Stainless Steel In Air Research Articles

Effects of chromia coatings on the high-temperature behavior of F17Ti stainless steel in air. Effect of rare-earth-element oxides

The MOCVD technique was used to form thin films of chromia and/or of a rare-earth-element oxide on the surface of F17Ti stainless-steel samples. These oxides were deposited alone or together, successively or by codeposition. Coated samples were then subjected to high-temperature oxidation tests, either under isothermal conditions at 1273 K for 50 h, or under cyclic conditions at 1223 K for 40 cycles. An improved oxidation behavior was observed in every case, especially with codeposited Ln2O3-Cr2O3. Weight gain decreased during oxidation, compared with an uncoated sample, and scale spallation, generally observed under cyclic conditions, disappeared. Longer time experiments were also carried out. Large differences were observed, depending on the sample surface treatment.

オーステナイト系ステンレス鋼ＳＵＳ３０４の２８８℃大気中におけるマイナー則の検討

The effect of fluctuating stress on the fatigue strength of type 304 stainless steel in air at 288°C was examined. In any of the 2 step increasing stress, 2 step decreasing stress, repeated 2 step stress (high to low), repeated 2 step stress (low to high) and gradual increasing stress, the cumulative usage factor calculated based on the linear damage law exceeds 1. In the 2 step increasing or decreasing stress, the usage factor for the decreasing stress type is larger than the increasing stress type. On the other hand, the cummulative usage factor for the repeated 2 step stress (low to high) is larger than the repeated 2 step stress (high to law), and the usage factor increases with increasing number of cycles at the first stress. The smaller the difference between the first stress and the second stress, the larger the usage factor. In the gradual increasing stress, the usage factor increases with increasing number of cycles at each stress.

Effect of chromia and alumina coatings on the high-temperature behaviour of F17Ti stainless steel in air: effect of a rare earth element oxide

The MOCVD technique was used to deposit thin oxide films of chromium, aluminium and rare earth elements on stainless steel surfaces. These oxides were deposited alone or together, successively or by codeposition. Coated samples were then submitted to high-temperature oxidation tests, under isothermal conditions at 1273 K, or under cyclic conditions. An improvement in steel behaviour was observed in every case, particularly for codeposited Ln 2O 3/Cr 2O 3: the weight gain decreased during oxidation, and the scale spallation phenomenon disappeared under cyclic conditions, enhancing the alloy lifetime.

オーステナイト系ステンレス鋼の高サイクル疲労強度に関する研究（第１報） オーステナイト系ステンレス鋼ＳＵＳ３０４の高温大気中および高温純水中の疲労強度に及ぼす表面処理の影響

Effect of preliminary surface working on the fatigue strength of type 304 stainless steel in air and pure water both at 288°C was examined. The surface finishings were electropolishing, emery paper polishing, shot peening, shot peening followed by emery paper polishing, and glassbead peening. While the residual stress introduced by shot peening was very highly compressive, the fatigue strength was not so much increased. However, the fatigue strength of the shot peened and then emery paper polished stainless steel was remarkably increased. The fatigue strength of the glassbead steel in air was much more improved compared with the shot peened stainless steel. The fatigue strength of the glassbead peened steel was also increased in high temperature water, but the degree of improvement was not so high compared with that in air.

MICROSTRUCTURAL AND ENVIRONMENTAL EFFECTS ON FATIGUE CRACK PROPAGATION IN DUPLEX STAINLESS STEELS

Abstract— Fatigue crack initiation and propagation in duplex stainless steels are strongly affected by microstructure in both inert and aggressive environments. Fatigue crack growth rates in wrought Zeron 100 duplex stainless steel in air were found to vary with orientation depending on the frequency of crack tip retardation at ferrite/austenite grain boundaries. Fatigue crack propagation rates in 3.5% NaCl solution and high purity water are increased by hydrogen assisted transgranular cyclic cleavage of the ferrite. The corrosion fatigue results are interpreted using a model for the cyclic cleavage mechanism.

The influence of crack closure on the positive load ratio ( [formula omitted]) dependence of fatigue threshold stress intensity factor range ( [formula omitted]) of AISI 316 stainless steel in air at room temperature

Near-threshold fatigue crack growth (FCG) behaviour of 316 SS at positive R- ratios in air at room temperature is influenced by crack closure. Empirical modifications of McEvily-Groeger and Zhao Xiaopeng equations are proposed to incorporate crack closure effects; the modified equations are found to provide excellent correlation for the R- dependence of the present ΔK th data.

Relationship between Fatigue Crack Propagation Properties and Film Thickness.

The relationship between fatigue crack propagation properties and thickness of films such as oxide film and passive film was analyzed. The data of fatigue crack propagation properties employed were obtained for carbon, low-alloy, high-strength and stainless steels in air at test temperatures between -25 and 550°C and in 3%NaCl aqueous solution, avoiding crack closure. When the relationship of fatigue crack propagation rate, da/dN, to effective stress intensity factor range, ΔKeff, was expressed by da/dN=C*{(ΔKeff/E)m-(ΔKeff, th/E)m}=C*(ΔKeff/E)m-(da/dN)*…(A) where C* and m were constants, E was Young's modulus and ΔKeff, th was the threshold, the following three equations were obtained : C*=1.3×105ζ0.5…(B) (da/dN)*=ζ…(C) ΔKeff, th/E=6.7×10-4η0.25…(D) Here, ζ was the thickness of films formed at the crack tip for each loading cycling, which was estimated from oxidation behavior on the alumina-polished surface in air at elevated temperatures and from corrosion behavior on the bare surface in 3%NaCl aqueous solution. The films were the oxide film in air at elevated temperature and the water-adsorbed and passivated films in 3%NaCl aqueous solution. η was the film thickness measured on the fracture surface at the threshold level. Substituting Eqs. (B) and (C) into Eq. (A), and Eqs. (B) and (D) into Eq. (A), two predictions of fatigue crack propagation were obtained. Both predictions were in good agreement with the experimental data.

ラマン分光法によるステンレス鋼の高温酸化皮膜の評価

Raman spectroscopy should be a useful technique for a nondestructive characterization of surface layers on metals. In this study, Raman spectroscopy has been used to examine oxide layers formed on stainless steels in air at elevated temperatures.Specimens of commercial austenitic stainless steels (SUS304, SUS316 and SUS310S) were prepared by polishing with #1200 emery paper and degreasing in an ultrasonic bath of acetone. Oxidations were carried out in a preheated furnace at 573-1073 K for 1.8-3600 ks. Raman spectra were obtained from these oxide layers formed on stainless steels. Auger depth analysis was also used to study the oxide layers.When oxidation temperature was below about 873 K, it was clarified that iron oxides such as Fe2O3 and Fe3O4 were formed. On the other hand, the surface oxide layers at above 873 K were composed of Cr2O3, MnCr2O4 and FeCr2O4. The composition of stainless steels was less dependent on these oxidation behavior. The thickness of the oxide layer formed at 1073 K for 7.2 ks was estimated at about 400 nm by Auger depth profiling. From a comparison of the Raman spectra with Auger depth profiling, it was concluded that the Raman spectra measured in this study were obtained from the whole layer of the surface oxide film. Therefore, Raman spectroscopy technique can be applied to the characterization of the oxide layers up to about 1 μm thickness formed on stainless steels.

The unlubricated reciprocating sliding wear of a martensitic stainless steel in air and CO 2 between 20 and 300 °C

A limited programme of work has been undertaken to investigate the self-wear behaviour of a high strength martensitic stainless steel. This material is used as boiler tube supports in advanced gas-cooled reactors. Some tests were carried out in air at room temperature to permit comparison with data sets for other materials but most of the tests were in CO 2 in the temperature range 20–300 °C. Wear rates were measured by specimen weight loss and by continuous collection and intermittent weighing of wear debris. At room temperature, both in air and CO 2, specific wear rates were initially high, i.e. of the order of 10 −12 m 3 N −1 m −1. The severe wear rate however decreased with increasing temperature in CO 2 reaching a value of about 1 × 10 −13 m 3 N −1 m −1 at 300°C. Wear transitions were observed at all temperatures except 200 °C and resulted in a decrease in wear rate by between a factor of two and two orders of magnitude. The extent of the decrease in rate, however, showed no consistent trend with either temperature or load. Associated with the wear transition was a change in friction behaviour from widely fluctuating during the severe wear stage to smoother sliding in the post-transition stage. The duration of the severe wear stage at 20°C in CO 2 appeared to be proportional to load. A correlation was found between the initial wear kinetics and the mode of wear surface deformation. The highest wear rates occurred when the surface contact interactions resulted in gall formation; galling being defined as the displacement of material from one part of a surface to another region by a ploughing mechanism. The severe wear rate progressively decreased as the surface deformation mechanism changed to one of transfer from one surface to the other with the subsequent formation of features called prows. There was clear metallographic evidence that wear debris was generated by breakdown of these surface features.

The friction and sliding wear of unlubricated 316 stainless steel in air at room temperature in the load range 0.5–90 N

The reciprocating self-wear of 316 stainless steel in air and at room temperature has been investigated in the load range 0.5–90 N. Above approximately 40 N the debris was metallic, indicating a severe wear mode. The wear volume was a linear function of the sliding distance and the specific wear rate was independent of load. Below the 40 N load, after an initial severe stage, a transition occurred with a decrease in wear rate by up to an order of magnitude. The specific wear rate in both wear stages decreased with decreasing load, showing no indication of saturating at low loads. The load dependence of the wear volume V per unit sliding distance was of the form V = kL n where n ≈ 1.8 for both pre- and post-transition stages. The transition and the decreasing specific wear rates with decreasing load are thought to be associated with an increasing proportion of asperity interactions' being elastic rather than involving plastic deformation. It is proposed that wear occurs by a multistage mechanism of metal transfer to form prows, prow oxidation in the post-transition stage and prow breakdown. The transition is associated with a change in the rate-limiting step. This is believed to be the metal transfer step in the pre-transitional stage and the prow breakdown step in the post-transitional stage. Only a tentative correlation could be made between the onset of a wear transition and changes either in the friction behaviour or in the appearance of oxide in the wear debris. The friction data suggest that wear in the post-transition stage is a cyclic process of prow breakdown, prow re-formation by further metallic transfer, prow embrittlement by oxidation leading once again to breakdown and the formation of oxide-containing wear debris.

MICROSTRUCTURAL STUDY OF CYCLIC STRAIN HARDENING BEHAVIOUR IN BIAXIAL STRESS STATES AT ELEVATED TEMPERATURE

AbstractThis paper describes the cyclic strain hardening behaviour and dislocation structures of material in biaxial low cycle fatigue at elevated temperatures. In this study, push‐pull, reversed torsion and combined push‐pull/reversed torsion tests were carried out using a type 304 stainless steel in air. While there was no significant difference between the cyclic stress amplitudes in the push‐pull and reversed torsion tests on a von Mises' base, combination tests exhibited a 40% increase in stress amplitude. Most of the dislocations in the first two types of test adopted ladder or maze structures, while in the later case cells were found. Changing the loading mode at a certain cycle, for example, from push‐pull to reversed torsion, revealed that stress amplitude depended mainly on the concurrent applied strain mode and furthermore, that the strain mode before the interchange had little or no effect on the stress amplitude after the interchange. Tests were also performed in order to examine how prestrained material hardened in the three different loading modes, with the following results: prestrained material in push‐pull or in reversed torsion exhibited an anisotropic stress response, while the material in the combined tests exhibited an isotropic response. These cyclic responses are discussed in connection with the dislocation structure.

The influence of a 3.5% NaCl solution on the fatigue damage evolution in a planar slip f.c.c. stainless steel

The fatigue damage of a type 316L stainless steel in air and in 3.5% NaCl solution is analysed using observations of the evolution of the specimen surface roughness. The decrease in fatigue life in the corrosive solution is related to dissolution effects which favour a more rapid coalescence of the mechanically nucleated microcracks at the surface.

The sliding wear of 316 stainless steel in air in the temperature range 20–500°C

The friction and reciprocating wear of 316 stainless steel in air has been investigated in the temperature range 20–500°C at constant load using a standard pin and flat geometry. A marked change in wear behaviour occurred above 300°C. From room temperature to 300°C the wear rate decreased slowly with increasing temperature. This was accompanied by an increasing fraction of oxide in the wear debris. At 300°C the debris consisted entirely of oxide with the α Fe 2 O 3 structure. In this temperature range wear can be explained essentially in terms of mild wear. Above 300°C the wear rate decreased by an order of magnitude and was accompanied by a severely distorted wear surface. There was a high proportion of metallic particles in the wear debris. The surface roughening occurs at an early stage of wear and stops when glazed oxide regions form. The low wear rate is explained in terms of the high hardness of the glazed load-bearing areas and re-incorporation of wear debris into the wear scar.

Influence of loading conditions on fatigue crack growth rate in stainless steels in air and in sea salt solution

Influence of loading conditions on fatigue crack growth rate in stainless steels in air and in sea salt solution

The effects of saline aqueous corrosion on fatigue crack growth rates in 316 grade stainless steels

A study of fatigue crack propagation rates of 316 grade stainless steels in air and in an aqueous saline environment was carried out in an attempt to assess the fatigue properties encountered when such materials are used as surgical implants. The effects of variables such as temperature, pH, oxygenation level, bulk electrode potential, mean stress, frequency and stress waveform on the Paris crack growth law parameters were determined. Corrosion fatigue effects were observed in the aqueous saline environment, and a mechanism to describe this effect is proposed.

Long-Life Fatigue of Type 316 Stainless Steel at Temperatures up to 593°C

Some energy-system structural components may be subjected to 107 or more cycles of small-amplitude, strain-controlled vibrations. In such cases, information on the elevated-temperature, long-life (>106 cycles to failure) fatigue resistance of the austenitic steels often used in these components is needed. Present design guidelines provide fatigue curves for these steels only up to 106 cycles to failure. The objective of the present study was to evaluate the long-life fatigue resistance of one such steel, namely Type 316 stainless steel. Strain-controlled long-life (> 106 cycles to failure) fatigue experiments were conducted on solution-annealed Type 316 stainless steel in air at temperatures from 21 to 593° C. These were all for continuous cycling of smooth specimens under fully reversed straining (no mean stress). Results of this work provided a major advance in understanding the fatigue behavior of this steel. Tentative best-fit fatigue curves have been developed, but more data are needed to establish needed statistical confidence in them. At 21°C, strain and load-controlled experiments gave similar fatigue-resistance values at 108 cycles when inelastic straining was taken into account. However, at 427°C and above, strain-controlled cycling yielded fatigue-resistance levels at 108 cycles about 15 to 25 percent above those for load-controlled cycling. This difference is related to the continually increasing stress levels observed under strain cycling at the higher temperatures. That is, cyclic hardening continues to occur for 105 or more cycles of straining with accompanying two- to threefold increases in strength. This increased strength gives the increased fatigue resistance at long lives. Under load-controlled conditions, such cyclic hardening cannot occur, and the fatigue resistance is lower. Results of this work emphasize the need for considering the intended service conditions in carrying out laboratory experiments. The impact of these results on recommended experimental procedures for long-life fatigue testing of such alloys is discussed. Finally, considerations for application of these data in fatigue design are addressed.

ChemInform Abstract: THE INFLUENCE OF THE SURFACE ION IMPLANTATION OF ALUMINUM AND YTTRIUM ON THE OXIDATION BEHAVIOR OF A IRON‐15% CHROMIUM‐4% ALUMINUM STAINLESS STEEL IN AIR AT 1100°C

Chemischer InformationsdienstVolume 11, Issue 18 Physical Inorganic Chemistry ChemInform Abstract: THE INFLUENCE OF THE SURFACE ION IMPLANTATION OF ALUMINUM AND YTTRIUM ON THE OXIDATION BEHAVIOR OF A IRON-15% CHROMIUM-4% ALUMINUM STAINLESS STEEL IN AIR AT 1100°C M. J. BENNETT, M. J. BENNETTSearch for more papers by this authorM. R. HOULTON, M. R. HOULTONSearch for more papers by this authorG. DEARNALEY, G. DEARNALEYSearch for more papers by this author M. J. BENNETT, M. J. BENNETTSearch for more papers by this authorM. R. HOULTON, M. R. HOULTONSearch for more papers by this authorG. DEARNALEY, G. DEARNALEYSearch for more papers by this author First published: May 6, 1980 https://doi.org/10.1002/chin.198018025Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue18May 6, 1980 RelatedInformation

Effect of environment on crack growth behavior in austenitic stainless steels under creep and fatigue conditions

Crack growth behavior at high temperatures under cyclic, static, and combined loads was studied in annealed and 20 pct cold-worked Type 316 and 20 pct cold-worked Type 304 austenitic stainless steels in air and vacuum. Under cyclic load, crack growth rates in annealed Type 316 steel are slightly lower in vacuum than in air, but this difference decreases with increase in crack growth rate. Most importantly, the effect of temperature on crack growth is present even in vacuum and arises mostly from the variation of elastic modulus with temperature. In the cold-worked Type 316 steel, the pronounced hold-time effects on fatigue crack growth in air reported in the literature persists even in vacuum. This implies that at high crack growth rates these hold-time effects arise mostly from creep-fatigue interaction rather than environment fatigue interaction. Environment has a negligible effect also on crack growth under static load. Thus, time dependent crack growth in these steels is due to creep processes. Crack growth behavior in annealed and cold-worked materials are compared and reasons for the enhanced time dependent crack growth in cold-worked material are discussed in detail.

The fretting wear of an austenitic stainless steel in air and in carbon dioxide at elevated temperatures

The development of an experimental test facility designed to investigate the fretting wear of metals in high temperature gaseous atmospheres is described briefly. Small amplitude torsional fretting was produced between normally loaded annular contact surfaces at temperatures up to 650 °C. The information presented concerns the effects produced on fretting a type 321 stainless steel in air and CO 2 environments. Use of electron optical and surface profiling techniques has allowed a qualitative asessment of the degree and characteristic features of the damage to specimens fretted at room temperature and 650 °C under selected oscillatory wear conditions. During simultaneous oxidation and fretting at 650 °C the initially formed protective oxide is disrupted exposing a chromium-depleted surface which subsequently oxidizes to a less protective Fe-Cr spinel. This combination of effects could have unfortunate consequences on the long term wear behaviour.

オーステナイト・ステンレス鋼の疲れ強さにおよぼす雰囲気およびエポキシ樹脂被膜の影響

It was experimentally confirmed that improvement of fatigue strength of mild and high strength steels by epoxy-resin coating of notched part is attributed to its protective effect against oxygen and/or humidity in air. Fatigue strength improving effect of epoxy-resin coating may be wonder for austenitic stainless steel, because it is considerably stable for oxygen.Therefore the effects of atmosphere and epoxy-resin coating on the fatigue strength of 18-8 austenitic stainless steel are studied in this report. Plate bending fatigue testing machine is equiped in the atmosphere controlled chamber and rotating bending fatigue testing machine were used for these experiments.The results obtained are as follows.1) The S-N curve of 18-8 sautenitic stainless steel in air was almost the nearly that in dry nitrogen. Oxygen content in dry nitrogen and oxygen mixed atmosphere had no influence on a fatigue life of 18-8 austenitic stainless steel.2) Fatigue crack propagation rate of 18-8 austenitic stainless steel in air was also the same as that in dry nitrogen.These two points were quite different from the case of mild and high strength steels.3) Little effect of epoxy-resin coating was recognized on fatigue strength of austenitic stainless steel collared bar specimen.4) It can be concluded that the fatigue strength of austenitic stainless steel is not affected by oxygen and/or humidity in air at room temperature and little effect of epoxy-resin coating is expected on its fatigue strength.