Material for high temperature application in liquid metals

Liquid metals like Pb, PbBi, Sn and Na are promising heat transfer fluids (HTF), e.g. for concentrating solar power (CSP), thermal energy storage (TES) and CO2-free thermal decomposition of methane. In addition, liquid metals are envisaged as cooling fluid in advanced nuclear reactors and as working media in spallation particle sources.
The selected metals are characterised by high thermal conductivity and comparatively low viscosity, by good chemical stability in a wide range and low vapour pressure. The
major drawback is the poor compatibility of most metallic materials with the liquid metals, the liquid metal corrosion (LMC). LMC includes 3 main corrosion mechanisms:
(1) dissolution of constituents of the solid material into the liquid metal (2) dissolution and penetration of the liquid metal into the structural material, and (3) formation of
intermetallic compounds and solid solutions. The common counter measure against LMC in liquid Pb alloys is the solution of oxygen in the liquid metal to allow in-situ
formation of protective oxide scales on steel surfaces without Pb oxide precipitation. Austenitic (e.g. AISI 316L) and ferritic-martensitic (F/M) steels (e.g. ... mehrT91) are able to
form protective iron-based oxide scales in Pb alloys with an oxygen content between 10-8 and 10-6wt% up to 500°C. At higher temperatures, the protection provided by iron oxides fails. Alloying steels or the surface of steels with strong oxide-forming elements such as Si and Al can increase the operating temperature and enlarge the allowable oxygen range. Another possibility is the use of protection layers that are insoluble in Pb alloys. In low-oxygen or oxygen free environment e.g. in Na, Li or Sn (for methane decomposition) oxide scale formation as protection method does not work. In such a case, structure materials or elements that can withstand these corrosive environments have to be found. At the IHM, corrosion tests in stagnant liquid metals, tests in turbulently flowing conditions, fretting wear tests, and material development are the main objectives. Dedicated test facilities were built and are available at the institute. The poster gives an overview on our expertise and work and presents the latest results.