).
Sputtering method provide extremely homogeneous distribution of tin within aluminum matrix. Hardness of aluminum-tin sputter material is about 90 HV, which is three times higher than hardness of aluminum-tin alloy prepared by conventional methods (casting).
Cast copper based bearings or high strength aluminum based bearings are commonly plated by sputter overlays.
Load carrying capacity of sputter bearings is highest of all bearing materials: 14500-17400 psi (100-120 MPa).
The disadvantages of sputter bearings: high production cost (slow deposition process) and poor soft anti-friction properties (compatibility, conformability, embedability).
Improvement of anti-friction properties and cost reduction are achieved by a combination of a sputter bearing shell in the high load position (conrod) with a common tri-metal bearing shell in the less loaded position (cap).
Sputter bearings are mainly used as connecting rod bearings in highly loaded diesel engines with direct fuel injection system.