Downsized turbocharged heavy duty diesel engines with high levels of after treatment such as particulate filter systems and selective catalytic reduction can run hotter with temperatures at the valves and turbocharger exceeding 750°C. Peak cylinder pressures are often pushed up from around 180 bar to 230 bar and beyond. This can lead to challenges in the tribology of the materials used and also in geometric issues from increased distortion around the cylinder head in combination with valve brake systems introducing side loads onto the valve stems, or higher turbo temperatures affecting press fits through differential expansion.
To overcome these challenges, Federal-Mogul has used its well proven Powder Metallurgy technology to add the FM-G15 family to its range of advanced valve guide materials, and two new PM materials, FM-T90A and FM-T82A for turbocharger bushings.
According to Federal Mogul, the FM-G15 family has been designed to meet the requirements of heavy-duty, highly complex engine designs used today. For example, FM-G15A is an alloy developed for high temperature wear resistance and reduced valve stem scuffing through a combination of solid lubricants within a high carbon steel matrix. The solid lubricant package, combined with vacuum oil impregnation, delays valve stem scuffing in high temperature, heavily side-loaded applications.
Meanwhile, the new turbocharger bushing is made from FM-T90A, a cobalt-based, fully dense sintered alloy designed for extreme applications up to 1050°C in corrosive or oxidizing conditions. Federal-Mogul says it is superior to ferrous alloys in harsh conditions because it offers the advantages of powder metal technology, such as complex composite microstructures, not attainable by melt and cast techniques.
The other new turbocharger bushing material designated FM-T82A is a ferrous-based, fully dense composite material with reduced nickel content to provide a cost-effective solution with high temperature properties in aggressive turbocharger bushing applications. This material comprises a microstructure of austenite, alloy carbides and friction-reducing solid lubricant particles, again for operating temperatures high as 1050°C. It is a derivative of Federal-Mogul’s proven 8100 material, and again offers improved high-temperature strength compared to ferritic alloys, yet maintains oxidation resistance and thermal expansion to match common turbocharger housing materials.