MAHLE bearings: robust and durable

Many renowned engine manufacturers develop and test their aggregates together with MAHLE in order to benefit from decades of bearing experience. These bearings are used on valve rocker shafts, camshafts, conrods, crankshafts, and balancer shafts in combustion engines. MAHLE is continuously developing materials and production technologies and manufactures bearing shells and thrust washers with diameters from 27 to 140 mm and bushings from 6 to 105 mm. Naturally at the highest quality, even for the aftermarket.

The demands on our bearings are pretty tough

Combustion engines continue to advance and specific engine output is still rising. Diesel engines now reach ignition pressures of well over 200 bar. Direct-injection diesel engines produce surface pressures in the bearings of up to 120 N/mm.2At the same time, installed size is decreasing—including the dimensions of the bearings. Oil change intervals are also becoming increasingly longer for new engine designs. Because the bearings also need to bind tiny wear particles from the engine oil, this is an additional load. It is understandable that this is too much to ask of traditional materials. Modern engines require bearing materials with much higher fatigue resistance and lower wear rates, especially in the mixed-friction range. At the same time, good corrosion resistance must also be ensured at higher temperatures.

The material bearings are made of

Materials: for the safety of people, engines, and the environment—only the best

Strength, good interference fit, good running properties—these are conflicting material requirements. The solution: multilayer bearings, constructed according to the principle of division of labour.

In principle, there are three types of bearings: solid bearings made of one metal, two-component bearings made of two materials, and three-component bearings made of—you guessed it—a combination of three metals. Bearings made of several materials almost always consist of a high-strength steel support shell coated with various bearing metals. The materials are selected to ensure that the positive properties complement each other and the combination is optimal for the application considered. Material development also plays a key role. The design and thickness of the metal layers also influence all the properties of the bearing. With years of experience, MAHLE can offer a great variety of high-quality alloys (including aluminium and bronze).


Solid bearings
they consist of one bearing metal, made from special alloys.


Two-component bearings
the steel support shell is supplemented by an intermediate layer and a layer of bearing metal—for low to medium engine loads.


Three-component bearings
they consist of a steel support shell, a bearing layer, barrier layer, and an overlay (as sputter bearings with special coatings)—used in highly turbocharged engines, for example.


Super resistant—the sputter bearing

Sputter bearings have been used in powerful diesel and petrol engines for several years. But what is sputtering, actually?

In the sputtering process, the bearing shells, consisting of the steel support, the bearing layer, and the barrier layer, are placed in the vacuum of the sputtering machine. Cathode anodisation is used to apply the overlay material to the bearing shells. This produces the extremely hard and wear-resistant overlay of the bearing shells.

1 Cathode
2 Argon feed (plasma gas)
3 Ion flow
4 Atomic material flow (dispersion)
5 Plasma
6 Bearing shells
7 Vacuum pump
8 Electrical power

A vacuum chamber with a small quantity of noble gas contains three things: a positively charged anode, a negatively charged cathode that has a metal coating—and the three-component bearing to be sputtered. A high voltage is applied between the anode and the cathode. The electrons are ripped away from the cathode and launched towards the anode. Along the way they ionise the noble gas atoms. The now positively charged noble gas atoms fly to the cathode and knock atoms out of the metal coating that surrounds the cathode. Secondary electrons are also released, which in turn ionise additional noble gas atoms. This produces a mixture of free electrons, positive ions, and neutral noble gas particles, known as a static plasma. The neutral atoms knocked out of the cathode metal layer then condense as a thin, extremely resistant metal coating on the bearing overlay. The smaller particle size gives the layer thus generated remarkable hardness, high elastic limit, and excellent wear properties.

The extreme hardness of the sputter coating prevents any engine oil contaminants from being picked up. As a result, a sputtered bearing shell is always combined with a softer three-component bearing. This embeds the dirt particles in its galvanized bearing layer—rendering them harmless to the engine. In order to identify the sputtered half of the bearing, MAHLE imprints them with the word “SPUTTER” on the back. This guarantees correct installation—because the correct installation orientation of the sputtered bearing shell is critical to the reliable function and service life of the bearing.

Sputter bearing from MAHLE with identification

Research and development for the repair shop: so that you can continue to install safe products in the future

Innovative development: polymer coating

Not exactly new, but completely up-to-date, polymer-coated bearing shells and thrust washers are up to 15 times more wear-resistant than the variant without this coating. The polymer coating primarily benefits the new measures for reducing CO2, such as hybridisation, start-stop or sailing mode, and turbocharging. This is because polymers prevent the high engine-internal wear that these technologies would otherwise cause.

The polymer layer contains homogeneously distributed metal particles oriented in the running direction. MAHLE applies this type of layer to aluminium substrates, cast or sintered bronze alloys, and aluminium-tin sputter coatings. The result is bearing shells and thrust washers that can handle smaller oil pumps and low-viscosity engine oils.

+

Polymer-coated bearing shells