Kinetics Oxidation and Characterization of Cyclically Oxidized Layers at High Temperatures for FeMnSiCrNiCe and FeSiCrNi Alloys

Abstract

Conventional stainless steels are used in cyclic oxidation, but the high amount of Cr and mainly Ni increase the price of these alloys. The objective of the present study was to assess the cyclic oxidation resistance of FeSiCrNi and FeMnSiCrNiCe alloys in comparison to AISI 304 and AISI 310 stainless steels by evaluating the oxidation kinetics and using characterization techniques to determine the oxides formed. The alloys were melted in induction furnaces and cast in sand molds. Cyclic oxidation tests were carried out in an automated oven in cycles of one hour for heating and maintenance at high temperature (850, 950 or 1050 ºC) and 10 minutes for cooling. To characterize the oxidized layers, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) analysis were performed. The oxidation kinetics were determined. The results showed that the studied alloys presented better results than AISI 304 at 850 ºC, but at 1050 ºC, AISI 310 presented the best results. At 950 ºC, the FeSiCrNi alloy presented layer detachment and FeMnSiCrNiCe presented a higher rate of mass variation than AISI 310, both without oxide detachment. For both alloys, formation of chromium and manganese oxides with parabolic rate of mass gain occurred.

High temperature cyclic oxidation behavior of a low manganese Fe12Mn9Cr5Si4Ni-NbC shape memory stainless steels

“…Furthermore, the oxides predicted by Thermo-Calc here, as also already reported for three Fe-Mn-Si-Cr-Ni alloys [5,6] are in accordance with the increase of MnCr 2 O 4 phase as p(O 2 ) decreases (Figure 4). Regarding the other phases predicted by Thermo-Calc simulation (Olivine, Rhodonite, Halite and so on) none of them were found here or reported during previous characterization of Fe-Mn-Si-Cr-Ni alloys oxidized [4][5][6][7][8]13]. Silica oxide was also never observed in these alloys after oxidation at 800 °C, although it was reported after oxidation at 600 °C [9].…”

“…The horizontal cracks were reported to be the cause of oxide delamination in an Fe-17Mn-Si-Cr-Ni-VC alloy, generating oxide spallation [13]. In the present case, no mass loss occurred, probably due to the mechanical anchoring [13] from the metal/oxide roughness, which was observed after cyclic and isothermal oxidation for these alloys [5,7,13]. The layer formed 11 between the oxide scale and the metallic substrate as already mentioned was reported to be a ferrite layer in similar alloys, formed due the Mn depletion during the alloy oxidation [5,7,11,13], in good agreement with XRD results presented in Figure 2.…”

“…These authors found Mn 2 O 3 , in the external layer basically, Mn 3 O 4 at middle layer and MnCr 2 O 4 located at the metal/oxide interface. Furthermore, it was reported that a Mn-depleted zone was formed below the oxide layer [4][5][6][7]11,13], where a metallic transformation from austenite to ferrite occurs. This fact explains the Fe-α peaks observed by XRD.…”

“…They observed that during oxidation at high temperature the oxide layer presents Mn-rich oxides (Mn 2 O 3 and Mn 3 O 4 ) and Mn-Cr-spinel, causing depletion of Mn and generating a ferrite layer near the metal/oxide interface. After that, several studies were developed in order to try improving the oxidation resistance of these alloys, named as shape memory stainless steels (SMSS) [4,[6][7][8].…”

“…However, the Fe-8.26Mn-5.25Si-12.80Cr-5.81Ni-11.84Co alloy is more expensive and present a generalized precipitation of intermetallic phases due to exposure to high temperature. Addition of Ce [7] was also used as a way to improve oxidation resistance during cyclic tests at 850, 950 and 1050 °C, in an Fe-13.58Mn-5.58Si-9.42Cr-3.86Ni-0.18Ce, but the mass gain was similar to that of conventional SMSSs. Indeed, the mechanism related to Ce alloying has not been deeply investigated yet.…”