Showing papers on "Maraging steel published in 1995"
TL;DR: In this paper, the evolution of reverted austenite in 18Ni(350) maraging steel was examined using transmission electron microscopy, and the types of reverted Austenite observed were determined by the aging temperature and time.
77 citations
TL;DR: In this paper, a thorough microstructural investigation has been performed on a high strength maraging steel of the type 12%Cr-9%Ni-4%Mo-2%Cu-1%Ti.
Abstract: A thorough microstructural investigation has been performed on a high strength maraging steel of the type 12%Cr-9%Ni-4%Mo-2%Cu-1%Ti. The major precipitate formed during isothermal aging at 475 C is a quasicrystalline phase possessing icosahedral symmetry termed R{prime}-phase with a typical chemical composition of 48%Mo-33%Fe-13%Cr-2%Ni-4%Si. At 550 C the major precipitate is trigonal R-phase with a typical composition of 45%Mo-31%Fe-18%Cr-4%Ni-2%Si. At 550 C also Laves phase with a composition of 48%Mo-35%Fe-13%Cr-2%Ni-2%Si could be observed. At both 475 and 550 C an ordered phase termed L-phase precipitated. This minority phase has an ordered face centered cubic (f.c.c.) structure of type L1{sub 0}. Its composition is typically 9%Fe-4%Cr-52%Ni-15%Mo.-16%Ti-4%Al. R{prime}-phase formed at 475 C transformed to R-phase and Laves phase during aging at 550 C. In an analogous manner, R-phase and Laves phase formed at 550 C transformed to R{prime}-phase during subsequent aging at 475 C. This transformation was rationalized by a strong similarity in crystal structure between quasicrystalline R{prime}-phase of icosahedral symmetry and Frank-Kasper phases such as R-phase and Laves phase.
74 citations
TL;DR: In this article, the authors investigated the mechanism of reversion of martensite to stable austenite in 18Ni-8Co-5Mo type maraging steels.
Abstract: The mechanism of austenite reversion in 18 Ni Co-free maraging steel (250 grade) has been established by conducting extensive X-ray diffraction (XRD) and transmission electron microscopy (TEM) under differently aged conditions. It has been proposed that contrary to the precipitate dissolution mechanism suggested for the initiation of austenite reversion in 18Ni-8Co-5Mo type maraging steels, the initiation of transformation of martensite to austenite in this type of maraging steel is due to the diffusion of Ni from matrix to the dislocations and other defect structures on prolonged/high temperature ageing. This results in local enrichment of Ni which lowers both A s and M s temperatures of the region. Lowering of these transformation temperatures is responsible for the early reversion of martensite to Ni-enriched stable austenite which, on subsequent cooling to room temperature, does not transform back to martensite.
50 citations
TL;DR: In this paper, the nature of the martensite, which provides the basis for the maraging treatment, has been investigated in a maraging steel 1RK91, the nose temperature being about {minus}40 C.
Abstract: The present paper is concerned with the nature of the martensite, which provides the basis for the maraging treatment Rather than forming martensite during cooling, 1RK91 develops martensite when held at a constant temperature in a range from room temperature and below Isothermal martensite formation showing C-curve kinetics was found to occur in the maraging steel 1RK91, the nose temperature being about {minus}40 C The kinetics was found to be enhanced for higher austenitizing treatment temperatures, presumably through a combination of larger grain size and a larger number of quenched in nuclei for isothermal martensite transformation Experiments involving different cooling rates showed that fast cooling enhanced the transformation kinetics Based on this observation it is suggested that quenched-in vacancy clusters provide suitable strain embryos for isothermal martensite nucleation
32 citations
TL;DR: In this article, an experimental program of wire drawing using different lubricants and dies at temperatures varying from ambient to 800°C was described, where soap, colloidal graphite, polyethylene and low melting point glass were tested as lubricants.
20 citations
TL;DR: The aging behavior of 18Ni(350) maraging steel was studied by Mossbauer spectroscopy as discussed by the authors, where the aging reactions start with the redistribution of atoms, which results in the formation of Fe-Co-rich zones and Ni-Mo-Ti-rich regions at the early stages of aging.
15 citations
TL;DR: In this article, the magnetic properties of maraging steels have been investigated as a function of nickel concentration, which varied from 12 to 24 wt pct, while other alloying constituents were kept at a level maintained in the 18Ni-2400 MPA grade maraging steel.
Abstract: Magnetic properties of maraging steels have been investigated as a function of nickel concentration. The alloys nickel content varied from 12 to 24 wt pct, while other alloying constituents were kept at a level maintained in the 18Ni-2400 MPA-grade maraging steel. The magnetic properties were determined following aging for 1 hour in the temperature range of 450 °C to 750 °C. In every alloy investigated, the coercive field increased with aging temper-ature, reaching a maximum around 670 °C ± 30 °C. The saturation magnetization values were lowest around temperatures where maximum coercive field was observed. The coercive field increased from ∼55 to ∼ 175 Oe (∼4380 to ∼ 13,900 amp/meter) and the corresponding sat-uration magnetization decreased from ∼18,500 to ∼ 4000 G (∼1.85 to ∼0.4 T) in the alloys containing 12 and 24 wt pct Ni, respectively. The reverted austenite increased from 25 vol pct at 12 wt pct Ni to 100 vol pct at 24 wt pct Ni. The hardness and Charpy impact strength of the alloys have also been determined. An attempt has been made to correlate magnetic properties with different phase transformations occurring in maraging steels.
11 citations
TL;DR: In this article, the role of chromium in the mechanical properties of Fe-5Mn-9Ni-5Mo-1.5Ti maraging steels containing up to 3% chromium was investigated.
Abstract: This experiment investigated the role of chromium in the mechanical properties of Fe-5Mn-9Ni-5Mo-1.5Ti maraging steels containing up to 3% chromium. Remarkable age-hardening responses were observed in the Fe-5Mn-9Ni-5Mo-1.5Ti and Cr-bcaring alloys. A ductile-brittle-ductile transition occurred in the Cr-bearing alloys during isothermal aging below 510°C. This was due to the segregation of titanium and manganese to prior austenite grain boundaries and their subsequent desegregation into the matrix. The addition of chromium to the base alloy considerably improved its ductility after aging at 520°C. From microstructure and AES analyses, it is suggested that chromium addition augments the volume fractions of (Fe,Mn)2Mo and η-Ni3Ti precipitates in the Fe-5Mn-9Ni-5Mo-Cr alloys, which act as sinks of manganese and titanium in the matrices. This resulted in the reduction of the alloying elements concentration in the matrix, which is followed by the reduction in the segregation level of the elements at prior austenite grain boundaries, and consequently enhanced intergranular fracture strength. The optimum combination of strength and ductility was obtained in the Fe-5Mn-9Ni-5Mo-3Cr-l.5Ti alloy aged at 520°C for 2 hr. and was σ0 2=1721 MPa, σLS=1756 MPa. and e,= 10.2%.
10 citations
TL;DR: In this article, an ultra-high strength NiSiCrCoMo low-alloy steel has been developed, supported by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture resistance of iron, with and without the presence of carbon.
Abstract: Ultrahigh strength steels have been used increasingly in recent years for critical aircraft and aerospace structural applications. In such applications, though materials performance is of prime consideration, cost and availability makes the low-alloy steels an attractive option. This paper describes the development of an ultrahigh strength NiSiCrCoMo low-alloy steel, supported by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture resistance of iron, with and without the presence of carbon. The results of the basic studies, in combination with the work of Garrison (1986) on a NiSiCr steel, have profitably been employed in the development of a NiSiCrCoMo low-alloy steel possessing a strength-toughness combination quite comparable to the highly alloyed 250-grade maraging steel. Reproducibility of attractive strength and toughness properties has been established in tonnage scale melts. This steel, in the softened condition, has good formability and machinability. Weld parameters have also been established. The NiSiCrCoMo low-alloy steel thus meets the requirements of performance and cost rendering it an attractive option for advanced structural applications.
9 citations
Dissertation•
01 Jan 1995
TL;DR: In this article, a study of the dynamic mechanical properties of two types of carbon fiber composite: IM7/977-2 with 977 2 toughened thermoplastic PEEK resin, and IM 7/APC2 with thermoplastically PEEK resins with a volume fraction of 62%.
Abstract: This thesis describes a study of the dynamic mechanical properties of two
types of carbon fibre composite: IM7/977-2 with 977-2 toughened
thermoset resin, and IM7/APC2 with thermoplastic PEEK resin, both using
Hercules IM7 carbon fibres with a volume fraction of 62%. The Split
Hopkinson Pressure Bar (SHPB) is used to produce dynamic strain rates
ranging from 103 to 5xl03 s-', while Instron and Hounsfield screw driven ·
machines are used to give a constant strain rate of about 2 x 10-3s-1 for
comparative quasi-static loading.
The Split Hopkinson Pressure Bar (SHPB) technique uses specimens in
the form of a cylinder, sandwiched between two maraging steel bars. One
of the maraging steel bars is subjected to an impact produced by a
projectile. The Instron and Hounsfield machine used the same form of
specimen. A strain gauge method has also been used to record the strain
directly by attaching a strain gauge on to the specimen under test.
Three different fibre orientations have been investigated: unidirectional
fibre with loading parallel (0°) to the axis of the specimen; transverse
loading (90°) where the fibres are perpendicular to the axis of specimen;
and quasi-isotropic with transverse loading .
The dynamic stress-strain properties of the carbon fib~e composites have
been investigated experimentally at room temperature under quasistatic
condition and at the high strain rates produced in the SHPB method using
loading pulses of about 100 μS duration and rise time of 12 μS. The effects
of strain rate on stiffness, yield stress and strength for the composites
have been determined and compared with those obtained from a
mathematical model (Rule of Mixtures).
The longitudinal carbon fibre composite had the highest stiffness, followed
by the quasi-isotropic composite, and then the transverse composite. For compressive strength, the quasi-isotropic had the highest strength followed
by the longitudinal and then the transverse. The fracture energy has also
been obtained indicating that for the quasi-isotropic composites, IM7/977-2
has a considerably high fracture energy than IM7/APC2. The bulk
temperature rise has also been predicted up to the fracture stress.
9 citations
TL;DR: In this paper, a computer-simulated electron diffraction analysis was applied to determine the nature of the strengthening precipitates in 18Ni(350) maraging steel and the results showed that the strengthening is caused by a refined distribution of the rod-shaped Ni3Mo and η-Ni3Ti precipitates.
TL;DR: In this article, the influence of reversion austenite on the fatigue behavior of a maraging steel has been investigated by using 18%Ni-8%Co-5%Mo steel.
Abstract: The influence of reversion austenite on the fatigue behavior of a maraging steel has been investigated by using 18%Ni-8%Co-5%Mo steel. The behaviors of age hardening and reversion from martensite to austenite were examined first under various aging conditions in the temperature range of 750-850K. These aging conditions were chosen so that a selected volume fraction of austenite (γvol%=1, 2, 3 or 24%) was formed in the age hardened maraging steel. The specimens were subjected to fatigue test, crack growth test and fractography. The results obtained are as follows:(1) The formation of reversion austenite results in a great improvement of fatigue strength. Especially, a small amount of austenite (2-3vol%) markedly increases the fatigue limit of a maraging steel without reducing the hardness so much. Due to the existence of reversion austenite, crack growth tends to be suppressed and the maximum length of non-propagating crack becomes longer.(2) The existence of reversion austenite improves the fatigue fracture toughness.
Journal Article•
TL;DR: In this article, an N18K9M5T maraging steel was used as a semihard magnet for the disk rotors of highspeed hysteresis electric motors.
Abstract: When subjected to thermomechanical treatment, which includes cold straining and high-temperature annealing with the precipitation of an intermetallic Ni 3 Ti phase and thin-plate γ martensite, an N18K9M5T maraging steel changes to an anisotropic magnetic state. In this state (B r = 0.96 T, H c = 24 A/cm, B z /B m = 0.80, 0.2 = 1700 MPa, and ψ = 39%), the material can be used as a semihard magnet for the disk rotors of highspeed hysteresis electric motors.
TL;DR: In this paper, the authors studied the environmental cracking of two high-strength steels (250 maraging steel and AISI 4130) under sustained load conditions and found that they were more susceptible to cracking at the same fraction of the corresponding yield strength (the critical flaw was smaller by a factor of five).
TL;DR: In this paper, the characteristics of debinding, sintering and aging behavior were studied for injection molded maraging steel compacts, and also the mechanical properties were investigated by tensile and impact test.
Abstract: The unique combinations of high toughness and high strength available with the maraging steels have made them desirable for structural applications. However, it was very difficult to produce the high performance maraging steels by conventional powder metallurgy (P/M) processes because of hard material. Metal Injection Molding (MIM) process alleviates the need for secondary working operations because of providing the net shape components, which is a suitable production route for hard materials. In this paper, the characteristics of debinding, sintering and aging behavior were studied for injection molded maraging steel compacts, and also the mechanical properties were investigated by tensile and impact test. The results are summarized as follows:1) By using the continuous process which went on through thermal debinding and sintering at 1623K for 3.6ks in hydrogen atmosphere, the compacts were considerably densified to a relative density of 96%.2) Aging hardness at 758K for 10.8ks reached to HRC46.5 which was as hard as the densified steels by HIP, and this aging condition was lower temperature and shorter time as compared to the condition of conventional P/M process.3) Optimum aged MIM maraging steel showed the same strength of 1640MPa as the wrought steels, but the ductility and toughness were considerably poor.
TL;DR: The magnetic properties of the austenite phases were typical of a very weak magnetic material and the coercive field and saturation magnetization values were in the range 1034-2387 Am−1 and 1.6-2.9 T, respectively as mentioned in this paper.
Abstract: Austenitic alloys have been produced by additional alloying in maraging steel grade 18 Ni at 2400 MPa. The concentration of Mo, Ni and Co was increased individually until the martensite start temperature Ms, was suppressed below ambient value. Charpy impact strength, tensile strength and magnetic properties were determined. The impact strength in the annealed condition ranged between 260 to 294 J. In alloys where martensitic transformation occurred following quenching in liquid nitrogen, the impact strength dropped appreciably and was found to be in the range 120–216 J. The tensile strengths of the austenite and martensite phases ranged between 680 to 890 and 1030 to 1100 MPa, respectively. It was observed that the austenite phase transformed to martensite in the region that under went plastic deformation during Charpy and tensile testing. The degree of transformation incorporated, varied as a function of composition. The magnetic properties of the austenite phases were typical of a very weak magnetic material. The coercive field and saturation magnetization values were in the range 1034–2387 Am−1 and 1.6–2.9 T, respectively. In contrast to the general observation, the austenite phase containing high Co exhibited ferromagnetic behaviour. The coercive field and saturation magnetization of ferromagnetic austenite was 1034 Am−1 and 11 T, respectively.
Journal Article•
TL;DR: In this article, the dynamic behavior of three materials (M200 maraging steel, C1008 steel, and 6061-T6 aluminum) at low temperatures and at a strain rate of about 10 3 s −1 is investigated using split-Hopkinson bar (SHB).
Abstract: The dynamic behavior of three materials : M200 maraging steel, C1008 steel, and 6061-T6 aluminum, at low temperatures and at a strain rate of about 10 3 s ―1 is investigated using split-Hopkinson bar (SHB). The tests were conducted at six temperatures between 293 K and 123 K. Vapors from liquid nitrogen around the specimen were used to cool the specimen to the desired temperature. The results for all the three materials show an increase in flow stress at low temperatures. The flow stress of M200 increased to 1.93 GPa at 123 K, an increase of 22 percent, compared to 1.58 GPa at room temperature. In the case of 6061-T6 aluminum, the flow stress remains at about 390 MPa at temperatures in the range 293 to 123 K. For C1008 steel, the flow stress increased to 860 MPa at 123 K from its room temperature value of 610 MPa. The failure strain for C1008 steel at 123 K was 0.02, compared to 0.2 at room temperature. The fractographs of failed C1008 specimens at 198 K suggest a ductile (shear failure) and at 123 K a brittle (transgranular) failure.
Journal Article•
TL;DR: In this paper, acoustic emission studies have been carried out on a batch of welded and center cracked specimens made of 18% Ni M250 maraging steel where the crack depth to specimen thickness ratio varied from approximately 10/80 to 25/80.
Abstract: Acoustic emission studies have been carried out on a batch of welded and center cracked specimens made of 18% Ni M250 maraging steel where the crack depth to specimen thickness ratio varied from approximately 10/80 to 25/80. Broad band AE transducers providing maximum sensitivity in frequency range 135 to 310 KHz were used for the AE monitoring. The paper brings out the AE performance of the specimens with inserted surface cracks of different sizes when the latter become critically severe leading to failure. The studies indicate the prediction possibility for the hardware constructed out of this material reasonably well before their final rupture. The AE signatures are also presented in a form that would facilitate generation of an acceptance criteria for the evaluation of hardware in real time.
Patent•
19 Sep 1995
TL;DR: In this article, the authors proposed a maraging steel excellent in heat check resistance by specifying a composition consisting of C, Si, Mn, P, S, Ni, Cr, Mo, Co, Ti, Al, B, Zr, Ca, and Fe.
Abstract: PURPOSE:To obtain a maraging steel excellent in heat check resistance by specifying a composition consisting of C, Si, Mn, P, S, Ni, Cr, Mo, Co, Ti, Al, B, Zr, Ca, and Fe. CONSTITUTION:This steel is a maraging steel excellent in heat check resistance, having a composition consisting of, by weight, <=0.03% C, <=0.10% Si, <=0.10% Mn, <=0.010% P, <=0.010% S, 6.0-11.0% Ni, <=0.30% or 8.1-9.0% Cr, 4.0-9.0% Mo, 7.0-11.0% Co, 0.10-1.0% Ti, 0.05-0.15% Al, <=0.010% B, <=0.10% Zr, <=0.10% Ca, and the balance essentially Fe. This steel can, be hardened with reduced strain by performing aging treatment at a relatively low temp. of about 500 deg.C.
01 Jan 1995
TL;DR: In this paper, the microstructure and mechanical properties of several alloys (including Ni3Al-base alloys and high speed steels) and particulate reinforced metal matrix composites (MMCs) have been evaluated.
Abstract: In this paper, the recent research activities in the field of spray forming performed at University of Science and Technology Beijing have been briefly reviewed. We have established a spray forming facility recently, and the microstructure and mechanical properties of several alloys (including Ni3Al-base alloys and high speed steels) and particulate reinforced metal matrix composites (MMCs) (including aluminium alloy 2618+SiCp and maraging steel+A12O3) have been evaluated. The results of characterization of the microstructure and mechanical properties of the representing spray deposited materials (Ni3Al-base alloys and Al 2618+SiCp MMC) are given here.
Journal Article•
TL;DR: In this article, the aging process of 18Ni maraging steel has been studied by means of small angle X-ray scattering, Mossbauer spectroscopy and TEM.
Abstract: The aging process of 18Ni maraging steel have been studied by means of small angle X-ray scattering,Mossbauer spectroscopy and TEM.The spinodal decomposition firstly appears at the early stages of 500℃ aging in 18Ni maraging steel after solution treatment,and then the Ni3(Mo.Ti)intermetallic particles containing Fe precipitate in Ni-Mo-Ti rich regions of the modulated structure by in situ nucleation. With increasing aging time,Ni3Mo and Ni3Ti particles coalesce significantly and may be partly resolved into the matrix, and simultaneously the Fe2Mo particles precipitate and the reversed austenite can be found.
TL;DR: In this article, the effect of different kinds and regimes of softening heat treatment not only on the mechanical properties and the structure of the steel but also on its deformation behavior and sensitivity in the stress state is investigated.
Abstract: It has been shown in many investigations that the corrosion-resistant maraging steel 03Kh1 IN I0M2T (BHC 17) has high plasticity and the lowest deformation resistance after softening heat treatment (annealing, quenching, or aging at 650°C). However, the available data are insufficient for the development of a technology for producing parts by cold plastic deformation. In this case it is important to know the effect of different kinds and regimes of softening heat treatment not only on the mechanical properties and the structure of the steel but also on its deformation behavior and sensitivity in the stress state. The sensitivity to dynamic loads is very important. The present work is devoted to the investigation of these problems.
Patent•
19 Sep 1995
TL;DR: In this article, a maraging steel with high temp. strength and excellent heat check resistance was obtained by specifying respective contents of Ni, Co, Mo, Ti, Al, C, Si, Mn, P, S, Cr, and N.
Abstract: PURPOSE:To obtain a maraging steel increased in high temp. strength and excellent in heat check resistance by specifying respective contents of Ni, Co, Mo, Ti, Al, C, Si, Mn, P, S, Cr, and N. CONSTITUTION:This steel is a maraging steel having a composition which consists of, by weight, 8- =675 and 111 which the amounts of C, Si, Mn, P, S, Cr, and N as the impurities are limited to <=0.03%, <=0.1%, <=0.1%, <=0.01%, <=0.01%, <=0.1%, and <=0.01%, respectively. In this maraging steel, high temp. strength is improved while maintaining the superior balance between strength and toughness and also heat check resistance is improved.
13 Aug 1995