Showing papers on "Maraging steel published in 1971"

The strength and fracture toughness of 18 Ni (350) maraging steel

Abstract: The influence of microstructure on the strength and fracture toughness of 18 Ni (350) maraging steel was examined. Changes in microstructure were followed by X-ray and neutron diffraction and by optical and electron microscopy. These observations have been correlated with the fracture morphology established by scanning electron microscopy. Air cooling this alloy from the austenitizing temperature results in a dislocated martensite. During the initial stage of age hardening, molybdenum atoms tend to cluster (forming preprecipitates) and the cobalt assumes short range ordered positions. Subsequent aging results in Ni3Mo and σ-FeTi with overaging being associated with the formation of equilibrium reverted austenite and Fe2Mo. The fracture behavior is examined in terms of elementary dislocation precipitate interactions. It is suggested that the development of coplanar slip in the underaged conditions leads to its increased stress corrosion susceptibility and decreased fracture toughness. The optimum aged condition is then associated with cross-slip deformation. The fracture behavior of the overaged condition is a dynamic balance between a brittle matrix and the ductile (crack blunting) reverted austenite.

Thermal embrittlement of 18 Ni(350) maraging steel

Abstract: The embrittlement of as-solutionized 18 Ni(350) Maraging steel was monitored as a function of heat treatment variables by means of Charpy impact tests The processing parameters of interest were annealing temperatures in the range of 1900° to 2400°F, intermediate holding temperatures in the range of 1300° to 1800°F, and the quenching rate The changes in fracture mode with heat treatment were characterized by replica and scanning electron microscopy The severity of thermal embrittlement increases with decreasing cooling rate from the annealing treatment upon direct quenching to room temperature Intermediate isothermal holding, particularly at 1500° to 1600°F, further accentuates the embrittlement A large grain size is beneficial to the toughness when rapid direct quenches from the annealing range are imposed but is detrimental upon air cooling or intermediate holding The major loss in toughness may be associated with the diffusion of interstitial impurity atoms (C+N) to the austenite grain boundaries during cooling or intermediate isothermal holding below 2000°F An advanced stage of the embrittlement is characterized by the discrete precipitation of Ti(C,N) platelets on these boundaries Thermal embrittlement is accompanied by change in fracture mode from transgranular dimpled rupture to intergranular quasi-cleavage

Mechanisms of corrosion fatigue below K Iscc

Abstract: Information on corrosion-fatigue crack growth in engineering structures is necessary for the prediction of service lives of structures subjected to both fatigue loading and an aggressive environment. The rate of crack growth in corrosion fatigue is governed by the interaction between the chemical mechanisms and the mechanical mechanisms occurring at the crack tip. Thus, as part of a long-range program aimed at establishing the necessary relations for predicting the corrosion-fatigue behavior of structural steels, the crack-tip mechanisms in corrosion fatigue were studied by using controlled-potential techniques, pH measurements at the crack tip, and fractographic analysis of the crack surface. The tests were conducted on 12Ni-5Cr-3Mo maraging steel at a cyclic-stress frequency equal to 6 cycles per minute in a room-temperature pH 7, 3 percent solution of sodium chloride.

Effect of Various Modes of Loading on the Stress Corrosion Cracking of a Maraging Steel

Abstract: An 18Ni (280) maraging steel has been tested in 3.5% NaCl solution under various modes of loading. The most severe condition was plane strain loading of fatigue precracked samples. The severity of stress corrosion cracking (SCC) of unnotched samples decreased in the sequence: plane strain bending, tension, plane stress bending, and torsion. The most consistent explanation for the various observations is that SCC results from hydrogen embrittlement. Under certain circumstances anodic dissolution processes can result in beneficial crack blunting effects rather than SCC failure.

Stress Corrosion Cracking in 18% Ni (250) Maraging Steel

Abstract: The susceptibility of 18% Ni (250) maraging steel to stress corrosion cracking in 3.5% NaCl solution has been investigated. Metallographic and fractographic examinations show distinct diff...

Fracture toughness and stress corrosion characteristics of a high strength maraging steel

Abstract: The effect of heat treatment on the tensile, fracture toughness, and stress corrosion properties of a high strength maraging steel (nominal composition 16.3 Ni−12.87 Co−4.98 Mo−0.78 Ti) is described. A maximum ultimate tensile strength of 323 ksi, combined with a fracture toughnessK Ic of 62 ksi $$\sqrt {in} $$ , was achieved. This strength level appears to be the maximum which can be achieved in maraging type steels without decreasing the crack tolerance below that of currently used high strength low alloy steels. Reversion to austenite did not improve either the fracture toughness or stress corrosion resistance relative to completely martensitic microstructures with equivalent strength.

Surface preparation of maraging steel for electroplating

Abstract: AN IMPROVED METHOD OF PREPARING MARAGING STEELS FOR SUBSEQUENT METAL DEPOSITION BY UTILIZATION OF A COMBINED NITRIC ACID PICKEL-MECHANICAL ABRASION DESCALING STEP IN CONJUNCTION WITH A LOW CURRENT DENSITY ACIDIC ELECTROPOLISHING STEP TO PRODUCE A SCALE FREE, ACTIVATED SURFACE FOR DEPOSITION OF A VERY ADHERENT ELECTRODEPOSIT.

Soft magnetic structural alloys for elevated-temperature applications

Abstract: Metallurgical efforts to develop a soft magnetic material suitable for application in the rotor of a generator or motor in advanced aerospace electric systems are reviewed. Commercial materials which have been considered include AISI 4340 steel, H-11 steel, Nivco alloy, and 15- and 18-percent Ni maraging steels. Developments described have led to several new materials with combination of good mechanical and magnetic properties at elevated temperature. Such materials include an improved maraging steel a precipitation hardenable cobalt-base alloy, a carbide strengthened Co-W alloy, dispersion-strengthened soft magnetic alloys, and unidirectionally solidified Co-Nb-Fe eutectic alloys.

Stress Corrosion Cracking Behavior of Maraging Steel Composites

Abstract: Laminated plate composites were prepared by hot roll bonding together plates of 18Ni(280) maraging steel and sheets of Armco iron. Composite welds of the same geometry were also prepared by successively depositing weld layers of these two materials. Plane strain stress corrosion tests of these two types of composites in aerated 3.5% NaCl solutions showed that stress corrosion crack propagation was stopped at stress intensities well above the KISCC values of the corresponding homogeneous maraging steel base plate and maraging steel weld metal. The results demonstrate that it is possible to retard stress corrosion crack propagation significantly in both base plate and weld structures by the use of a composite approach.

A New Approach for the Production of Maraging Steel P/M Parts

Abstract: The manufacture of maraging steel P/M parts is of interest for a number of reasons. Primarily, there are numerous potential applications for this high strength-high toughness type of material involving parts that could be most economically made by P/M techniques. With the 300,000 to 400,000 psi tensile strength range of certain wrought maraging steels, it is quite conceivable that a P/M material could be made with a strength in excess of 200,000 psi and with substantial ductility, using conventional press and sinter techniques.

Fracture Toughness of Duplex Structures: Part II — Laminates in the Divider Orientation

Abstract: Laminates containing 25 percent of tough (unaged) maraging steel plates and 75 percent of brittle (aged) maraging steel plates were prepared by a special diffusion bonding and heat treating technqiues so that the thickness of the tough constituent was either 0.02, 0.04, 0.06, or 0.08 in. Compact tension fracture toughness specimens were machined so that the laminates were parallel to the sides of the specimens. They were then fractured according to the recommendations of the ASTM and the following three indices of toughness were measured: (1) the plane-strain fracture toughness according to the ASTM recommendations; (2) the fracture toughness based on the maximum load and the initial crack length; and (3) the fracture toughness based on the maximum load and the instantaneous crack length. Four tests were performed at each thickness of the tough constituent; two each at crack lengths of approximately 0.30 and 0.55 in. The plane-strain fracture toughness of the laminates was slightly higher than the plane-strain fracture toughness of the monolithic brittle constituent and was independent of either crack length or the dimensions of the tough constituent. Regardless of the thicknesses of the tough phase the composite toughness was highest for specimens containing cracks 0.30 in. long when the toughness was measured in terms of the other two indicates of fracture toughness. The toughness as a function of thickness exhibited a relative maximum when the tough phase was 0.04 in. thick and a relative minimum when the tough phase was 0.06 in. thick for both the 0.30 and 0.55-in. crack lengths. The experimental results are in broad agreement was a proposed model for crack extension in the divider orientation. /Author/

The effect of reactive metal additions on grain boundary embrittlement in 18Ni200 maraging steel

Abstract: Maraging steel can be embrittled by slowly cooling between 1850° and 1400°F from elevated temperatures (>2200°F) The object of this work was to examine the effect of various refining and hardening additions on the slow cooling embrittlement response of 18Ni200 maraging steel Small refining additions of magnesium give a partial but significant reduction of embrittlement that is caused by grain boundary precipitates Ca, B, and Zr did not have this beneficial effect Of the hardening elements studied, only titanium could be associated with the embrittlement Titanium was otherwise the best hardening addition, judged from its combined effect on the yield strength and toughness of normally annealed plus aged material

Nitriding of maraging steel N18K9M5T

Abstract: 1. Nitriding of maraging steel N18K9M5T results in the formation of a case that is not brittle and is firmly bonded to the base metal, with a depth of 0.2–0.25 mm and a high surface hardness (up to HV 900). 2. Nitriding greatly increases the wear resistance of the steel and also the fatigue limit. 3. After aging and nitriding, steel N18K9M5T has a high corrosion resistance in artificial sea water. 4. To obtain a diffusion layer of sufficient depth with a high surface hardness, nitriding should be conducted in ammonia at 450° for 48 h and at 500° for 24h. In this case nitriding is combined with the aging process.

Heat treatment of large forged and pressed bars of steel 00N18K9M5T

Abstract: The main reasons for the low plasticity and ductility of maraging steel 00N18K9M5T in large sections are the coarse-grained structure resulting from heating for hot working and the precipitation of carbides or titanium carbonitrides in the form of a network in the grain boundaries.

The Evaluation of Glasses As Forging Lubricants

Abstract: : The ring compression test was successfully used to determine the relative efficiency of a number of lubrication systems for the high temperature forging of Type 300A maraging steel and titanium -6 aluminum -4 vanadium alloy. The results clearly indicate the advantage of using both a glass coating on the workpiece and a grease-base lubricant on the tooling. Data obtained has identified the optimum temperature range for use of each of the three glass coatings evaluated. Inaccuracies in the application of theoretical analysis to practical ring test results, due to bulging occurring at high friction levels, can be minimized by using specimens of small ratios of internal diameter and thickness to external diameter. When such precautions are taken, the method of analysis used in this work allows a value for the interface shear of the lubricant system to be determined. Under thick film lubrication conditions, this value would be independent of the flow stress of the workpiece material.

Structure and Property Control through Rapid Quenching of Liquid Metals

Abstract: : The report presents the results and accomplishments of the first year of a three year research program investigating the production of solid bars from rapidly quenched liquid metals. Steam atomization was used to prepare coarse metal powders of a maraging steel VM 300, a nickel base alloy IN100 and cobalt base alloys. This atomization process can be used successfully with cobalt base alloys but does not appear to be suitable for the nickel base alloys. Improvments will have to be made to control the chemistry and the purity of the maraging steel coarse powders produced by steam atomization. Billets and solid bars were produced by hot isostatic compaction, or by extrusion of coarse powders. The bond strength between metal powder particles prior to cold or hot working of the compacted bars is strongly dependent upon the presence of impurities such as oxygen, hydrogen and carbon. Hot isostatic compaction followed by extrusion gave the best results in terms of mechanical properties and homogeneity of the billets. The influence of cooling environments and cooling rates on the secondary dendrite arm spacing and the extent of microsegregation within the coarse powder particles was studied in detail. The mechanical properties and the microstructures of the different alloys produced by the powder process are reported and compared to the properties of the commercially cast and wrought alloys having the same chemistry.

Aluminium-steel composite materials

Abstract: 1,235,973. Welding by rolling or pressing. COMPAGNIE PECHINEY. 21 Aug., 1969 [22 Aug., 1968], No. 41836/69. Heading B3R. A composite material comprising a matrix of aluminium or aluminium alloy a reinforced by parallel layers of steel strips b is formed by rolling or pressing. The width of the steel strips is from 30 to 200 times their thickness, which is from 0A05 mm. to 0A15 mm. The steel is preferably a stainless steel, a martensite steel, a maraging steel, or a steel having a good cold working capacity. The aluminium alloy is preferably an alloy of the Al-Si type, or a hardenable alloy of the Al-Zn-Mg, or Al-Cu-Mg, Al-Mg-Si or Al-Zn-Mg-Cu, type. The ratio of volume between the steel and matrix is from 10 to 50%. The steel strips are preferably encased in aluminium or aluminium alloy prior to rolling or pressing and may be placed with the axes of the strips in one layer parallel to, or across the axes of the adjacent layer.

Method for retarding the decomposition of hydrazine rocket fuels in contact with maraging steels

Abstract: Liquid hydrazine fuel is stored in a maraging steel container, wherein the surface exposed to the liquid fuel comprises a bimetallic couple of metallic cadmium and bare maraging steel. The rate of decomposition of the hydrazine fuel based on the exposed area of maraging steel is markedly lower than that for maraging steel alone.

Co-Mo and Co-Mo-Ti stainless maraging steels

Abstract: 1. Maraging 13Cr−7Ni steels alloyed with 6–7% Co and 3.5–4% Mo have good ductility and low crack sensitivity at a strength of 150–160 kg/mm2. 2. The use of titanium for additional strengthening of Co−Mo steels induces sharp embrittlement of the steel, even with 0.4% Ti.