Page 6 - Dana Glacier Bearings Materials Brochure, designed and produced by Connell Marketing Associates, UK

Bearing Material Groups

Overlay Materials
Some bi-metals, depending on the application, are overlay plated to improve their soft
phase properties. An overlay plated bi-metal bearing is referred to as a tri-metal bearing.
An overlay consists of a thin surface layer (up to 0.040mm thick) which is precision
electroplated onto the bi-metal surface after finish boring.

Bearing Overlay Materials

PbIn PbSnCu PbSnAl203 Sputter AlSn

Page - 6 The overlay is supplied in a range of thicknesses in order to achieve the desired balance of
properties. Thinner overlays promote a higher load carrying capacity, while thicker overlays
provide greater conformability and embeddability. A range of overlays is available, some with
a nickel interlayer, on both aluminium silicon and lead bronze substrates.

Lead-Indium Composite Overlays Sputtered Overlays
Lead-bronze is overlay plated with A composite overlay contains two One viable alternative to electro-
lead-indium by successively or more constituents which act plating is the use of sputtering.
electro-plating with lead, then with synergistically to provide both Glacier Vandervell has selected
indium. The indium is diffused physical and mechanical properties aluminium - 40% tin overlay due to
through the lead and into the lead unobtainable from the individual its proven quality as a bearing
pools of the bronze substrate so that constituents alone. Electroplating material. The structure of the overlay
the corrosion protection provided by has proven to be the most promising consists of an even distribution of tin
the indium is retained should the of all the techniques available for in an aluminium matrix.
overlay be removed in service. composite manufacture.
The aluminium - 40% tin overlay
Lead-Tin-Copper Lead-tin-alumina is Glacier exhibits superior mechanical
Lead-tin-copper is an alternative Vandervell’s first composite overlay. strength properties over
overlay to lead-indium. It lacks the conventional electro-plated lead
fatigue strength of lead-indium but Alumina powder is suspended in a alloys and is used with cast lead-
has better wear resistance. lead-tin fluoroborate solution and the bronze for the most arduous long
processing parameters manipulated life applications.
This overlay is electrolytically to produce deposits containing from
co-deposited onto the substrate 0.5 to 2.0% alumina with 10% tin.
and requires a nickel interlayer to Co-deposition is dependent upon
prevent diffusion of the tin into the obtaining a satisfactory suspension
lead-bronze which would reduce of the inert particles in the solution.
the overlay corrosion resistance.
Sapphire fatigue machine tests show
Lead-Tin a small but useful improvement in
Lead-tin overlay is co-deposited strength over standard overlays.
onto the lead-bronze and offers a Furthermore, the presence of
good compromise of properties. alumina in the overlay doubles wear
resistance when compared with
lead-tin-copper and more than
trebles when compared with lead-
indium.