Showing papers on "Maraging steel published in 2012"

Laser surface melting: A suitable technique to repair damaged surfaces made in 14 Ni (200 grade) maraging steel

Abstract: A high power solid Nd-YAG laser, operating in continuous mode, was used to re-melt the surface of a maraging steel, 14 Ni (200 grade), in different heat treatment conditions. Processing parameters were optimized for the employment of this technique as a repairing procedure of damaged surfaces to increase the useful life of tools made in maraging steels. Different zones can be found in laser-heated material. In addition, the absence of austenite reversion, consistent with the low nickel content of this steel, was found with the exception of a few very small pools of austenite found in a narrow layer in the heat-affected zone of samples corresponding to one of the studied heat treatment conditions of steel. Laser surface melting (LSM) combined with aging heat treatment causes a significant rise in the hardness (from 325 to more than 520 HV0.1) and in the wear resistance of the surface layer (with a decrease in the volume of lost material from 0.52 mm3 in the steel in the laser surface melted condition to 0.28 mm3 in the steel in laser surface melted and finally peak age hardening condition).

Key- Hole Plasma Arc Welding Of 8 Mm Thick Maraging Steel — A Comparison With Multi- Pass Gtaw

Abstract: Maraging steel is an iron nickel alloy with typical 18Ni-8Co-5Mo composition. It has low C martensitic structure which is strengthened by precipitation of inter-metallic compounds through ageing. Due to good fracture toughness in addition to high strength to weight ratio, the steel is widely used in aerospace applications. Conventionally we have been welding 8 mm-thick maraging steel with multi-pass automatic GTAW process. The steel shows “austenite reversion” phenomenon when heated to two phase (austenite + ferrite) region. Due to this phenomenon, maraging steel weld has two peculiar heat-affected zones; zone A nearest to the weld which is heated to fully austenitic region and zone B adjacent to it is heated to two phase region. Zone B contains reverted austenite which is not hardened by ageing. In conventional GTAW weld, zone B is quite wide, due to cumulative effect of multipasses. As zone B is not hardened fully by aging, it affects the mechanical properties of weldments. To reduce the width of the HAZ (zone B), single pass key-hole Plasma Arc Welding (PAW) was evaluated for 8 mm-thick plate. This paper describes the effect of weld passes and heat input on weld properties as a comparative study of single pass PAW and multi-pass GTAW. Mechanical properties (hardness, tensile properties, and fracture toughness) and macroscopic observations have been discussed. Also filler wire consumption & arcing time has being compared which are important aspects for production. The effect of single pass from multi-pass is very much visible in macroscopic observations. PAW weld shows significant reduction in width of HAZ (zone B) as compared to multi-pass GTAW. In aged condition in PAW weld does not show sudden drop in hardness in HAZ which is a common phenomenal in GTAW & the Improvement has been observed in tensile properties of PAW weld.

Microstructure and mechanical properties of low nickel maraging steel

Abstract: Austenitization with lower temperature and intercritical annealing were introduced in the treatment of a maraging steel with a composition of Fe–12.94Ni–1.61Al–1.01Mo–0.23Nb (wt.%). Scanning electron microscopy was employed to study the microstructure after austenitization at 950 °C and intercritical annealing, followed by aging at 485 and 600 °C. X-ray diffraction (XRD) analysis was applied to evaluate the formation of retained or reverted austenite. Thermodynamic calculation was employed to calculate equilibrium phase mole fractions. Hardness and Charpy impact toughness of the steel were measured. Intercritical annealing treatments did not result in significant increase of hardness either before or after aging. The Charpy impact toughness of the alloy in aged condition was enhanced after austenitization at 950 °C. No austenite was observed in XRD. However, suspected reverted austenite was found after austenitization at 950 °C followed by aging at 600 °C for 4 h. Relationships among heat treatment, microstructure and mechanical properties are discussed.

The corrosion inhibition of maraging steel under weld aged condition by 1(2E)-1-(4-aminophenyl)-3-(2-thienyl)prop-2-en-1-one in 1.5 M hydrochloric acid medium

Abstract: The influence of 1(2E)-1-(4-aminophenyl)-3-(2-thienyl)prop-2-en-1-one (ATPI) on the corrosion behavior of weld aged maraging steel in 1.5 M hydrochloric acid was studied by potentiodynamic polarization method and AC impedance (EIS) technique at different temperatures. The results showed that the inhibition efficiency of ATPI increased with the increase in the concentration of inhibitor and decreased with the increase in temperature. ATPI acts as a mixed type inhibitor without affecting the mechanism of the hydrogen evolution reaction or iron dissolution. The adsorption of ATPI on a weld aged maraging steel surface obeys the Langmuir adsorption isotherm equation. Both activation and thermodynamic parameters were calculated and discussed. ATPI inhibits the corrosion through both physisorption and chemisorption on the alloy surface. The surface morphology of the weld aged maraging steel specimens in the presence and the absence of the inhibitors was studied by the respective SEM images.

Real-time synchrotron X-ray diffraction study on the isothermal martensite transformation of maraging steel in high magnetic fields

Abstract: The isothermal austenite-to-martensite transformation kinetics in a maragingsteel have been studied by time-dependent microbeam diffraction measure-ments with high-energy X-rays. The transformation kinetics are shown to beaccelerated significantly when a magnetic field of 8 T is applied. The averagephase behaviour, obtained from a Rietveld refinement of the powder-averageddiffraction data, demonstrates that the martensite formation does not lead to amacroscopic strain in the austenite and martensite phases. An analysis ofindividual austenite reflections in the microbeam diffraction patterns, however,indicates that within the transforming austenite grains a transformation straindevelops asaresult ofthe formed martensite.Thedevelopment ofelastic strainsduring the transformation isexplained bya partial strain confinement within theuntransformed part of the austenite grain. The strain relaxation to thesurrounding austenite grains is found to be dependent on the austenite volume.For a set of individual austenite grains the martensite nucleation is correlatedwith the initial austenite volume and the strain developed prior to thetransformation as a result of martensite formation in the neighbouring grains.1. IntroductionMaraging steels form a class of low-carbon high-alloyed steelsdeveloped in the 1960s for applications requiring ultra-highstrength combined with good fracture toughness and corro-sion resistance. Their remarkable properties are obtainedthrough aprocessof martensite formation followed byan age-hardening treatment to form fine precipitates in the marten-siticmatrix(Slunderetal.,1968).Forsomemaragingsteelsthemartensite can be formed by an isothermal phase transfor-mation below room temperature (Holmquist et al., 1995; SanMartin et al., 2010). The time-dependent formation ofmartensite at a constant temperature was first observed byKurdjumov & Maksimova (1948, 1950) in an Fe–Mn alloy andhassubsequentlybeenreportedforseveralothersystems,suchas Fe–Ni–Cr and Fe–Ni–Mn alloys (Kakeshita et al., 1993a;Borgenstam & Hillert, 1997). More recently, isothermal time-dependent martensite formation has also been observed inother metal alloys (Sordelet et al., 2007; Jeffries et al., 2009a,b;Kustov et al., 2010; Lee et al., 2011) and ceramics (Pee et al.,2006). In all these systems the martensite fraction depends onboth time and temperature. In contrast, for the more commonathermal martensitic transformations the martensite fractionis independent of time and only governed by the lowesttemperature reached (Porter et al., 2009).The isothermal transformation from the austenite phase( ), with a face-centred cubic structure, into the martensitephase (

Microstructural Evolution and Mechanical Properties of Short-Term Thermally Exposed 9/12Cr Heat-Resistant Steels

Abstract: The microstructural evolution during short-term (up to 3000 hours) thermal exposure of three 9/12Cr heat-resistant steels was studied, as well as the mechanical properties after exposure. The tempered martensitic lath structure, as well as the precipitation of carbide and MX type carbonitrides in the steel matrix, was stable after 3000 hours of exposure at 873 K (600 °C). A microstructure observation showed that during the short-term thermal exposure process, the change of mechanical properties was caused mainly by the formation and growth of Laves-phase precipitates in the steels. On thermal exposure, with an increase of cobalt and tungsten contents, cobalt could promote the segregation of tungsten along the martensite lath to form Laves phase, and a large size and high density of Laves-phase precipitates along the grain boundaries could lead to the brittle intergranular fracture of the steels.

High-strain-rate behavior of maraging steel linear cellular alloys: Mechanical deformations

Abstract: The high-strain-rate deformation response of 25% dense linear cellular alloy (LCA) structures made from high-strength high-toughness maraging 250 steel is investigated. Constitutive parameters for the Johnson–Cook strength model for this steel are determined and validated by correlating final and transient deformation states obtained from experiments on solid maraging 250 steel cylinders impacting a rigid high-strength steel anvil, with those predicted using AUTODYN-3D Lagrangian based finite element simulations. The constitutive parameters are then used to predict the deformation response of a 9-cell waffle-design LCA under axial impact against a rigid anvil. Experiments performed on the LCA structure under the same impact conditions reveal that the qualitative deformation response correlates well with simulations, indicating the unique response of the LCA structures is well captured by the validated Johnson–Cook model parameters.

Effect of Diacetyl Monoxime Thiosemicarbazone on the Corrosion of Aged 18 Ni 250 Grade Maraging Steel in Sulphuric Acid Solution

Abstract: The corrosion inhibition of the aged 18 Ni 250 grade maraging steel in 0.5 M sulphuric acid by diacetyl monoxime thiosemicarbazone (DAMTSC) at 303–323 K has been investigated by potentiodynamic polarization, EIS, and SEM techniques. Good inhibition efficiency of DAMTSC was revealed even at low concentrations, which increased with the increase in DAMTSC concentration and decreased with the increase in temperature. The activation energies, , as well as other thermodynamic parameters (; ; ), were evaluated and discussed. The adsorption of DAMTSC on the aged maraging steel surface was found to obey the Langmuir adsorption isotherm model and shows mixed type inhibition behavior.

Corrosion Inhibition of the Annealed 18 Ni 250 Grade Maraging Steel in 0.67M Phosphoric Acid by 3,4-Dimethoxybenzaldehydethiosemicarbazone

Abstract: 18 Ni 250 grade maraging steel is a potential high strength steel for advanced technologies such as aerospace, nuclear, and sporting goods The corrosion inhibition of the aged 18 Ni 250 grade maraging steel in 067 M phosphoric acid by 3,4 dimethoxybenzaldehydethiosemicarbazone (DMBTSC) has been investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques The effect of concentration of inhibitor and solution temperature on inhibition efficiency of the inhibitor was studied DMBTSC inhibits corrosion even at very low concentration Polarisation curves indicate mixed type inhibition behavior affecting both cathodic and anodic corrosion currents The mechanism of inhibition was discussed on the basis of an adsorption isotherm, as well as calculated thermodynamic parameters Adsorption of DMBTSC on the annealed maraging steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibb’s free energy values confirm the spontaneous adsorption

Effect of Tube Spinning With Subsequent Heat-Treatment on Performance and Microstructure Evolution of T250 Maraging Steel

Abstract: The effects of spinning deformation and subsequent heat treatments on the mechanical properties and microstructure of 18Ni Co-free Maraging steel (T250) tube were evaluated comparatively with the perform An obvious radial shrinkage is detected in spun tubes after heat treatment and the magnitude of the shrinkage induced by solution treatment is almost the same as that by aging Plastic deformation during spinning elongated the grains severely in the direction of metal flow The solution treatment resulted in a drastically refined grain and recrystallised microstructure, removing the effect of plastic deformation, relieving the tangential residual stress and strain and improving hardness Subsequent aging obtained a tempered microstructure, enhancing hardness values strikingly for precipitation strengthening XRD (X-ray diffraction) analysis indicated that the reversed austenite formed in a plate-like along the grain boundaries and the volume fraction of austenite in spun tube was more than double that in the preform These results imply that the residual stress and stain induced by spinning process and reversed austenite forming during aging might have the similar contribution to the radical shrinkage

Ultra-strength and high toughness maraging steel and manufacturing method thereof

Abstract: The invention provides ultra-strength and high toughness maraging steel and manufacturing method thereof. The maraging steel comprises the following chemical components: less than or equal to 0.03 weight percent of C, less than or equal to 0.10 weight percent of Mn, less than or equal to 0.10 weight percent of Si, less than or equal to 0.05 weight percent of S, less than 0.010 weight percent of P, 17.50 to 20.50 weight percent of Ni, 2.00 to 4.00 weight percent of Mo, 1.00 to 1.75 weight percent of Ti, 0.05 to 0.15 weight percent of Al, 0.0005 to 0.002 weight percent of B, 0.005 to 0.10 weight percent of Zr+Ca, and the balance of Fe and inevitable impurities. By adopting Ni-Mo-Ti-Al alloying, the maraging steel meets the requirements of good comprehensive properties such as high strength and toughness, which is suitable for high-end products such as thin-wall parts, high-grade moulds and springs.

CORROSION BEHAVIOR OF 18% Ni M250 GRADE MARAGING STEEL UNDER WELD-AGED CONDITION IN SULFURIC ACID MEDIUM

Abstract: The corrosion behavior of 18% Ni M250 grade maraging steel under weld-aged condition was investigated in sulfuric acid medium of different concentrations (0.1–2 M) at different temperatures (30°–60°C). Electrochemical measurements were carried out using the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results showed an increase in the corrosion rate with the increases in temperature as well with increase in the concentration of the corrosion medium. The results obtained from the Tafel extrapolation technique and electrochemical impedance spectroscopy were in good agreement. Activation parameters were evaluated using the Arrhenius equation and transition state equation. The surface morphology of the corroded specimen was compared with that of the un-corroded sample by using scanning electron microscopy (SEM).

Significant enhancement of strength in a lamellar-type nanostructured maraging steel subjected to equal-channel angular pressing for 12 passes

Abstract: An overall lamellar-type nanostructure was successfully obtained in maraging steel via equal-channel angular pressing (ECAP) for 12 passes at room temperature. After subsequent ageing treatment (440–500 °C), the nano-thick martensite lamellae still survived, while the high density nano-precipitates emerged within them uniformly. By ECAP and subsequent aging treatment, very high tensile strength (2400–2700 MPa) was achieved in comparison with the general strength of 1985 MPa. The influences of ECAP and aging treatment on the microstructures and tensile strength were discussed qualitatively.

Cold brittleness of corrosion-resistant maraging steel 08Kh15N5D2T

Abstract: Results of a study of the effect of the method of remelting and of heat treatment modes on the behavior of serial curves of impact toughness and on the position of cold-shortness threshold in steel 08Kh15N5D2T are presented.

Dynamic deformation and fragmentation response of maraging steel linear cellular alloy

Abstract: The dynamic deformation and fragmentation response of 25% dense 9-cell linear cellular alloy (LCA) made of unaged 250 maraging steel, fabricated using a direct reduction and extrusion technique, is investigated. Explicit finite element simulations were implemented using AUTODYN finite element code. The maraging steel properties were defined using a Johnson-Cook strength model with previously validated parameters. Rod-on-anvil impact tests were performed using the 7.6mm helium gas gun and the transient deformation and fragmentation response was recorded with highspeed imaging. Analysis of observed deformation states of specimens and finite element simulations reveal that in the case of the 9-cell LCA, dissipation of stress and strain occurs along the interior cell wells resulting in significant and ubiquitous buckling prior to confined fragmentation.

Effect of annealing on the structure and mechanical properties of the maraging steel N9K17M14-nanoamorphous alloy Co 69 Fe 4 Cr 4 Si 12 B 11 composite material

Abstract: The effect of annealing on the structure, mechanical properties, and fracture of a one-dimensional composite material consisting of a microwire made of maraging N9K17M14 steel with a surface layer of a eutectic soft magnetic Co69Fe4Cr4Si12B11 alloy is studied. The optimum temperature of annealing of the composite material is found; as a result, high strength characteristics are achieved at good plasticity. The composite material with a nanoamorphous layer is shown to have the high strength characteristics of the matrix maraging steel at significantly higher plasticity. When the Co69Fe4Cr4Si12B11 alloy is deformed in the composition of the composite material, it exhibits a plasticity effect, and this alloy fails in a brittle manner when deformed in the form of a wire or a ribbon. This effect becomes more pronounced upon annealing.

Gas nitriding method for maraging steel

Abstract: PROBLEM TO BE SOLVED: To provide a gas nitriding method for maraging steel by which residual stress is sufficiently imparted to the maraging steel to improve its fatigue characteristic by increasing the thickness of a nitriding layer to be formed on the surface layer of the maraging steel, while preventing the generation of a white layer.SOLUTION: A gas nitriding method for maraging steel includes a step of heating the maraging steel in an atmosphere containing an ammonia gas, wherein the atmosphere containing an ammonia gas has nitriding potential of ≥0.2 and ≤2.0 and the heating temperature is ≥480°C and ≤500°C.

Development of 18Ni maraging steel for SMAW

Abstract: A new type of repair electrode for 18Ni maraging steel was developed.Proper chemistry ingredient of core wire and coating was determined.A series of welding experiments and mechanical tests of this electrode were performed.Microstructure and fracture appearance were analyzed by OM,SEM,TEM.The results showed that the electrode had good weldability,small splash and good detachability.After aging treatment,the deposit metal had excellent mechanical properties,low phosphorus,sulphur and diffusible hydrogen content,which was fit in with base metal.

Dynamic Recrystallization of 18Ni(1700MPa) Maraging Steel During Hot Deformation

Abstract: Dynamic recrystallization(DRX) behaviors of 18Ni maraging steel during hot deformation have been investigated by single-pass thermo-mechanical simulative experiment at temperatures of 1173K-1323K and strain rates of 0.001s-1-1s-1. The results show that the true stress-true strain curves type of this alloy is DRX. The DRX in 18Ni maraging steel is easy to occur at low strain rates and high deformation temperatures. Using regression analysis, the activation energy(Q) for DRX of 18Ni maraging steel was calculated to be 413544.96J/mol. The constitutive equation of peak stress for DRX was also obtained. The mathematical models of critical stress and critical strain were finally established.

Effects of Aging Condition and Humidity on Fatigue Properties of Maraging Steel

Abstract: 1 緒 言 マルエージング鋼は実用鋼中最も静強度が高く,しか もじん性に優れた材料である.しかし高価なためその使用 範囲は限ずしも多くはない.すなわち,航空機やロケッ ト,人工衛星などの宇宙開発用機器,身近には自動車の 無段変速機の金属ベルト等,特に過酷環境下において十 分な強度が要求される機器用部材として使用されること が多く,そこでは高強度だけでなく高い強度信頼性が求 められている.一般に高強度金属材料は,欠陥や湿度に 敏感であり,1)~ 3)マルエージング鋼も同様である.そのた め,本鋼の切欠き感度については詳細な研究が行われて いる.4)著者らはこれまで,マルエージング鋼の基本的な 疲労特性の把握,5), 6)さらに疲労強度改善法について,表 面処理 7)~ 9)と微視組織の調整 10), 11)の両面から検討して きた.例えば微視組織の調整の面からは,過時効処理に より逆変態オーステナイトを生成させれば疲労強度は向 上すること,この効果は湿度に対する感度低下にも有効 であることを報告した.さらに本材の時効処理は通常所 定の温度と時間で一回だけ行うが,その時効に加えて, さらに比較的低温で再時効,すなわち二回目の時効を行 えば,湿度に対する感度は低下することも報告した.12)し かし,それに関する研究は他にみられず,著者らによる 限られたデータのみで,さらなるデータの蓄積が必要で ある.また湿度敏感性に対する二回の時効処理による効 果の詳細についても未解明であった. そこで本研究では,以上述べた著者らの結果を考慮し て,マルエージング鋼の時効条件を幅広く変えることに より,静的な機械的性質と疲労特性を調べ,通常の一回 の時効材における結果との比較のもとに二回目の時効処 理の影響,特に高湿度下における疲労特性に対する二回 時効処理することの有効性を検討するため,湿度を制御 した環境中で回転曲げ疲労試験を行い,詳細なき裂伝ぱ 過程の表面観察と破面観察を行った. 2 材料,試験片および実験方法 用いた材料は市販の 350級 18%Niマルエージング鋼 (直径 13mmの丸棒)である.化学成分を Table 1に示 す.納入材に,溶体化処理 (1123K, 5.4ks) を行った後, 各種時効組織を得るため時効条件を変えて熱処理した. 特に本研究では,時効条件として通常適用される 753K での 1回の時効(以下,一段時効)に加え,その時効温 度で最高硬度を示した後さらに低温の 673Kで 2回目の 時効(以下,二段時効)も行った.なお,溶体化後の旧 オーステナイト平均結晶粒径は約 20μmであった. Fig. 1に,引張試験および疲労試験に用いた試験片の マルエージング鋼の疲労特性に及ぼす時効条件と湿度の影響 皮籠石 紀 雄 林 光 介 永 野 茂 憲 中 村 祐 三 森 山 三千彦 前 田 義 和 Effects of Aging Condition and Humidity on Fatigue Properties of Maraging Steel

Type Certification of 18 Ni Maraging Steels for Landing Gears

Abstract: Maraging steels exhibit unique properties, such as high strength with excellent fracture toughness, ease of machining and above all distortion free thermal processing. These attractive properties and advantages of maraging steel do not outweigh the initial cost resulting from high alloy content and especially in certain structural components where in much of the forging is machined as swarf. However, with the constant drive to prove the technology when maximum strength and stiffness per unit volume becomes the major criteria, the choice of material may overwhelmingly become maraging steel. Above requirements necessiate a landing gear material for Indian fighter aircraft to have a combination of high strength, sufficient stiffness, excellent fatigue strength, utmost cleanliness, resistance to micro-structural degradation, freedom from surface anomalies, good corrosion & stress corrosion resistance and superior toughness to meet the current damage tolerant design criteria. M/s Midhani in consultation with airworthiness authorities took up the task to develop & manufacture this steel to the laid down type test schedule. The steel has satisfactorily met all the requirements and landing gear has been successfully forged, machined and fitted to the prototype. This paper describes the metallurgical aspects that are relevant for developing the maraging steel along with a brief note on the properties - chemical, microstructural and mechanical. An attempt is made in the presentation to show that the indigenously developed and produced maraging steel is indeed at par with aeronautical grade materials, including maraging steels of international sources.

Method of straightening thin-wall cylindrical articles from maraging steels

Abstract: FIELD: process engineering. ^ SUBSTANCE: invention relates to machine building and may be used for straightening cylindrical maraging-steel thin-wall articles. To ensure required diametral sizes of thin-wall cylindrical articles from maraging steel, split mandrel as-hardened from alloyed steel is fitted on article, its thermal linear expansion factor being lower than that of the article in the entire temperature range of heating it to maraging temperature. Mandrel is composed of two halves tightened together by common axle with no clearances while opposite ends are bolted together in fitting it on article. Split mandrel ID is selected to equal article OD. In joint heating, hold and cooling in whatever time, interference between mandrel and article is maintained. In maraging, article is hardened while article shape set by mandrel is preserved. After cooling of mandrel-article system in air, mandrel is withdrawn. ^ EFFECT: provision of required diametral sizes. ^ 2 tbl, 1 ex

Maraging steel and maraging steel used for metal belt

Abstract: The invention provides maraging steel used for a metal belt. The maraging steel can reduce the composition forming the starting point TiN of a fatigue failure in a high-cycle region, and nitrogen treatment is easy to perform to improve surface hardness; moreover, the compressive residual stress of a surface nitride layer is increased to improve the bending fatigue strength; in addition, the maraging steel is also used for the micronization of old austenitic grain which ensures high strength and ductility. The maraging steel is characterized by comprising the following components in percent by mass: less than 0.01 percent of C, less than 0.1 percent of Si, less than 0.1 percent of Mn, less than 0.01 percent of P, less than 0.005 percent of S, 17.0 to 22.0 percent of Ni, 0.1 to 4.0 percent of Cr, 3.0 to 7.0 percent of Mo, greater than 7.0 percent and less than 20.0 percent of Co, less than 0.1 percent of Ti, less than 2.5 percent of Al, less than 0.03 percent of N, less than 0.005 percent of O, less than 0.01 percent (excluding 0 percent) of B, 8.0 to 15.0 percent of Co/3+Mo+4Al, and the balance Fe and unavoidable impurities.

Acoustic emission during tensile deformation of M250 grade maraging steel

Abstract: Acoustic emission (AE) generated during room temperature tensile deformation of varyingly heat treated (solution annealed and thermally aged) M250 grade maraging steel specimens have been studied. Deformation of microstructure corresponding to different heat treated conditions in this steel could be distinctly characterized using the AE parameters such as RMS voltage, counts and peak amplitude of AE hits (events).