Federal-Mogul Corporation is increasingly using a dual-material cylinder liner technology to reduce bore distortion and improve function in the latest generation of lighter, highly-loaded aluminum-block engines.
Compared to alternative liner technologies, the Federal-Mogul Hybrid Liner, with an aluminum-silicon outer coating, reduces bore distortion in a running engine by two-thirds. Maximum second order bore distortion can be as low as 11% of that experienced by corresponding cast-in liners, while the cylindrical distortion under operating loads is up to three times better. As a result, engine oil consumption is reduced by up to 40%, according to Gian Maria Olivetti, Federal-Mogul’s vice president for Technology and Innovation, Powertrain.
Federal-Mogul’s Hybrid Liner also results in up to 30% higher heat transfer rates, reducing the cylinder wall temperature by up to 40 °C (104 °F) compared to alternative designs. Dynamic strength increases as well; in a cyclic pulsing pressure test, the Hybrid Liner showed no failure at pressures of up to 200 bar, whereas a standard liner block design cracked at 100 bar.
Federal-Mogul is helping engine manufacturers to increase the power output and durability of smaller engines, supporting them in a key area of their global CO2 reduction strategies. Cylinder bore distortion is one of the main factors limiting increases in power and torque outputs, particularly in lightweight aluminium cylinder blocks. Our patented Hybrid Liner increases the strength and stiffness of the combined block and liner assembly, allowing significant weight reduction without compromising engine performance and durability.
—Gian Maria Olivetti
Federal-Mogul’s Hybrid Liner integrates the liner into the aluminium block casting more effectively than alternative technologies, both structurally and thermally, the company claims. The Hybrid Liner comprises a conventional cast-iron sleeve with an aluminium coating applied to the exterior through a proprietary process.
The cast iron sleeve provides good tribological properties and is compatible with cost-effective ring packs. The outer surface of the liner is manufactured to provide a surface topography that is conducive to mechanical interlocking with the aluminium engine block material.
The outer liner coating is an AlSi12 alloy with a melting point below that of the aluminium engine block, which provides outstanding intermetallic bonding between the surfaces of the two materials. To meet the cost and robustness requirements of series production, the coating is applied in a process that uses advanced wire arc thermal spray technology to ensure that coverage, thickness and bonding strength are uniform around the complete height and circumference of each liner.
The coating surface roughness is also controlled, to provide undercuts and micro-porosities so that an extremely strong, intermetallic transition zone is formed between the coating and the block casting material.
Federal-Mogul’s Hybrid Liner also allows engine manufacturers to improve packaging by reducing the distance between adjacent cylinders; pressure die-cast engine blocks with Hybrid Liners can have a material wall thickness of just 3mm between the bores. If a water channel is drilled between two cylinders, the Hybrid Liner technology limits the formation of cracks, allowing coolant to penetrate only as far as the liner coating. Conventional liners can allow water to seep down the joint between liner and casting, reaching the crankcase and contaminating the lubricating oil.
—Gian Maria Olivetti
Federal-Mogul’s Hybrid Liner is produced at its Powertrain Energy manufacturing facility in Friedberg, Germany. The technology was a finalist in the 2012 Automotive News PACE Awards. Federal-Mogul did win a PACE award this year for its Two-Dimensional (2D) Ultrasonic Testing for Raised Gallery Diesel Pistons in the Manufacturing Process category, which recognizes innovations involving game-changing manufacturing or business processes that support the automotive supply chain.