Solving Engine Bearing Fatigue Failures with Silver Based Materials
One of the most important engine bearing properties is fatigue strength. Fatigue cracks start on the surface and then penetrate into the material. All layers of a multilayer bearing material must have fatigue strength that is greater than the actual load applied to the bearing.
Engine bearings must work in a fully hydrodynamic oil film regime to survive. Bearing operation in highly loaded race engines is characterized by ultra-thin oil film and frequent direct contact between the bearing and journal surfaces. Without the proper oil clearances and oil viscosity, bearings can fail due to oil starvation and eventual seizure. Bearing material fatigue can also cause bearings to fail. Fatigue results when bearing materials are overloaded. Today’s OE and custom-built racing engines are producing more horsepower than ever before. They require bearing materials that can take more load due to popular turbo-charging and super-charging. Due to the increase in bearing loading, oil film thickness may be insufficient to prevent metal-to-metal contact between the bearing and journal surfaces. One more challenge of highly loaded engines is insufficient rigidity of their crankshafts and housings. Crankshafts bend under load. Their journal surfaces becomes non-parallel to the bearing surfaces. This causes local breaking of hydrodynamic lubrication and edge wear. Bearing overloading can cause the layered materials to crack and separate from their respective steel backs. The separated bearing material particles disrupt the much needed oil film, causing damage to both the bearing and the crankshaft journal surfaces.
The solution to this problem is building stronger bearings for use in these high horsepower racing engines, especially diesel race engines (Diesel Performance applications for Powerstroke, Cummins & Duramax, Sport Compact applications for BMW, Audi & Toyota Supra, to name a few) and high compression ratio alcohol fuel engines (Sprint Car) that produce high pressure in the cylinders.
King bearings has stepped up, and addressed the need for stronger bearings to withstand higher combustion pressures and increased horsepower. One of the stronger materials developed by King is the SV (uncoated) / GPC (coated) series bearings. King’s SV series consists of a unique tri-metal construction that can withstand 30% more load than any other available bearing on the market. SV features a special high strength steel back, a high tin, lead free bronze second layer(that was specially developed for extreme load capacity), and an electroplated silver matrix overlay that serves as an antifriction layer.
The GPC material is created by applying a unique formulated K-340 nano-polymer coating on top of the SV construction with no added thickness. K-340 coating providing excellent antifriction properties (conformability, embedability, and seizure resistance). The K-340 is a strong coating, offering exceptional wear resistance, toughness and fatigue strength. It was created for applying over relatively hard substrates: bronze, aluminum alloys, sputter overlay, and King silver overlay. Hardness of the coating is about 46 HV, which is harder than most aluminum bearing alloys. The coating is able to operate under loads up to 17,400 psi (120 MPa) in diesel direct injection engines, turbocharged gasoline engines and alcohol fuel engines.
Like other King coatings, the GPC coating protects against oil starvation and metal-to-metal contact.
The design and unique materials of King GPC bearings enable them to operate under mixed (partially hydrodynamic) lubrication conditions and extremely high load capacity while providing excellent conformability.
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