Effect of Si Addition on Oxidation Behavior of Nb Containing Ferritic Stainless Steel

Abstract

The effect of Si on the oxidation resistance of high purity Nb containing 19% Cr ferritic stainless steels has been investigated by means of isothermal heating at temperatures up to 1 273 K in air and, the structures of the scale and scale/metal interface were investigated with FE-SEM and FE-TEM. The results are as follows: Si improved the oxidation resistance, as reported in previous studies. The Si addition of about 0.1% improved the limit temperature of the oxidation resistance more than 100 K. The presence of an amorphous SiO 2 layer was found in the interface between the Cr 2 O 3 scale and the metal. This layer might act as an oxidation resistance barrier. In the Si-free steel, a NbO 2 layer formed under the Cr 2 O 3 scale, and the Fe 2 Nb-free region formed beneath the surface. On the other hand, when Si was added, the formation of NbO 2 layer was suppressed. In case of 1%Si, no NbO 2 layer formed and the Fe 2 Nb-free region was eliminated. In addition, Fe particles were present in the Cr 2 O 3 scale in the Si-added steel.

Effect of Titanium on Oxidation Behavior of High-Purity Ferritic Stainless Steel

“…Also, it was suggested that grain-refining owing to Ti addition was due to the presence of Ti at Cr 2 O 3 grain boundaries interrupting the transportation of Cr 2 O 3 grain boundaries in lateral direction. The same mechanism was reported in one of our previously published papers 9) for Mn addition. The thickening of the Cr 2 O 3 scale by the addition of Ti was attributed to the following mechanism.…”

“…9(II), the internal oxidation phase consisted of ª-Al 2 O 3 . In our previously published papers, 9,10) we mentioned that when Nb-containing ferritic stainless steels which also contained small amounts of Al were oxidized in air, the internal Al-containing oxidized phase consisted of ª-Al 2 O 3 , not ¡-Al 2 O 3 . Those results were in agreement with the findings of this study where we used Nb-free steels.…”

Microstructure and properties of WC-11.5%Fe-4%NbH-0.5%C cemented carbides produced by spark plasma sintering

“…This should not be surprising, since niobium is an excellent oxygen getter [15]. However, the amount of niobium oxide is too small to be detected by XRD and its formation may have been caused by a small amount of gas trapped among mixed starting powders and into the powder compact in the die/punch set-up when the temperature reached values above 600 ºC during sintering [27]. The highest and lowest densities for all of the disc samples was obtained for P1250 and R1150, respectively.…”

Cyclic Oxidation Resistance of MoSi2 Added FeCrAlTiY Coatings on ST41 Steel at 700oC Prepared by a Flame Spraying Technique

“…Several studies have reported the beneficial effect of some elements as Si and Mo, in improving the properties of metals and alloys. Inoue et al (2018) reported that an adequate amount of Si addition to stainless steel could promote the formation of SiO2 layer at the substrate/oxide interface. The formed SiO2 can also act as the nucleation site for the formation of Cr2O3 scales (Nikrooz et al, 2012).…”