Structure and corrosion resistance of oxides grown on maraging steel in steam at elevated temperatures

doi:10.1016/S0169-4332(96)00587-9

Applied Surface Science

Volume 108, Issue 1, January 1997, Pages 159-165

https://doi.org/10.1016/S0169-4332(96)00587-9 Get rights and content

Abstract

The microstructure of oxides formed on 250 maraging steel in steam at elevated temperatures was established. The coating consisted of at least two sub-layers, an innermost layer of austenitic phase and a layer of magnetite Fe₃O₄. When low loads of steel were used, a third top layer of hematite Fe₂O₃ was found. The coating provides good protection against atmospheric corrosion, which was significantly better than phosphating.

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Plates of Maraging-300 steel with a chemically grown layer on the surface were prepared by heat treatment in superheated steam at different times. The grown coating on the martensitic substrate was characterized in terms of thickness, compositional and structural information by means of optical and scanning electron microscopies and by Grazing Incidence X-ray Diffraction (GIXRD). The results showed the presence of the hematite, magnetite, and austenite crystalline phases in two different sublayers composing the entire reacted layer: an austenite sublayer over the maraging substrate, and an oxide sublayer at the top, right above the austenite layer, composed of interspersed hematite and magnetite. Quantitative Phase Analysis by the Rietveld method under GIXRD was used to obtain the thicknesses of multiphase chemically reacted layers. The methodology and mathematical formalism are described. The comparison with estimated values from optical and scanning electron microscopy have shown a good agreement between the imaging and diffraction techniques, suggesting that the reacted layer increases progressively with the heat treatment time.
Schiff Bases Derived from Triazoles as Corrosion Inhibitors for Maraging Steel in Acid Mixtures: Experimental and Theoretical Studies
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The ability of two triazole derived Schiff bases, namely,4-[(furan-2-ylmethylidene)amino]-5-methyl-4H-1,2,4-triazole-3-thiol [FAMTT] and 4-[(4-chlorobenzylidene)amino]-5-methyl-4H-1,2,4-triazole-3-thiol [CAMTT], to inhibit corrosion of maraging steel by 2:1 mixture of HCl and H₂SO₄ was evaluated. Temperature range of 30-45 °C and inhibitor concentration range of 5-25 ppm for FAMTT and 5-50 ppm for CAMTT were employed. An increase in inhibitor concentration and temperature resulted in an increase of inhibition efficiencies of both inhibitors. The inhibition efficiencies of FAMTT were significantly larger than CAMTT in weight loss studies, a maximum of 94.4% observed at 25 ppm for FAMTT and a maximum of 82.4% at 50 ppm observed for CAMTT. However, in the electrochemical studies, though FAMTT performed better than CAMTT, the differences in their efficiencies were somewhat less than that observed in weight loss method. In polarization studies, FAMTT showed maximum efficiency of 96.2% at 25 ppm and 45 °C, while, CAMTT showed a maximum of 90.8% at 50 ppm and 45 °C, and, in electrochemical impedance studies (EIS), maximum efficiency was 97.4% at 25 ppm and 45 °C for FAMTT, and 96.5% at 50 ppm and 45 °C for CAMTT. Inhibition properties of both were verified by kinetic and thermodynamic analyses. Both exhibited mixed type inhibitory action by chemisorbing on the metal surface and followed Langmuir adsorption isotherm. The adsorption of the inhibitors on the steel surface was confirmed by Scanning Electron Microscopy-Energy-dispersive X-ray studies (SEM-EDS) analyses. Density Functional Theory (DFT) calculations were made to predict the inhibition property, and to correlate molecular structure with the corrosion inhibition property. There was a good agreement between experimental observation and theoretical prediction- that FAMTT has higher inhibition potential than CAMTT.
A critical review on susceptibility of stress corrosion cracking in maraging steel weldments
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Citation Excerpt :
The material has been tested for 25 days and it has found that there were no decrease in stress intensity value for hydraulic oil compare to water. The microstructure of oxides forms on steam at a certain temperature on maraging steel was established, which is beneficial for SCC resistance [21]. It has been observed that the steam therapy offers higher resistance to maraging steel than standard manganese phosphate therapy because subsequent therapy makes steel more susceptible to SCC [22].
Stress corrosion cracking is the decay of mechanical characteristics of sensitive material under the mixed effects of stress and corrosive atmosphere. Because of their high strength and extremely good fracture toughness 18 Ni maraging steel (250 grade) is suitable for aerospace application such as rocket engines as these steel materials can be welded without much hassles over a broad range of thickness. The maraging steel weldment causes catastrophic failure during service owing to stress corrosion cracking. It is a challenge to comprehend the SCC behaviour for the weldment of this material. The attempts of this review paper are to analyse the mechanical and microstructural changes related to SCC due to some post weld heat treatment or surface modifications. Further, review was made to intuit the effect of different welding processes on SCC behaviour of this material. Apart from a brief review of 18 Ni maraging steel, this paper presents the impact of different corrosive environments on SCC activity. The effect of different filler materials and composition of the filler material were also investigated.
Modelling of corrosion fatigue crack initiation on martensitic stainless steel in high cycle fatigue regime
2018, Corrosion Science
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AES Measurements were performed at ten different locations on the specimen surface in order to evaluate the thickness uniformity of the passive film. The half of the oxygen content in the passive film is considered [44,45] as the corresponding thickness of passive film (see Fig. 3) and was found to be uniform on the specimen surface. Its value is around 3 nm for the passive film formed in air.
This paper presents an analytical model for assessing the corrosion fatigue crack initiation life on a martensitic stainless steel X12CrNiMoV12-3 in high cycle fatigue regime (between 10⁵ and 10⁷ cycles). Based on in-situ electrochemical measurements during corrosion fatigue tests in NaCl aqueous solution, the corrosion fatigue crack initiation mechanism was identified. Two main stages were investigated: (i) the fracture of the passive film by slip bands and (ii) the free dissolution of the metal developing fatigue crack initiation from a critical corrosion defect. The depassivation stress threshold corresponds to the median fatigue strength at 10⁷ cycles for fatigue corrosion tests. For an applied stress range less than this threshold, the depassivation phenomenon was not observed at 10⁷ cycles and no crack initiation occurred. The proposed model takes into account the depassivation process induced by the slip bands emergence at the specimen surface and the corrosion rate under cyclic loading. The experimental results are compared to the proposed model taking into account mechanical and electrochemical material parameters.
Simultaneous ageing and plasma nitriding of grade 300 maraging steel: How working pressure determines the effective nitrogen diffusion into narrow cavities
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Citation Excerpt :
Maraging steels show exceptional strength to toughness ratio, good machinability and weldability and ease of heat treatment. Moreover, the retention of their mechanical properties after long operative times at medium-high temperatures can be outlined as one of the most interesting characteristics [1–4]. These properties can be explained by the particular chemical composition of these alloys and its hardening treatment.
Maraging steels combine excellent mechanical properties at medium-high temperatures with good fracture toughness, but they usually require the aid of thermochemical treatments to enhance superficial properties such as resistance to abrasive wear and corrosion resistance. In particular, plasma nitriding, due to its duration and temperature, which are compatible with the age-hardening cycles of maraging steels, permits the realization of both processes simultaneously.
In this work, simultaneous ageing and arc-activated plasma nitriding of maraging steel grade 300 were studied as a function of the working pressure of the gases (N₂ and Ar) present in the vacuum reactor chamber. In addition, the influence of the operating pressure was established by analysing the capacity of the plasma to penetrate in 2.5 mm in diameter blind holes.
In-depth chemical composition, hardness and micro-hardness profiles, X-Ray diffraction, roughness, tribological characterization and corrosion tests were carried out to compare maraging steel samples treated in one simultaneous plasma nitriding and ageing process and in two-step processes. Metallographic tests and nanoindentation measurements were performed to study how the plasma penetrates and diffuses into the blind holes and how the nitride case layer thickness formed at the inner surfaces of the holes changes as a function of the distance to the surface for various working pressures.
Microstructure and corrosion behaviour of gas tungsten arc welds of maraging steel
2015, Defence Technology
Citation Excerpt :
Jha et al. [10] studied SCC of maraging steel and found that an intergranular mode of cracking occurs. Study made on 250 grade maraging steel at elevated temperature in steam has shown that it offers better protection compared to manganese phosphate treatment [11]. SCC susceptibility of steel was caused by acid dip step in the pretreatment of phosphating process [12].
Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding (GTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking (SCC). The present study is aimed at studying the SCC behaviour of MDN 250 (18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using GTAW process. Post-weld heat treatments of direct ageing (480 °C for 3 h), solutionizing (815 °C for 1 h) followed by ageing and homogenizing (1150 °C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of GTA welds of MDN 250 Maraging steel.

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Structure and corrosion resistance of oxides grown on maraging steel in steam at elevated temperatures

Abstract

Corros. Sci.

Corros. Sci.

JISI

Scr. Met.

Oxid. Met.

Harterei Technische Mitteilungen