Valve materials for heavy-duty engines at IAA Commercial Vehicles

The materials, which will be on display at the forthcoming IAA Commercial Vehicle show in Hanover, Germany, are the result of a ‘twin-track’ approach by the company to define both an upgrade to conventional austenitic steel and also a more cost-effective alternative to high nickel ‘super alloys’.

As in the light vehicle market, the quest for improved fuel economy is driving the trend of downsizing and boosting in heavy-duty diesel engines. Previous generations of 16l engines have been replaced by 12 and 13l units, with even 10 or 11l engines now producing 500hp.

This has led to a requirement for valves with increased high temperature strength that can withstand combustion pressures of 220bar and above, while at the same time emissions reduction strategies are increasing the levels of Exhaust Gas Recirculation (EGR) exposing the valves to greater risk of wet corrosion.

“For demanding applications the conventional answer is a premium material such as Federal-Mogul Powertrain’s ECMS-Ni80A, but with a Nickel content greater than 70% this is not always an economic solution,” explained Gian Maria Olivetti, Chief Technology Officer, Federal-Mogul Powertrain. “We have established new ways to make more effective use of the expensive alloying elements such as Nickel by validating materials with equivalent hot strength to ECMS-Ni80A, but lower alloy content.”

The main factors that differentiate the new materials in the range are the percentages of Nickel (Ni), Chrome (Cr) and Manganese (Mn) that they contain. One of the upgraded alloys, ECMS-2512NbN, is a development from standard CrMn austenitic steel designed to suit both inlet and exhaust applications experiencing elevated temperatures. By increasing the Nickel content from the usual three to around 12% while fine-tuning the combination of other elements in the alloy, both hot strength and corrosion resistance are significantly enhanced.

For higher temperature applications, ECMS-Ni36 high performance austenitic steel alloy has a superior resistance to hot oxidation than its industry standard equivalent, ECMS-3015D(austenitic steel with 15% Chromium and 31% Nickel). Additionally, despite having only 36% Nickel content, it has similar tensile strength to the superalloy ECMS-Ni80A, which contains more than 70% Nickel.

The development and validation process for a new valve material, which can take up to 10 years, includes the identification of appropriate alloying elements and limits on composition as well as the subsequent effect on grain structure. Exhaustive internal validation by Federal-Mogul to prove suitability for future market challenges then follows.

Guido Bayard, Director, Global Valvetrain Technology, Federal-Mogul Powertrain commented: “The very high level of alloying elements present makes these materials quite special. In order to predict reliability and conformity to engine applications, a wide range of rig and laboratory tests on wear, corrosion and durability are conducted, with a series of engine application trials on dynamometers also completed.”

Federal-Mogul is already in series production with valves made from ECMS-2512NbN and ECMS-3015D, while ECMS-Ni36 valves are undergoing trials with customers ahead of further production launches.

The alloys ECMS-2512NbN and ECMS-Ni36 are equally applicable to on-highway, off-highway and leisure marine applications in the 10-16 litre category; for heavy-duty applications where the requirements exceed even the capabilities of ECMS-Ni80A valves, for example some marine and CNG high output engines, Federal-Mogul provides valves with hollow stems that have enhanced heat dissipation performance.

To ensure the maximum efficiency and durability of its valves in service, Federal-Mogul also manufactures a wide range of associated components including retainers, cotters and valve rotators. These will be on show together with a selection of valves on Federal-Mogul Powertrain’s stand at IAA Commercial Vehicles, Hanover from 21^st-29^th September 2016. The company will exhibit at Booth C28 in Hall 13.