High temperature oxidation behavior of AISI 304L stainless steel—Effect of surface working operations (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.
Materials Characterization, 2012
The effect of surface working operations on the microstructure, electrochemical behavior and stress corrosion cracking resistance of 304L stainless steel (SS) was investigated in this study. The material was subjected to (a) solution annealing (b) machining and (c) grinding operations. Microstructural characterization was done using stereo microscopy and electron back scattered diffraction (EBSD) technique. The electrochemical nature of the surfaces in machined, ground and solution annealed condition were studied using potentiodynamic polarization and scanning electrochemical microscopy (SECM) in borate buffer solution. The stress corrosion cracking resistance of 304L SS in different conditions was studied by exposing the samples to boiling MgCl 2 environment. Results revealed that the heavy plastic deformation and residual stresses present near the surface due to machining and grinding operations make 304L SS electrochemically more active and susceptible to stress corrosion cracking. Ground sample showed highest magnitude of current density in the passive potential range followed by machined and solution annealed 304L SS. Micro-electrochemical studies established that surface working promotes localized corrosion along the surface asperities which could lead to crack initiation.
Influence of surface preparation on oxidation of stainless steels at high temperature
Surface and Interface Analysis, 1993
Fourier transform infrared specular reflectance spectra at variable incidence have been recorded in order to characterize the oxide layers formed on both mechanically polished and etched surfaces of stainless steels (AISI 304 and 316). Depending on the surface preparation, the major oxides are either Cr2O3 and MnCr2O4 for polished samples or α-Fe2O3 and Fe3O4 for etched samples in the early stages of the oxidation in air at 900°C. Secondary ion mass spectrometry depth profiles confirm the schematic structure of oxide films (developed on polished surfaces during longer exposures) deduced from infrared reflectance study.
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.
Surface Modification of 304 Stainless Steel by Electro-Spark Deposition
Journal of Materials Engineering and Performance, 2018
Electrospark Deposition (ESD) is a pulsed micro-welding process that is used to apply surface coatings for repair of damaged high value precision products or modify their surfaces for specific properties. The low heat input, small heat affected zone and the ability to form metallurgical bonding of coating to substrate are some of the major advantages of ESD process. Many applications require the components to have excellent surface performance, such as wear resistance and corrosion resistance. To meet these requirements, some components are built with specific materials, compromising other properties and cost. ESD technique provides an approach to modify the component surface without compromising the bulk properties. Stainless steel is an ideal material for many applications such as industrial equipment, surgical instruments, household hardware etc., due to its resistance to corrosion. Surface modification of stainless steel may improve its performance and may open new applications. In this study, surface modification of 304 stainless steel by ESD was investigated. TiC, WC and Molybdenum (Mo) were employed as coating materials. The ESD processing windows for these coatings were investigated. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis was conducted to characterize the microstructure and composition of coated stainless steel. Micro-hardness and wear resistance tests were carried out to evaluate the mechanical properties of coated stainless steel. TiC and WC coatings dramatically increase the micro-hardness of 304 stainless steel. WC coating improves the abrasion wear resistance of stainless steel by more than 5 times, while TiC and Mo coatings also improve it by 2.5 times. Electrochemical tests were conducted to investigate the corrosion resistance of coated stainless steel. Mo coating exhibits significant improvement on corrosion resistance in 5% NaCl solutions, iv which corrodes 350 times slower than stainless steel. TiC coating also increases the corrosion resistance with 10 times slower corrosion rate. WC coating does not show improvement on the corrosion resistance. Electrochemical impedance spectroscopy (EIS) was employed to further investigate the electrochemical behavior of coated stainless steel. The results showed the polarization resistance of Mo coated sample is much larger than that of base metal stainless steel. XRD analysis indicate the phase transformation from austenite to ferrite after ESD of Mo. Comprehensive metallurgical analysis of Mo coated 304 stainless steel is performed after heat treatment at 400ºC, 650ºC and 900ºC. The effects of heat treatment atmosphere are investigated by comparing the sample treated in air and Ar gas. SEM and EDX results show the coating thickness decreases with the increase of heat treatment temperature. Localized Mo rich area is found in heat-treated samples. More cracks, porosities and rougher surface conditions are observed in heat-treated samples. XRD analysis display phase transformation from austenite to ferrite at 400ºC. Mo rich intermetallic is detected at 650ºC under Ar gas. Mo and Cr oxides are found in heat-treated samples above 650ºC in air. XPS results show metallic state Mo disappears after heat treatment in air, while metallic state Mo only disappears at 650ºC in Ar gas. It is suggested that Mo rich intermetallic is formed at specific temperature range around 650ºC. Electrochemical test indicated heat-treated samples, either in Ar or in air atmosphere, have lower corrosion resistance than as-deposited sample. Metallic state Mo and a certain ratio of austenite and ferrite can contribute to better corrosion resistance. EIS analysis with modified equivalent circuit is conducted to further investigate the electrochemical behavior. The results indicate that heat-treated samples introduce more nonuniform coating layers because of oxidation and diffusion of alloy elements. Mo rich intermetallic phase decreases the corrosion potential of the heat-treated sample at 650ºC in Ar, and also decreases the corrosion rate of the sample. v I would like to thank Mr. Nigel Scotchmer, Kevin Chan and Dominic Leung at Huys Industries Ltd. for their assistance and technical support. I would like to thank Huys industries Ltd, Ontario Centres of Excellence (OCE) and National Sciences and Engineering Research Council (NSERC) for providing financial support for this work. I also thank TechnoCoat Co.,Ltd, for materials support. The advice, encouragement and counsel of Dr. Joyce Koo during times of need are the reasons I am capable of finishing this project. I'd like to express my gratitude for her help of getting materials, sharing references and invaluable discussions.
Surface and Interface Analysis, 2008
Surface oxidation of Fe-19Cr-17Ni, Fe-19Cr-18Ni-1Al and TiC-enriched Fe-19Cr-18Ni-1Al alloys was investigated by photoelectron spectroscopy (PES). The experiments were conducted at 323 K in pure O 2 (2.7 × 10 −6 mbar). Composition and morphology of the nanoscale surface oxides were determined quantitatively by inelastic electron background analysis. Moreover, use of synchrotron radiation facilities were necessary to obtain improved sensitivity for studying minor alloying elements such as Al and Si. The results indicate oxygen-induced segregation of Al, which significantly hinders the oxidation of the major alloying elements Fe and Cr. Ti remains in its inert carbide form. The relative concentration of Fe within the oxide layer was found to increase with the oxide-layer thickness, indicating greater mobility of Fe relative to other alloying elements.
Electrochemical Behaviour of Surface Modified AISI 304 Grade Stainless Steel in Ringer’s Solution
Transactions of the Indian Institute of Metals, 2011
Stainless steels are widely used as orthopedic implant materials. The main problems with these implant materials are fatigue fracture, fretting fatigue, wear and corrosion. Surface mechanical attrition treatment (SMAT) is a newly developed method to improve the materials properties and performance. In the present study, AISI 304 SS was subjected to SMAT using 2, 5 and 8 mm [ 316L SS balls for 15, 30, 45 and 60 min at 50 Hz under vacuum. SMAT of 304 SS increased the surface roughness, induced the formation of mechanical twins, strain induced martensite phase, and increased the defect density, which is a function of the size of the balls and treatment time. SMAT using 5 and 8 mm [ balls significantly decreased the corrosion resistance whereas treatment using 2 mm [ balls enabled an anodic shift in E corr and a marginal decrease in i corr . However, increase in surface roughness leads to the formation of a defective passive film and a decrease in breakdown potential.
ELECTROCHEMICAL MEASUREMENTS OF ANODIZING STAINLESS STEEL TYPE AISI 304
Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with its environment. Stainless steels have surface passive layer which exhibits a truly remarkable property: when damaged (e.g. abraded), it self-repairs as chromium in the steel reacts rapidly with oxygen and moisture in the environment to reform the oxide layer. If the oxide forms a continuous layer on the surface it will stop or slow down the oxidation process and protect the metal from further corrosion. The oxide layer is enhanced with further thickening by anodizing process . This work deals with comparative study of corrosion behavior of mechanical polishing, electropolishing and anodizing 304 stainless steel specimens. Electrochemical measurements are applied using open circuit, polarization and cyclic polarization at room temperature in sea water (3.5% NaCl, pH 6.7). Improvement in corrosion resistance is clearly observed for specimens after anodizing process that shown, Ecorr= -359.6 mV and icorr=3.83μA/cm2, while the specimen after electropolishing, Ecorr=- 398.8mV and icorr=4.69μA/cm2, and specimen before treated, Ecorr=-419.9 mV and icorr=5.56μA/cm2, and pitting potential increases in positive direction.
CORROSION SCIENCE AND …, 2009
In this study the effect of different surface finishing techniques on the pitting corrosion behaviour of a commercial 304 stainless steel alloy was investigated. Surface finishing methods were divided into two categories, i.e. mechanical and chemical. Mechanical treatment methods include power tooling such as grinding, emery paper brushing, stainless steel wire brushing and stainless steel shot blasting. Chemical treatment methods include chemical passivation (phosphoric acid, citric acid, nitric acid) and electro-cleaning (phosphoric acid and citric acid). Potentiodynamic polarization experiments were carried out in 3.5 wt. % NaCl solution at room temp. (20 ℃). The results showed that chemical treatment methods improved the corrosion resistance of stainless steel 304, measured in terms of pitting potential (Epit). Corrosion resistance of the specimens was increased in the order of; electro-cleaning > manual passivation > mechanical cleaning. Surface of electro-cleaned specimens was smoother than rest of the surface treatment methods. Chrome content in chemically treated specimens was higher than in mechanically treated specimens as shown by EDX analysis.