Showing papers on "Maraging steel published in 2011"

The influence of tempering temperature on the reversed austenite formation and tensile properties in Fe–13%Cr–4%Ni–Mo low carbon martensite stainless steels

Abstract: The influence of tempering temperature on the reversed austenite formation and tensile properties are investigated in Fe-13%Cr-4%Ni-Mo low carbon martensite stainless steel in the temperature range of 550-950 degrees C. It is found that at the temperatures below 680 degrees C, the reversed austenite formation occurs by diffusion. Amount of the reversed austenite is determined I:IN the tempering temperature and the holding time. The segregation of Ni is the main reason for the stability of the reversed austenite. When the temperatures are above 680 degrees C, the reversed austenite formation proceeds by diffusionless. The reversed austenite will transform back to martensite after cooled to room temperature. The tensile properties are most strongly influenced by the amount of the reversed austenite obtained at room temperature. The excellent combination of good strength and ductility is at 610 degrees C. (C) 2011 Elsevier B.V. All rights reserved.

3,4-Dimethoxybenzaldehydethiosemicarbazone as corrosion inhibitor for aged 18 Ni 250 grade maraging steel in 0.5 M sulfuric acid

Abstract: The corrosion inhibition of the aged 18 Ni 250 grade maraging steel in 0.5 M sulfuric acid by 3,4-dimethoxybenzaldehydethiosemicarbazone(DMBTSC) has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) techniques. The inhibition efficiency increased with the increase in inhibitor concentration and decreased with the increase in temperature. Polarization curves indicated mixed type inhibition behavior affecting both cathodic and anodic corrosion currents. The thermodynamic parameters of corrosion and adsorption processes were evaluated. The adsorption of DMBTSC on the aged maraging steel surface was found to obey the Langmuir adsorption isotherm model, and the calculated Gibb’s free energy values confirm the spontaneous adsorption. The results obtained by the two techniques were in good agreement.

Strengthening behavior of Fe–Cr–Ni–Al–(Ti) maraging steels

Abstract: In the present work a Ti-free and Ti-containing stainless maraging steel of type PH13-8 Mo were investigated with respect to their mechanical properties. Particular attention was given to the stress–strain behavior during tensile tests in correlation to the developed precipitates and austenite at differently aged conditions. Both alloys show a strong increase in strength from the very beginning of aging with the typical stress–strain behavior of maraging steels, whereas the Ti-containing alloy suffers from severe intergranular embrittlement at short aging times. Embrittlement of the Ti-containing steel grade is attributed to the significantly higher volume fraction of precipitates in the early stages of aging when compared to the Ti-free steel grade. Overaging leads to distinct work hardening in the Ti-containing alloy, which is caused by the evolution of the precipitates and the formation of reverted austenite.

Microstructural control of maraging steel C300

Abstract: The microstructure evolution and precipitation kinetics of maraging steel C300 have been studied in the aging temperature range from 400 to 600°C. The relation between mechanical properties and precipitation hardening response is explained, and modelling is used to optimise the properties. Ultrafine needle shaped Ni3Ti phase is the main strengthening precipitate in maraging C300, and it shows very high resistance to coarsening. A spherically shaped Fe2Mo phase is formed at higher temperatures and in the overaged condition. Inter- and intralath reverted austenite nucleates at higher temperature (∼600°C). Rolling and aging treatment can produce the highest hardness by a combination of work hardening and precipitation strengthening. Microstructural evolution simulation using Monte Carlo modelling has been applied to this alloy, and the modelling has been validated by the experimental results.

Characterization of Nano‐Sized Precipitates in a Mn‐Based Lean Maraging Steel by Atom Probe Tomography

Abstract: We present atom probe tomography results of a precipitation-hardened Mn-based maraging steel (9 Mn, 1.9 Ni, 0.6 Mo, 1.1 Ti, 0.33 Al; in at.%). The alloy is characterized by the surprising effect that both, strength and total elongation increase upon aging. The material reveals a high ultimate tensile strength (UTS) up to 1 GPa and good ductility (total elongation (TE) of up to 15% in a tensile test) depending on aging conditions. We map the evolution of the precipitates after 450 °C aging treatment using atom probe tomography in terms of chemical composition and size distribution.

Development of an ultrahigh strength low alloy steel for armour applications

Abstract: The present paper describes a steel with yield strength exceeding 1900 MPa and fracture toughness in the range of 40–50 MPa m1/2, in its optimum heat treated condition. Its strength is similar to that of 18 Ni (300) grade of maraging steel with good fracture toughness. When tempered at 300°C, it shows tempered martensite along with a small amount of retained austenite phase. The steel shows nearly 25% reduction in weight over typical rolled homogeneous armour (RHA) steel against high velocity hard steel core projectiles. The processing, microstructure, mechanical and ballistic properties of the steel are demonstrated.

Laser Cladding and Heat Treatment of Ni–Co–Mo Maraging Steel

Abstract: The subject of this paper is a surface-integrity analysis of Ni–Co–Mo laser cladded maraging steel (EN 10027-2, W. No. 1.2799). Experiments were performed on 3.3 kW Nd:YAG laser system with coaxial injection of Ni–Co–Mo powder alloy that integrates various modes of laser beam guidance and different degrees of overlapping. The specimens were subsequently solution and precipitation annealed in order to examine a precipitation hardening of the newly formed material using the scanning electron microscopy (SEM) with a microprobe for energy-dispersive spectroscopy analysis, supported by microhardness tests. The residual stresses were determined by a hole-drilling method, using the integral method for residual stresses calculation. Favourable compressive residual stresses are generated in laser cladded layers due to a phase transformation from austenite to lath-martensite. The optimal selection of laser cladding process parameters enables efficient and cost-effective maintenance of damaged surfaces on the vital parts of die-casting tools, made from 1.2799 maraging steel.

Ultrahigh Strength Steel: Development of Mechanical Properties Through Controlled Cooling

Abstract: Structural steels with very high strength are referred as ultrahigh strength steels. The designation of ultrahigh strength is arbitrary, because there is no universally accepted strength level for this class of steels. As structural steels with greater and greater strength were developed, the strength range has been gradually modified. Commercial structural steel possessing a minimum yield strength of 1380 MPa (200 ksi) are accepted as ultrahigh strength steel (Philip, 1990). It has many applications such as in pipelines, cars, pressure vessels, ships, offshore platforms, aircraft undercarriages, defence sector and rocket motor casings. The class ultrahigh strength structural steels are quite broad and include several distinctly different families of steels such as (a) medium carbon low alloy steels, (b) medium alloy air hardening steel, (c) high alloy hardenable steels, and (d) 18Ni maraging steel. In the recent past, developmental efforts have been aimed mostly at increasing the ductility and toughness by improving the melting and the processing techniques. Steels with fewer and smaller non-metallic inclusions are produced by use of selected advanced processing techniques such as vacuum deoxidation, vacuum degassing, vacuum induction melting, vacuum arc remelting (VAR) and electroslag remelting (ESR). These techniques yield (a) less variation of properties from heat to heat, (b) greater ductility and toughness especially in the transverse direction, and (c) greater reliability in service (Philip, 1978). The strength can be further increased by thermomechanical treatment with controlled cooling.

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

Abstract: Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo, Ti) Laves phase particles, which are stable at high temperatures These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment

Deformation and fracture of a composite material based on a high-strength maraging steel covered with a melt-quenched Co 69 Fe 4 Cr 4 Si 12 B 11 alloy layer

Abstract: Multifractal analysis is used to study the deformation and fracture of a promising composite material consisting of a wire base made of K17N9M14 maraging steel covered with a surface layer made from a Co69Fe4Cr4Si12B11 amorphous alloy. As compared to its components, this material has a substantially better set of the mechanical properties.

Influence of filler material composition on residual stress distribution of dissimilar gas tungsten arc weldments of ultrahigh strength steels

Abstract: The influence of filler material composition on the residual stress distribution in similar and dissimilar gas tungsten arc weldments of maraging steel and medium alloy medium carbon steel has been investigated. In the fusion zone, residual stresses are compressive in similar metal welds of maraging steel and tensile in similar metal welds of medium alloy medium carbon steel. In the dissimilar metal welds, the nature of residual stresses in the weld varied from compressive in maraging steel to tensile in medium alloy medium carbon steel. The magnitude of residual stresses decreased when the maraging steel is taken in soft condition in the dissimilar metal welds. Post-weld aging resulted in lowering of residual stresses in medium alloy medium carbon steel.

Elevation of reliability characteristics of maraging steel 03N18K9M5T by creating a "nanotriplex"-type structure

Abstract: Characteristics of mechanical strength of maraging steel N18K9M5T after various variants of heat treatment are studied. The treatment mode providing a structure with retained austenite and two types of reverted austenite is determined. An optimum structure ensuring enough strength at high impact toughness and static and cyclic crack resistances is chosen.

Ultrahigh-Strength Nanostructured Steels for Armours

Abstract: The paper presents principles of designing and examination results of superclean high-strength new generation maraging steel for composite armours protecting against piercing with small-calibre armour-piercing (AP) projectiles. The research concerns maraging steel of yield strength ≥ 2,5 GPa and suitable toughness required to achieve high resistance of armour to piercing with AP projectiles. Three base compositions of maraging steel (MS) of yield strength 400 ksi, 500 ksi and 550 ksi with different content of alloying elements Fe, Ni, Co, Mo, W, V are described. The process of vacuum melting of the concerned steels was presented as well as further processing, i.e. homogenizing treatment, hot working, machining, solution treatment, ageing and grinding in order to prepare plates with dimensions of 50 × 50 × 10 mm. The manner of perpendicular firing at the aforementioned plates placed on a stand with RHA armour “witness” plate is presented. Moreover, demonstrated are also the visible results of maraging plates firing with 12,7 mm B-32 type armour-piercing incendiary projectiles on RHA plates. Also shown are the images of scans performed using an electron microscope of maraging plates’ fracture surface generated by firing.

Precipitation, microstructure and mechanical properties of low nickel maraging steel

Abstract: A maraging steel with a composition of Fe–12·94Ni–1·61Al–1·01Mo–0·23Nb (wt-%) was investigated. Optical, scanning electron and transmission electron microscopy and X-ray diffraction analysis were employed to study the microstructure of the steel after different aging periods at temperatures of 450–600°C. Hardness and Charpy impact toughness of the steel were measured. The study of microstructure and mechanical properties showed that nanosized precipitates were formed homogeneously during the aging process, which resulted in high hardness. As the aging time is prolonged, precipitates grow and hardness increases. Fractography of the as forged steel has shown mixed ductile and brittle fracture and has indicated that the steel has good toughness. Relationships among heat treatment, microstructure and mechanical properties are discussed. Further experiments using tensile testing and impact testing for aged steel were carried out.

Corrosion Behavior of 18% Ni M250 Grade Maraging Steel under Weld Aged Condition in Hydrochloric Acid Medium

Abstract: The corrosion behavior of 18% Ni M250 grade maraging steel under weld aged condition has been investigated in hydrochloric acid medium The studies were carried out in hydrochloric acid solutions of different concentrations (01 M – 2 M) at different temperatures (30 0C – 60 0C) by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques The results showed that the corrosion rate increased with the increase in temperature and with the increase in the concentration of hydrochloric acid in the corrosion medium Activation parameters were evaluated using Arrhenius equation and transition state equation The results from the two techniques are in good agreement The surface morphology of the corroded specimen was compared with that of the un-corroded one by using scanning electron microscopy (SEM)

A magnetic method for determining the concentration of residual austenite in maraging steels

Abstract: The results of measurements of magnetic properties of maraging steel 08Kh15N5D2T subjected to different types of thermal treatment, namely annealing, hardening, and aging, are presented. The required concentration of residual austenite during specimen preparation was obtained by varying the temperature of thermal treatment, the time of exposure, and the heating rate in the case of annealing. The new magnetic parameter N*, which linearly correlates with the concentration of residual austenite, is proposed. An algorithm for previously developed equipment and software, which is intended for the determination of this parameter, is offered.

Significance of Alloying Element Levels in Realizing the Specified Tensile Properties in 18 Wt % Nickel Maraging Steel

Abstract: Among the various grades of commercially available 18 wt. % nickel maraging steels, the one with nominal 0.2% proof strength in the range 1700-1750 MPa is the most commonly used and is distinguished by an excellent combination of high strength and high fracture toughness. The main alloying elements are nickel, cobalt, molybdenum and titanium. The first three of these are present at relatively high concentrations in the chemical composition. The high cost of these metals leads to a high cost of production and this becomes a deterrent to extensive use of the steel. In the present study, an attempt was made to produce the steel by pegging the levels of these alloying elements in the lower half of the specified range. The objective was to save on the raw material cost, while still conforming to the specification. The steel so produced could not, however, attain the specified tensile properties after final heat treatment. The observed behavior is explained based on the role played by the different alloying elements in driving the precipitation hardening reaction.

Composite plate and method of forming the same

Abstract: A method of forming a composite plate of maraging steel is disclosed. Formation may comprise depositing a layer comprising a first maraging steel powder onto a surface of a slab comprising a second maraging steel. The first maraging steel may be harder than the second maraging steel. The deposited layer comprising the first maraging steel powder may be hot isostatic pressed onto the slab comprising the second maraging steel to form an intermediate composite slab. The intermediate composite slab may be roll-bonded to form the composite plate. A composite plate of maraging steel formed by this method is also disclosed.