XRD investigations on the oxides grown on hot work tool steels in H2O-containing atmospheres
Résumé
Tool steel modified AISI H11 was oxidized at 600degreesC in mixtures of dry air and water vapor (0 to 30.8 vol% H2O). Either ``time-controlled'' tests (90 hours exposure) or ``wcight-controlled'' tests (oxidation up to 1.5 mg.cm(-2)) were performed. Depending on the H2O-amount added to dry air, two d istinct o xidation k inetics a re o bserved. T he e xternal o xide s cale i s iron-rich (Fe,Cr)(2)O-3. Lattice parameters are determined from the Grazing Incidence XRD patterns. ``Time-controlled'' and ``weight-controlled'' tests show no significant variation of the lattice parameters ``a'' and ``c'' with increasing water vapor in the oxidizing media. The Vegard's law applied to the mean values (a) over bar = 5.036 +/- 0.003 Angstrom and (c) over bar= 13.73 +/- 0.05 Angstrom gives an average composition of 4.7 mol% Cr2O3 in (Fe,Cr)(2)O-3. Texture is characterized by performing Rocking Curves. It strongly depends on the oxidation time and is only observed for the higher H2O-contents in the oxidizing media.