New material for power plants

The efficiency of power plants can be increased by raising the steam temperature in the boiler and turbine from 600^oC (at a pressure of 250 bar) to around 700^oC (350 bar) - but that is a temperature that the materials currently used in power plants cannot withstand permanently.

To resolve that issue, ThyssenKrupp VDM researchers have taken an existing nickel-based steel alloy and significantly enhanced its properties.

The result of their work is Alloy 617B, with an optimised chemical composition (OCC) that offers high strength and ductility at the same time as good weldability. In the power plant of the future it could be used in tubes, valves and connectors, as well as in the form of sheet and plate.

Alloy 617B OCC owes its special properties to three factors. First, it is melted and remelted in a vacuum, preventing the pickup of undesirable substances from the air. Second, it contains a minimal amount of boron, whose content has to be precisely defined and controlled. And finally, its molybdenum and carbon contents have been optimised to enhance weldability while retaining the same strength.