Showing papers on "Maraging steel published in 1994"
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TL;DR: A new type of maraging steel, Sandvik 1RK91, intended for use in surgical applications has recently been developed at Sandvik Steel as discussed by the authors, which showed a remarkably high microstructural stability against overaging, softening being observed only at 580 °C.
Abstract: A new type of maraging steel, Sandvik 1RK91, intended for use in surgical applications has recently been developed at Sandvik Steel, Sandviken, Sweden. In the present article, a comparison was made between this steel and a traditional maraging steel with respect to mechanical and physical properties after tempering treatments in the temperature range 375 °C to 580 °C. The tempering behavior was studied by analyzing hardness, resistivity, and volume fraction of magnetic phase. Sandvik 1RK91 showed a remarkably high microstructural stability against overaging, softening being observed only at 580 °C. In comparison with the reference steel, the hardness of Sandvik 1RK91 was found to be considerably higher in the whole range of temperatures, with the maximum values corresponding to a strength of 3000 MPa for the smallest dimensions of wire. A detailed microstructural investigation of precipitation reactions in Sandvik 1RK91 revealed a new type of precipitate at 475 °C that was found to be of a quasicrystalline nature. These precipitates, which were found to give the major contribution to particle strengthening after tempering at 475 °C, showed a close resemblance to intermetallic trigonalR phase with a chemical composition of about 50 pct molybdenum, 15 pct chromium, 30 pct iron, and 5 pct silicon. The similarity between the quasicrystalline precipitates andR phase was reflected as a second-order transition occurring at about 525 °C. The extremely high strength in 1RK91 can be ascribed to the quasicrystalline nature of the precipitates because of impeded particle shearing.
55 citations
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TL;DR: In this paper, the magnetic properties in annealed and cold rolled conditions have been investigated for maraging steel grade 18%Ni-2400 in order to investigate the structural changes taking place during reversion of austenite.
Abstract: Magnetic properties in annealed and cold rolled conditions have been investigated for maraging steel grade 18%Ni-2400. The austenite content, coercive field, saturation magnetisation and remanence were determined after ageing for 1 h in the temperature range from 400 to 800°C. The results show that the degree of deformation imparted to martensite influences both the amount of reverted austenite and the magnetic properties obtained following ageing. Transmission electron microscopy was carried out in order to investigate the structural changes taking place during reversion of austenite.
28 citations
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TL;DR: In this paper, the effect of the degree and type of deformation imparted to martensite has been investigated in an 18 wt-%Ni 350 grade maraging steel and the validity of X-ray diffraction technique in determining the reverted austenite content is discussed with reference to texture incorporated during cold forming.
Abstract: Austenite reversion as a function of deformation processes has been investigated in an 18 wt-%Ni 350 grade maraging steel. The results reported show that the degree and type of deformation imparted to martensite influences the amount of reverted austenite obtained following aging. The validity of the X-ray diffraction technique in determining the reverted austenite content is discussed with reference to texture incorporated during cold forming. Transmission electron microscopy was carried out to study the partitioning of solute during austenite reversion.MST/1842
26 citations
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TL;DR: In this article, the behavior of maraging steel was studied in these two regions and the diffusion coefficient of species inside the oxide layer was determined, indicating that the corrosion kinetics are not the same.
22 citations
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TL;DR: In this article, the effect of nickel and molybdenum concentrations on the phase transformation and mechanical properties of conventional 18Ni(350) maraging steel has been investigated, and the aging response of these materials has also been investigated using optical, scanning electron, and scanning transmission electron microscopy.
Abstract: The effect of nickel and molybdenum concentrations on the phase transformation and mechanical properties of conventional 18Ni(350) maraging steel has been investigated. Both of these elements act as strong austenite stabilizers. When the concentration of molybdenum or nickel is greater than 7.5 or 24 wt %, respectively, the austenite phase remains stable up to room temperature. In both molybdenum- and nickel-alloyed steels, the austenite phase could be transformed to martensite by either dipping the material in liquid nitrogen or subjecting it to cold working. When 7.5 wt% Mo and 24 wt% Ni were added in combination, however, the austenite phase obtained at room temperature did not transform to martensite when liquid-nitrogen quenched or even when cold rolled to greater than 95% reduction. The aging response of these materials has also been investigated using optical, scanning electron, and scanning transmission electron microscopy.
18 citations
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22 Nov 1994TL;DR: A powder-metallurgy-produced, essentially titanium-free, nickel-containing maraging steel article such as for use in the manufacture of die casting die components and other hot work tooling components is described in this paper.
Abstract: A powder-metallurgy-produced, essentially titanium-free, nickel-containing maraging steel article such as for use in the manufacture of die casting die components and other hot work tooling components. The article preferably contains an intentional addition of niobium. The article may be produced as a hot-isostatically-compacted, solution annealed, fully dense mass of prealloyed particles, or alternately, as a hot-isostatically-compacted, plastically deformed and solution annealed, fully dense mass of prealloyed particles.
12 citations
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TL;DR: In this paper, an ultra-high-strength low-alloy NiSiCrCoMo steel has been developed, with tensile, impact and fracture toughness properties matching those of maraging steel 250 grade in tonnage scale melts.
Abstract: An ultra-high-strength low-alloy NiSiCrCoMo steel has been developed. The development work is part of a major programme at the Defence Metallurgical Research Laboratory in the field of ultra-high-strength, high-fracture-toughness steels. In this context we undertook investigations to understand the effect of solute additions on the fracture behaviour of Armco iron and Fe-C alloys. We investigated Fe-Ni, Fe-Co, Fe-Si, Fe-Mo, Fe-C-Ni and Fe-C-Co alloys for mechanical behaviour. The report by Garrison (1986) on a Fe-C-Ni-Si-Cr alloy was an important pointer to a low-alloy, ultra-high-strength steel with high fracture toughness. The material we have now arrived at is a Fe-C-Ni-Si-Cr-Co-Mo steel with tensile, impact and fracture toughness properties matching those of maraging steel 250 grade in tonnage scale melts.
11 citations
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TL;DR: In this article, the authors reported that the addition of 9%Co to the base alloy plus 2·5%Mo increases the ductile-brittle transition temperature (DBTT) to 120°C in unaged material.
Abstract: The addition of Co to 18%Ni maraging steels produces an increase in hardness due to a synergistic effect. A similar effect is reported in this paper for maraging steels based on Fe–5Mn–6Ni. However, Co is thought to have an effect on the ductile-brittle transition temperature (DBTT) of mar aging steels. The addition of 9%Co to the base alloy plus 2·5%Mo increases the DBTT to 120°C in unaged material. Similar to reports by other workers on Fe–Co alloys, it is considered that this increase in DBTT is due to Co restricting cross-slip. In contrast, Mo is thought to lower the DBTT by increasing cross-slip. The reason for 2·5%Mo changing the mode of brittle fracture from intergranular to transgranular cleavage in the base alloy is discussed. Mention is also made of the effect of Ni on the DBTT in lath martensite structures. In classical 18%Ni maraging steel, the DBTT of the Fe–18Ni base is probably so low that the addition of Co does not seriously embrittle the steel.MST/1828
11 citations
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TL;DR: In this article, the influence of solution treatment temperatures (S.T.) on microstructure, tensile and fracture properties of 18 Ni cobalt free maraging steel is discussed in light of the prevailing microstructural conditions.
Abstract: The study presents the influences of solution treatment temperatures (S.T.T.) on microstructure, tensile and fracture properties of 18 Ni cobalt free maraging steel. The results are thoroughly discussed in light of the prevailing microstructural conditions as revealed by optical and transmission electron microscopy, and detailed scanning electron fractography. It is found that tensile strength in both unaged and aged conditions is independent of solutioning temperature and, consequently, grain size. However, the tensile ductility, CVN and K IC in aged condition get severely affected with the increase in S.T.T. because of a change occurring in the martensitic lath morphology from blocky to stringer type
9 citations
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TL;DR: In this paper, electron-beam high-speed isothermal heating local aging treatment strengthened austenite but not martensite to improve the strength of joints is pointed out, basing on this investigation.
Abstract: Improving the strength of 2401 MPa maraging steel weldments is studied in this investigation. Solidified structures of weld metal are controlled by electron-beam scanning welding so that the strength of weld metal can be increased by 10%. This result is equal to that of aging treatment after welding. Simulating the electron beam isothermal heating process, local aging treatment is done on the joint and the best parameters of heat treatment are attained by means of experiment. The ultimate strength of the joint can reach 96% of the base metal's. The ultimate strength of the joint after electron beam isothermal heating local aging treatment is 93% of the base metal's. This agrees with the result of simulation. The strength of the treated joint is equal to that of solution and aging treatment after welding. The fracture appearance shows small reinforced dimples. The amount of residual austenite increases by 30%. Residual austenite uniformly distributes at the boundaries of cellular dendrites. Ti and Mo are found to segregate at the boundaries and form reinforced phases consisting of Ni and Ti or Ni and Mo, respectively. A new opinion that electron-beam high-speed isothermal heating local aging treatment strengthens austenite but not martensite to improve the strength of joints is pointed out, basing on this investigation.
6 citations
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TL;DR: In this article, the possibility of gainfully utilizing grade 18Ni(350) maraging steel scrap has been investigated, along with the effect of additional alloying with niobium.
Abstract: The possibility of gainfully utilizing grade 18Ni(350) maraging steel scrap has been investigated, along with the effect of additional alloying with niobium. A vacuum induction melting and casting furnace was used for melting and additional alloying. The cast ingots were hot forged and their properties compared with those of the stock material. The composition of the reprocessed material was found to be within the prescribed range for 18Ni(350) steel, except for some loss in titanium content. The hardness and tensile strength of the recycled steel were similar to those of the stock material. A slight decrease in hardness in the aged condition could be attributed to loss of titanium during remelting. Charpy V- notch impact test-ing indicated significantly higher toughness in the remelted material; this has been attributed to a homo-geneous, refined microstructure and a lower level of inclusions. Additional alloying with 2% Nb not only improved the mechanical properties but also affected the amount of reverted austenite obtained after ag-ing.
31 Dec 1994
TL;DR: In this paper, the authors examined the hydrogen embrittlement behavior of cast super duplex stainless steel and cast maraging steel as a function of electrode potential and hydrostatic pressure, i.e., the water depth, in synthetic sea water using fracture mechanics bolt-loaded wedge-opening (WOL) specimens.
Abstract: Hydrogen embrittlement behavior of cast super duplex stainless steel and cast maraging steel was examined as a function of electrode potential and hydrostatic pressure, i.e, the water depth, in synthetic sea water using fracture mechanics bolt-loaded wedge-opening (WOL) specimens. The experimental variables investigated included: (1) Electrode potential: free corrosion potential and cathodic protection; (2) Hydrostatic pressure: ambient and 10 MPa corresponding depth of 1,000 meters. The duplex stainless-,steel was not susceptible to hydrogen embrittlement with initial stress intensity values of 30 MPa{radical}m < K{sub i} < 45 MPa{radical}m at ambient pressure. However, at pressure of 10 MPa slight crack growth was observed at open circuit potential and the crack growth was enhanced by the cathodic protection. The maraging steel was susceptible to hydrogen embrittlement in all tests, with all examined initial stress intensity values, K{sub i} < 36 MPa{radical}m. At the open circuit potential the crack growth rate was almost independent of the pressure. Cathodic protection enhanced crack growth and lowered the threshold stress intensity value at ambient as well as at 10 MPa pressure and the crack growth rate increased clearly as pressure increased from 0.1 MPa to 10 MPa. According to these experimental results the combined effect ofmore » cathodic protection and hydrostatic pressure must be taken into consideration when designing new offshore structures and equipment especially for deep sea application.« less
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TL;DR: An ultra-high strength maraging steel bolt, used to fasten steel bands in an aerospace separation system failed prematurely under a sustained stress of about 42 % of its tensile strength during its qualification tests prior to acceptance for flight as mentioned in this paper.
Abstract: An ultrahigh strength maraging steel bolt, used to fasten maraging steel bands in an aerospace separation system failed prematurely under a sustained stress of about 42 % of its tensile strength during its qualification tests prior to acceptance for flight. The metallographic investigation of this failed bolt revealed that certain defects on its surface were filled up by multipass welding causing an inhomogeneous microstructure as well as the accumulation of hydrogen at its sharp thread roots. This caused the delayed failure of the bolt at a lower stress level
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TL;DR: The effect of a maraging heat treatment on the mechanical properties and corrosion behaviour of a special grade of heat treatable stainless steel has been studied in this paper, where the authors found that the corrosion properties such as strength and hardness of this steel are enhanced after the maraging heating treatment, but its corrosion resistance is reduced as a result of the formation of intermetallic precipitates at the grain boundaries.
Abstract: The effect of a maraging heat treatment on the mechanical properties and corrosion behaviour of a special grade of heat treatable stainless steel has been studied Although the mechanical properties such as strength and hardness of this steel are enhanced after the maraging heat treatment, its corrosion resistance is reduced as a result of the formation of intermetallic precipitates at the grain boundaries In addition, oxide scales are formed on the surface of the specimens after the heat treatment owing to high temperature oxidation and these scales play an important role in the corrosion behaviour of the aged specimens Corrosion studies have been conducted on underaged, peak aged, and overaged specimens with and without oxide scales and on specimens in the solution annealed condition Impedance and potentiostatic anodic polarisation techniques in 3·5%NaCl of pH 1, 4, 7, and 10 at room temperature have been used The corrosion performance order of this maraging steel with oxide scales in acidic
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TL;DR: In this article, the influence of aging treatment on the fatigue strength of 18 Ni-maraging steels has been investigated in relation to the behavior of age hardening and the formation of reversion austenite in an 18Ni-8Co-5Mo steel.
Abstract: The influence of aging treatment on the fatigue strength of 18 Ni-maraging steels has been investigated in relation to the behavior of age hardening and the formation of reversion austenite in an 18Ni-8Co-5Mo steel. In the present study, fatigue test was performed on two series of specimens in order to make the effect of age hardening phases on fatigue property clear; in the first series, the strength of test pieces was controlled to have the same proof strength by varying aging temperature and time, and in the second series, it was changed by varying aging time at 750K, which is usually applied as the aging temperature in the commercial 18Ni-maraging steel. Fractography was also examined to study the fracture mode. The main results obtained are as follows.(1) The fatigue limit is almost independent of the aging condition of specimens as far as they have the same proof strength. The computed fatigue strength, however, decreases when specimens have been hardened through the precipitation of low temperature phases.(2) In the case of 750K aging, specimens strengthened to around the maximum hardness (Hv 450) have the almost same value in the fatigue limit independent of small difference in the aging time, although the fatigue limit of under-aged specimens was much lower.(3) A small amount of reversion austenite, which is formed in an over-aging condition, is very effective in increasing fatigue resistance. An amount of 3 vol% austenite was enough for improving the fatigue limit of a maraging steel used.
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06 Sep 1994
TL;DR: In this paper, the content of Ni and Ti is prescribed to produce maraging steel for a die casting die excellent in softening resistance and toughness by preparing a specified componental compsn.
Abstract: PURPOSE:To produce maraging steel for a die casting die excellent in softening resistance and toughness by preparing maraging steel having a specified componental compsn. in which the content of Ni and Ti is prescribed. CONSTITUTION:Maraging steel contg., by weight, 12 to 14% Ni, 4.5 to 6.0% Mo, 7.5 to 9.5% Co, 0.5 to 1.0% Ti, <=0.03% C, <=0.1% Si, <=0.1% Mn, <=0.01% P, <=0.01% S, <=0.05% Cr, <=0.01% N and 0.02 to 0.20% solAl, and the balance Fe with inevitable impurities is prepd. In this way, the maraging steel for a die casting die high in softening resistance and excellent in toughness can be obtd.
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01 Jan 1994TL;DR: In this article, a single-shot explosive welding technique was used to construct multilayered aluminum and titanium base composites reinforced with 18%Ni maraging steel sheets using finite difference analysis.
Abstract: Multilayered aluminum and titanium base composites reinforced with 18%Ni maraging steel sheets were fabricated using single-shot explosive welding technique. Explosive welding conditions for moderate bonding, such as collision velocity and the kinetic energy loss by each collision of multilayered plates, are calculated using finite difference analysis. The estimated conditions can be achieved regulating stand-off between plates and using the multilayered plates with almost the same mass per unit area. Both aluminum and titanium base composites aged after welding showed high tensile strength compared with the composites aged before welding. The ultimate tensile strength of each composite is discussed based on the rule of mixture.
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TL;DR: In this article, both axial and circumferential cracks were revealed, the circumference starting at drilling marks on the bore of a Bourdon tube, and they were shown to be caused by a hydrogen embrittlement mechanism.
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29 Nov 1994
TL;DR: In this paper, the maraging steel contg. dispersed carbide is sintered and then the body is heated to 650 to 800 deg.C to soften it before the solution heat treatment.
Abstract: PURPOSE:To improve machinablity of the maraging steel contg. dispersed carbide. CONSTITUTION:The maraging steel contg. dispersed carbide is sintered and thereafter the sintered body is heated to 650 to 800 deg.C to soften it before the solution heat treatment. With this softening step, the hardness of the sintered body can be lowered to a value sufficient for performing the machining without adversely affecting the other characteristics. Thereafter the resulting sintered body is subjected to solution heat treatment and age hardening treatment. Thus the maraging steel which contains dispersed carbide and has excellent hardness and superior wear resistance can be produced.
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TL;DR: The authors discusses and reviews the work done at CECRI on the metallurgical aspects of corrosion of some industrially important alloys like steel and aluminium alloy weldments, stainless maraging steel and prestressing steel.
Abstract: Metallurgical properties have strong effects on corrosion. The paper discusses and reviews the work done at CECRI on the metallurgical aspects of corrosion of some industrially important alloys like steel and aluminium alloy weldments, stainless maraging steel and prestressing steel. The corrosion control methods for the above materials are also reviewed.
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TL;DR: In this paper, acoustic emission studies have been carried out on a batch of center cracked M250 maraging steel welded specimens, having crack depth to specimen thickness ratio of 0.11 to 0.17.
Abstract: Acoustic emission studies have been carried out on a batch of center cracked M250 maraging steel welded specimens, having crack depth to specimen thickness ratio of 0.11 to 0.17. Broad-band AE sensors with 100-360 kHz bandpass filter have been employed for the experiments. The studies promise the prediction possibility for the hardware constructed out of this material well before their final future and hence can facilitate generation of suitable acceptance criteria for the evaluation of hardware in real time
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TL;DR: In this paper, the maximum failure load of a compact tension (CT) specimen obtained from the R-curve of the material is used for comparing the failure load for the test coupon.
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01 Jan 1994
TL;DR: In this paper, the surface layers of an 18 wt.% maraging steel were synthesized on specimens of 18.5% steel and they were shown to be hard and metallurgically bonded to the surface.
Abstract: Nitrided surface layers are synthesized on specimens of an 18 wt.% maraging steel. The nitrided layers are hard and are metallurgically bonded to the surface. The strength of the layers is superior if the material is deformed and aged prior to nitriding process. The grains are textured and are finer than the grains in layers on annealed material. Contrary to the layers on annealed material. no cracks are observed in deformed and aged specimens. The layer is predominantly γ′-Fe3N phase.
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TL;DR: In this article, the influence of heat treat cycles on the properties of type 20N1OKhMYu maraging steels with complex hardening as the result of precipitates of carbide and intermetallide phases was investigated.
Abstract: The results are presented of investigation of the influence of heat treat cycles on the properties of type 20N1OKhMYu maraging steels with complex hardening as the result of precipitates of carbide and intermetallide phases.
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07 Jan 1994
TL;DR: In this paper, the procedure consists of making the blade in two sections (10, 12), each of which is drawn, rolled, stamped and machined separately and then joined together.
Abstract: The procedure consists of making the blade in two sections (10, 12), each of which is drawn, rolled, stamped and machined separately and then joined together The two sections are made from materials with different properties, eg a high alloy maraging steel for the tip and a carbon steel for the upper section, and the two are welded together The two sections can be given their thermal treatment prior to assembly, and given their finishing treatment after assembly The tip of the blade can be made with one or more breaking points ADVANTAGE - Greater safety with improved mechanical performance