Influence of surface preparation on oxidation of stainless steels at high temperature (original) (raw)
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ISIJ International, 1994
The influence of alloy surface preparation as induced by mechanical polishing and electropolishing on the oxidation behaviour of AISI 316 stainless steel in dry air under non-isothermal heating (6 K•min~1) followed by isothermal holding at 1 423 K is reported. Mechanically polished surfaces exhibit a shorter incubation period for initial oxidation but better oxidation resistance during isothermal holding as compared to electropolished surfaces. Such observation is attributed to enhancedoutward diffusion of Cr for easy and early establishment of Cr-rich oxide layer on the mechanically polished surfaces. Themorphologies of the scales and nature of their adherenceto the alloy substrates have beencharacterized by SEM. Distribution of the alloying elements like Ni. Cr, Mn, Mo. Si as well as Fe and oxygen across the oxide layers and the type of compounds formed have been examined by EPMA. EDSand XRD techniques. SEM examinations of the alloy/scale cross section for the mechanically polished and oxidized steel, supplementedby the X-ray imagesof the respective elements, indicate preferential formation of a continuous Cr-rich layer near the oxidelair interface along with two continuous bandsof dopedCr203at the scale/alloy region. Onthe other hand, the scale formed on electropolished surfaces of the steel showsfragmented Ni-rich and Cr-rich oxide areas at the bottom region of the scale with mostly compact Fe303-rich layer at the oxide/air interface.
The oxidation behavior of grade 304L stainless steel (SS) subjected to different surface finishing (machining and grinding) operations was followed in situ by contact electric resistance (CER) and electrochemical impedance spectroscopy (EIS) measurements using controlled distance electrochemistry (CDE) technique in high purity water (conductivity < 0.1 S cm −1 ) at 300 • C and 10 MPa in an autoclave connected to a recirculation loop system. The results highlight the distinct differences in the oxidation behavior of surface worked material as compared to solution annealed material in terms of specific resistivity and low frequency Warburg impedance. The resultant oxide layer was characterized for (a) elemental analyses by glow discharge optical emission spectroscopy (GDOES) and (b) morphology by scanning electron microscopy (SEM). Oxide layers with higher specific resistivity and chromium content were formed in case of machined and ground conditions. Presence of an additional ionic transport process has also been identified for the ground condition at the metal/oxide interface. These differences in electrochemical properties and distinct morphological features of the oxide layer as a result of surface working were attributed to the prevalence of heavily fragmented grain structure and presence of martensite.
Le Journal de Physique IV, 1993
Stainless steels of type AISI 304 and 316 were heated in air (1-5-15 minutes at 900-1000-1 100 OC) and the oxide layers formed on the surface were analyzed by XRD, CEMS, SIMS and FTIR. At these temperatures the main oxides are CrgOs and a spinel close to MnCr204 for polishing samples (with Fez03 for the chemically cleaned samples). The oxidation induces a Cr and Mn depletion from the metallic substratum and a phase transformation y (f.c.c.) + cu (b.c.c.) in a thin layer of the stee!s near the oxidesmetal interface.
Effect of surface finishing on the oxidation behaviour of a ferritic stainless steel
Applied Surface Science, 2017
The corrosion behaviour and the oxidation mechanism of a ferritic stainless steel, K41X (AISI 441), were evaluated at 800 • C in water vapour hydrogen enriched atmosphere. Mirror polished samples were compared to as-rolled K41X material. Two different oxidation behaviours were observed depending on the surface finishing: a protective double (Cr,Mn) 3 O 4 /Cr 2 O 3 scale formed on the polished samples whereas external Fe 3 O 4 and (Cr,Fe) 2 O 3 oxides grew on the raw steel. Moreover, isotopic marker experiments combined with SIMS analyses revealed different growth mechanisms. The influence of surface finishing on the corrosion products and growth mechanisms was apprehended by means of X-ray photoelectron spectroscopy (XPS) and residual stress analyses using XRD at the sample surfaces before ageing.
High-temperature oxidation behaviour of nanostructure surface layered austenitic stainless steel
Langmuir, 2022
The present study investigates the high-temperature oxidation behaviour of nanostructure surface layered AISI 304L stainless steel. A severely deformed layer of ~300 μm thickness, consisting of nanoscale grains (~40 nm size) in the topmost region, is successfully developed using the surface mechanical attrition treatment (SMAT) process. The SMATed layer is substantially stable up to 700 • C; however, the surface hardness is reduced by ~37% at 800 • C for 25 h oxidation duration. Glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy analysis revealed the considerable difference in the chemistry and elemental distribution across the oxide scale of SMATed and non-SMATed specimens. Adherent, denser, and thinner scale, dominated by nanocrystals of Cr-and Mn-rich oxides, is formed on the SMATed steel. However, the Fe-oxide dominated scale containing micro-crystals is found on the non-SMATed specimens, which shows noticeable exfoliation. A high density of grain boundaries and lattice defects in the SMATed layer display admirable reactive diffusion properties of Cr and Mn during oxidation of steel, instigating the formation of a protective oxide scale. The SMATed specimens exhibit multiple zones in the oxide scale: (i) Cr/Mn depleted outer layer, (ii) Cr-/Mn-rich inner layer, and (iii) gradually decreasing Cr/Mn region.
On the Structure of Initial Oxide Films on Stainless Steel in High Temperature Water and Vapor
Transactions of the Japan Institute of Metals, 1970
The present authors have studied the structures and chemical compositions of oxide films produced on surfaces of 18-8 and vapor on the structures and chemical compositions of the oxides were investigated through electron microscopy, transmission electron diffraction and X-ray microanalysis. Main results obtained are as follows: (1) A corundum type oxide produced on a mechanically polished surface of 18-8 stainless steel at the early stage of oxidatype oxide has been changed to a spinel type oxide containing Ni after a prolonged heating time (24hr). (2) After heating in high temperature vapor (dryness: 0.18) of 18-8 stainless steel, the corundum and spinel type oxides are found on both mechanically and chemically (or electrolytically) polished surfaces. In the case of the higher dryness (1.0), however, the corundum type oxides are detected on the three differently polished surfaces. (3) On heating 18Cr stainless steel in high temperature water and vapor under the same conditions, the oxide films are of the corundum type containing Fe and Cr. This evidence throws a light on the contribution of Ni to the formation of the spinel type oxides detected in the initial oxide films of 18-8 stainless steel.
Thin Solid Films, 2002
The influence of implanted Si, Mo and Ce vs. the as-received austenitic AISI 304 stainless steel has been studied after isothermal oxidation in air at 900 8C for 32 h. The oxide layer formed was characterised by means of conventional X-ray diffraction, scanning electron microscopyyenergy-dispersion spectroscopy and X-ray absorption spectroscopy (XAS) techniques. The projected ranges of the implantation were calculated using the TRIM code. The results obtained by the most sensitive technique, XAS, show slight differences in the chemical composition of the oxide layer of the different ion-implanted samples. However, these chemical differences could determine a threshold between acceptable and non-acceptable oxidation behaviour. The evolution of the chemical composition from the oxide-metal interface to the oxide surface has also been studied. XAS spectra show that Cu diffusion is favoured in the oxide layer for the non-implanted sample, which does not occur for implanted samples. Both Si and Ce ion implantation promotes active diffusion of Cr and Mn from the parent steel to form a protective oxide layer, whereas Mo implantation induces major participation of Fe in the oxide scale. This may have been caused because of volatilisation of molybdenum oxides. ᮊ
Stainless steels of type SUS304 and SUS316 were chemically treated and heated at various temperatures, and the oxide films formed on the surface were analysed by Auger electron spectrometry and conversion electron M6ssbauer spectrometry. The outermost oxide layers of stainless steels were enriched with iron and chromium after heat treatment below 600 ~ C and above 700 ~ respectively. It was found that at least two magnetic components of iron species were present in the oxide layers of stainless steel heated below 600 ~ C and that the fine particles of iron oxide are produced in the inner oxide layers of the samples prepared by heating at temperatures higher than 700 ~ C. Only paramagnetic iron species were detected in the oxide layers of the stainless steel prepared by chemical treatment. The structures of the oxide layers produced by those heat and chemical treatments are proposed.
Effects of the stability of austenitic phases worked by shot-peening on the structures and chemical compositions of oxide films formed on 18-8 and 18-18 stainless steels by wet oxidation have been studied mainly by electron diffraction and characteristic X-ray micro-analysis. The following results are obtained by the present investigation. The oxide films formed on the surfaces of 18-8 stainless steels worked by shot-peening after mechanical or chemical On the contrary, the surface of the 18-18 stainless steel worked by shot-peening was covered with an oxide film which gave diffraction patterns showing clearly the existence of spinel type oxides with corundum type oxides of weak intensity under the same oxidizing conditions as in the case of 18-8 stainless steel. Further, besides Fe and Cr, Ni was detected from this oxide film. And the residual strain introduced by the shot-peening did not affect the structures and compositions of the wet oxidized films. From the above, it becomes clear that the stability of austenitic phases affects the structures of oxide films formed by wet oxidation of Fe-Cr-Ni austenitic stainless steels.
Pre-oxidation of stainless steel: a study by diffuse reflection spectroscopy
Applied Surface Science, 1998
Stainless steel pre-oxidation by H O was studied by diffuse reflection spectroscopy as a function of exposure time, 2 2 temperature, concentration of H O and pH of the reagent solutions. Full quantification of the diffuse reflection 2 2 spectroscopy is carried out by combining absorption, reflection and interferometric features yielded by the passive layer. The oxide layer, which consists mostly of a hematite solid solution is characterised by spectral analysis. Its thickness is derived from the diffused reflection spectral data and analysed as a function of the investigated experimental parameters.