Sintered Bronze Bearing Material Properties

October 26, 2018

Based on powder metallurgy technology, sintered bronze bearings deliver a very familiar feature. That opening sentence is, of course, referring to the material’s porous build. Friction counteracting lubricants are stored inside the metal’s tiny chambers. Okay, so this general property gets mentioned in every article, because that’s what the bearings do best, but there’s more to this technology than that self-lubricating feature.

Bronze-Elevated Sintering Features 

Made from copper, the metal is infused with a measured quantity of tin. Around 10% of the alloy is tin, so the remaining 90% is copper. Furthermore, the alloy is readily available, so it’s not an expensive blend. Just the opposite, bronze is a popular fabrication metal. Used for statues, sculptures, contacts in electrical circuits, and the plumbing profession, the orange-brown metal is found in countless applications. But those typical usage areas rely on cast metals, on extruded and rolled bronze. For bronze bearings, the sintering process replaces clumsy castings. Bearings made of sintered bronze feature the following invaluable material properties:

  • Self-lubricating
  • Corrosion resistant
  • Enhanced workability
  • Popular in marine applications
  • Durable and fatigue resistant

Improving Bronze Bearings 

This material and its self-lubricating properties have been described in detail before. We know the metal thrives in marine components. We also know bronze bearings encourage capillary action, so an oily film forms quickly, pretty much as soon as a bearing spins up to speed. Having covered the advantages, let’s save a mention for a single drawback. If a shafted machine isn’t used often, it starts erratically, or it’s bogged down by a heavy load, then sintered bearings can run into trouble. To offset such problems, sintering engineers use higher material porosity values, special substrate bonding processes, and advanced lubricants. Sure, an older generation bronze bushing may emit a squeal of protest when a shaft starts to rotate, but these advanced-design bronze bearings handle infrequent usage patterns quite well, all thanks to bronze’s innate material properties.

It’s a balancing act, like any other engineering process. Higher porosity bronze, perhaps as a high as 40% oil-permeable, is obviously achievable, but a stronger alloy will be needed to offset the weaker structural build. Alternatively, bearing designers often opt for thicker bronze bushings, but this option only works in an application that can afford the additional space. Finally, just to bolster this rust and fatigue resistant alloy further, some manufacturers have decided to fuse bronze, to bind it to layers of load-supporting steel. With this last feature in mind, expect composite bronze bushings to take their place in heavier industrial applications.

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