Initial oxidation of ferritic interconnect steel, effect due to a thin ceria coating

• Today there exist many ferritic stainless steel grades with a chemical composition speciallydesigned to be used as interconnects in solid oxide fuel cell applications in a temperatureinterval of 650-850°C. The steels have good high temperature mechanical properties andcorrosion resistance as well as good electron conductivity in the formed chromium oxidescale.One way to substantially decrease the high temperature degradation of the interconnectsteel i.e. improve properties such as increased surface conductivity and decreasedoxidation and chromium evaporation is to coat the interconnect steel with suitablecoatings. Today it is well known that a thin cobalt coating hinders chromium evaporationand a ceria coating lowers the oxidation rate at high temperature. Thus, by coating theinterconnect steel the properties are improved to an extent that it should be possible to usea cheaper standard steel, e.g. AISI 441, as substrate for the coatings.In this study the ferritic stainless steel alloys Sandvik Sanergy HT and AISI 441 is oxidizedin laboratory air at temperatures at 750°C, 800°C and 850°C. The results show that a welladhered oxide scale of a complex layered structure is formed with significant amounts ofMn, Fe, Cr and Ti in the oxide scale. A Ce coating significantly reduces the growth rate ofthe oxide scale. The lower Cr content in the AISI 441 alloy does not affect the initial hightemperature corrosion properties when coated with Ce. Also, the results demonstrate theusefulness of ToF-SIMS depth profiling for characterisation of the initial stages of oxidationof SOFC materials.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Bearbetnings-, yt- och fogningsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Manufacturing, Surface and Joining Technology (hsv//eng)

Nyckelord

Steel Forming and Surface Engineering

Stålformning och ytteknik

Publikations- och innehållstyp

vet (ämneskategori)

kon (ämneskategori)