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ThyssenKrupp VDM Superalloy Stands up to Heat, Heavy Oil in Marine Diesel Engine Valves

01/04/2010 - ThyssenKrupp VDM optimizes its high-strength superalloy Alloy 80A for use in the valves of large two-stroke marine diesel engines, where high-temperature corrosion resistance is critical.

ThyssenKrupp VDM has optimized its high-strength superalloy Alloy 80A for use in the valves of large two-stroke marine diesel engines. Because materials for these applications must perform under increasingly high operating temperatures, the newly optimized superalloy Alloy 80A offers significantly improved high-temperature corrosion resistance thanks to an increased chromium content, while the strength of the material has been maintained by the use of further alloying elements.
 
Valves used in modern large marine diesel engines are exposed to high mechanical stresses and are at risk from hot gas corrosion. Very high temperatures in the combustion chamber combine with the heavy oil used in large diesel engines to attack the surface of the valve stems, causing heavy corrosion. The material used for the valves therefore has to be particularly corrosion-resistant and long-lasting. ThyssenKrupp VDM is responding to this challenge with its new superalloy, developed in close cooperation with the Finnish engine maker Wärtsilä and the valve manufacturer Märkisches Werk Halver.
 
As an experienced manufacturer of components for large marine diesels, Märkisches Werk Halver offered the infrastructure necessary to validate and implement the new material in the valve stem application. “The performance of the valve stem is closely linked to the quality of the material,” says project worker Rainer Weigelt from Märkisches Werk Halver. “Meeting all the requirements in one material is a major challenge but is the only way to achieve effective, optimized combustion processes with reduced pollutant emissions.”
 
“In ThyssenKrupp VDM we had an outstanding materials producer with great expertise in high-temperature corrosion on our side,” said Dr. Dietmar Schlager, who headed the project for Wärtsilä. The engine manufacturer has wide-ranging knowledge of the requirements placed on materials and engine components, as well as extensive valve test capabilities.
 
In one of the first tests a valve was made from the new material and fitted in the engine of a container ship. “The results of long-term field testing were very promising,” explained Schlager. “Now we’re testing six further valves and we expect these field tests to deliver more information on production readiness.”
 
The new material also has great potential in other areas, particularly in applications needing high-temperature corrosion resistance in connection with aggressive oil. “We see outstanding prospects for the material in the auto area as well,” says Dr. Jutta Klöwer, project manager at ThyssenKrupp VDM, “particularly given the trend towards more powerful engines with higher combustion chamber temperatures.”