Geretsried, 17.10.205
Friction is both a blessing and a curse – on the one hand it provides the necessary grip between two contact surfaces, but on the other hand it is also responsible for wear, energy losses and temperature development in machines. In technology, it is therefore crucial to select specific material pairings in order to keep the sliding friction within a desired range.
Sliding pairs – i.e. material contacts that move against each other without rolling elements – can be found in numerous applications in mechanical and plant engineering. They can be found in joints, plain bearings, guides and also pump parts. The right choice of material pairing has a significant influence on service life, heat development and resistance to wear or scuffing, as well as the force required for sliding.
In general, sliding pairs are subject to forces and environmental conditions that can lead to various forms of wear:
- Adhesive wear (tendency to join similar materials, galling, cold welding)
- Abrasive wear (micro-cutting due to rough mating surfaces or smaller particles)
- Surface fatigue (due to dynamic or static loading at the strength limit)
- Corrosion wear (due to contact with corrosive media)
- Friction-induced heating
If a suitable material combination is not selected, material loss, failure due to blocking or overheating may occur. In particular, pairings of similar materials, e.g. identical metals, tend to seize and cold weld under load and in direct contact.
Such pairings are usually only reliable if constant lubrication is ensured or a specific surface coating has been applied.
Typical metallic sliding materials in mechanical engineering
Copper alloys such as bronzes, brass and aluminum bronzes (e.g. CuAl10Fe5Ni5) are among the most frequently used sliding materials in mechanical engineering as friction partners for steel.
| Material | Properties |
| Tin bronzes (CuSn) | Good wear resistance, good damping |
| Lead bronzes (CuPb) | Good emergency running properties, less load-bearing capacity |
| Brass (CuZn) | Cost-effective, limited mechanical load capacity |
| Aluminum bronze (CuAl) | High mechanical strength, low seizure tendency, very good corrosion resistance |
| Beryllium bronze (CuBe) | Very high strength and thermal conductivity, for high-performance applications |
Many of the plain bearing materials mentioned contain lead at >0.1% in order to improve emergency running properties, reduce wear and optimize running-in behaviour. However, the use of lead-containing alloys is increasingly being criticized, as lead is a toxic heavy metal that is harmful to both the environment and human health. Especially in applications with direct contact to drinking water, food or in open lubrication circuits, there is a risk of lead particles or ions being released. Stricter legal requirements – such as the European REACH Regulation, the Drinking Water Ordinance or RoHS – set tight limits and promote the switch to lead-free alternatives. This minimizes environmental impact, simplifies recycling processes and increases occupational safety without impairing the functionality of modern plain bearings.
ALBROMET GmbH specializes in the sale of hard bronzes and high-strength copper alloys and thus solves special requirements for sliding and guide elements in mechanical engineering. All alloys in the product portfolio are lead-free or have a lead content of <0.1%. The company offers semi-finished products from stock in a wide variety of shapes and dimensions, tailored to any required size. However, finished components such as plain bearings, guides and sliding plates are also manufactured from all alloys according to customer drawings.
A brief summary of the advantages of aluminum bronze:
- High strength and hardness
- Very good gliding behavior
- Good emergency running properties
- Low tendency to seize against steel and stainless steel
- Very good corrosion and seawater resistance
- Heat resistance up to approx. 300 °C
Aluminum bronze against steel: a proven pairing
The material combination of aluminum bronze (CuAl10Fe5Ni5 or similar alloys) against steel (e.g. C45 or hardened bearing steel 100Cr6) has proven itself in numerous industrial applications – especially where high mechanical loads, corrosion requirements and wear resistance are required. But why does this pairing work so well?
Different hardships – but with caution
Aluminum bronze is softer than hardened steel and also slightly softer than stainless steel. In this friction pairing, the softer material (in this case the aluminum bronze) wears down and thus protects the steel counterpart. This targeted “sacrificial strategy” extends the service life of the steel and maintains the function of the assembly. For this reason, the softer material is chosen for the simpler component or the part that can be easily replaced.
Low tendency to cold welding
With similar materials (e.g. steel against steel), the components can literally stick together under pressure and friction – tendency to cold welding. When aluminum bronze is paired with steel, the different chemical composition reduces the tendency towards adhesive friction.
Friction coefficient µ under control
Depending on the surface roughness and lubrication, the coefficient of sliding friction µ of this pairing is typically between 0.15 and 0.25 in the lubricated state – a favorable range for many technical applications. Without lubrication, the coefficient of friction increases, but often remains within the controllable range (approx. 0.4-0.6), which gives the pairing a certain emergency running characteristic.
Corrosion and temperature resistance
Aluminum bronze offers excellent corrosion resistance – a clear advantage over other copper alloys and steels. Only at elevated temperatures above 300 °C does the friction behavior deteriorate. Aluminum bronze is also stable in water and does not tend to dezincify, as can be the case with brass.
Compatibility with lubricants or suitability for dry running
Aluminum bronze is very compatible with many commercially available lubricants. Due to its low coefficient of friction when paired with steel, it also has good emergency running properties if lubrication fails for a short time or if heating occurs.
Aluminum bronze can also be found in rolling bearings in particularly demanding applications such as seawater pumps, high-speed machine bearings or bearings in the food and chemical industries, where corrosion is critical. It is then used as a friction partner for the hardened steel balls or rollers as a material for the bearing cage or as a thrust ring in hybrid bearings.
Typical material pairings in practice practice
| Component A | Component B | Rating |
| Stainless steel, steel | Aluminum bronze | Very good sliding pairing, low tendency to seize, high loads possible |
| Stainless steel, steel | Pewter bronze | Good for moderate loads |
| Stainless steel, steel | Plastics (e.g. PEEK, PTFE) | For dry-running, lower loads |
| Stainless steel, steel | Stainless steel, steel | Only suitable to a limited extent – risk of scuffing, coating or permanent lubrication required |
| Hardened steel | Aluminum bronze | Heavy-duty, good service life |
Conclusion
The right combination of materials is crucial for durable, low-wear sliding pairs. While similar metals can be problematic, copper alloys – especially aluminum bronzes – offer a proven solution as a mating partner to steel or stainless steel. Their good tribological properties, combined with high corrosion and temperature resistance, make them a universally applicable group of materials in demanding applications. Due to their chemical composition, they are certified for use in direct contact with food from a pH value greater than 4.5. This means that the aluminum bronzes can also be used in food processing and packaging machines without any problems. At the same time, they are free of lead and other substances on the SVHC list and therefore RoHS and REACH compliant.
The technical article was published on 02.10.2025 in the Industrieanzeiger, click here for the article.
