SECONDARY-ION MASS-SPECTROMETRY AND MULTIREFLECTION INFRARED ANALYSESOF CONVERSION COATINGS ON FE-CR-AL STAINLESS-STEELS FOR CATALYSIS - STUDY OF THERMAL-STABILITY
L. Aries et J. Roy, SECONDARY-ION MASS-SPECTROMETRY AND MULTIREFLECTION INFRARED ANALYSESOF CONVERSION COATINGS ON FE-CR-AL STAINLESS-STEELS FOR CATALYSIS - STUDY OF THERMAL-STABILITY, Materials science and technology, 10(5), 1994, pp. 359-363
The thermal stability of three stainless steel conversion coatings for
high temperature applications (e.g. photothermal conversion catalysis
) are investigated. The thermal oxidation in air up to 1000-degrees-C
of Fe-17Cr, Fe-18Cr-1.3Al, and Fe-22Cr-5 Al coatings (all wt-%) are co
mpared. This study has revealed a critical temperature below which the
coating thickness is preserved; the critical temperature increases an
d the thermal oxidation of the conversion coating decreases with highe
r chromium and aluminium content. This is attributed to the difference
in the substitution ratio of gamma lacunar phase (additionally oxidis
ed substituted magnetite), which is the main component of the conversi
on coatings. The thermal stability of this phase is higher when it is
richer in chromium or aluminium. Higher contents of these elements rai
se the temperature of formation of chromite (FeCr2O4) and alumina, the
occurrence of which causes thickening of the coating during thermal t
reatment.