[en] A study was made on the effect of silicon content (0.08...0.93%) on mechanical properties of maraging N18K9M5T steel in quenched and aged states. It was shown that ductility and impact strength of aged N18K9M5T steel, containing above 0.2% Si decrease due to negative effect of this element on ductility and impact strength of the steel in quenched state. When titanium content is increased above approximately 1.0% the residual austenite is observed in quenched N18K9M5T steel; the austenite doesn't decompose during aging, which results in decrease of hardening efficiency

[en] Maraging steels are materials with very low contents of C and with Ni, Co, Mo and T1 additions, that can reach very high mechanical strength values by combinations of heat treatment operations. Three 18% Ni Maraging steels have had some aspects of their aging kinetics investigated by experimental procedures using electrical resistivity, internal friction and hardness measurement techniques, in samples aged from 30 seconds to several hours. Finally, it was verified that the techniques employed were very adequate to the purposes of the present kinetics studies. (author)

[en] The early stages of aging at 773 K in 18Ni(350) maraging steel were studied by Moessbauer spectroscopy. The experimental results showed that Fe-Co rich zones and Ni-Mo-Ti zones formed at the early stages of aging. The redistribution of atoms is fast at the initial stages of aging and then slows down. Intermetallic compounds were found to precipitate on the Ni-Mo-Ti zones. (orig.)

[en] Structure, mechanical properties and corrosion behaviour of maraging steel type 06Kh13N7D2 are studied depending on heat treatment conditions. The steel is considered as a substituent for chromium steel 20Kh13 and high-nickel steel type 10Kh11N20T3R and KhN35VTYu alloy, which are usually used for load-bearing components in nuclear reactors. The 06Kh13N7D2 steel is shown to possess high corrosion resistance in water and steam-and-water environments and high resistance to corrosion fatigue in chloride-containing media. Irradiation with 10²⁰ cm^-2 neutron fluence does not induce radiation embritlement. The steel is technologically efficient, it has high ductility and weldability. 4 refs.; 4 figs.; 1 tab

[en] Fatigue crack growth tests were carried out using CT specimen under the conditions of stress ratio R=0.1, 0.3, 0.5 for imported maraging steel(VAR), domestic maraging steel(ESR) and AISI4337-V steel. The near-threshold values, stable crack growth chracteristics and the behavior of crack closure were investigated. In the region of near-threshold fatigue crack growth, ΔKth decrease sharply from stress ratio R=0.1 to R=0.3 gradually over stress ratio R=0.3. Constant m increase and constants C decrease under increasing stress ratio respectively. And the gradient of fatigue crack growth rate decrease in the order of AISI 4337-V steel, ERS and VAR in the region of stable fatigue crack growth. If fatigue crack growth rate are evaluated by using ΔKeff which are calculated at the crack closure point, da/dN fits with one stright line independently of stress ratio. And the effective stress intensity factor range ratio U is the function of only Kmax.(Author)

[en] Hydrogen is studied for its significance in development of delayed fracture of maraging N18K9M5T steel after aging at 430 deg C. Hydrogen affects delayed fracture at +20 deg C; at lower temperatures its effect decreases. Microstresses connected with release of coherent intermetallic particles are suggested to be the main cause of steel at low temperatures

[en] Studies were conducted to investigate the notch sensitivity of deformed thin sheets of an ultra high strength 18 wt. % maraging steel. Geometry and size of specimen and the corresponding holding fixtures were designed for heat treatment and subsequent mechanical testing. The geometry of the notch in the center notch specimens was modified to ensure the reproducibility of the results during its electro-discharge machining. The critical ratios of CC/L and CC/W were kept, as per ASTM standard as 0.7 and 2.6, respectively. CC is center to center distance of loading holes, L is the total length and W is the width of the specimen. Sets of specimens following different thermo-mechanical treatments were tested to establish the sensitivity of the technique. Here results on three series of experiments on specimens from thin sheets of an 18 wt. % Ni maraging steel are presented. Effects of (i) degree of deformation on the notch sensitivity (ii) annealing prior to aging and (iii) cyclic annealing and aging were determined. The technique has proved to be more sensitive than other mechanical testing techniques including hardness, tensile strength and phase analysis using x-ray diffraction. For example, change in the degree of deformation from 75 to 94% increases the hardness values by 12% while the notch strength decreases 2% but the notch strength increases by more than 35 %. Following an annealing aging cyclic, the change in hardness values is only 2-3 % while the value of notch sensitivity changes to more than 20%. (author)

[en] A study was made on the mechanism of titanium effect on the embrittlement under delayed strain of maraging N17K9M5T, N18Ko.M5T steels. It is shown that titanium binds hydrogen in the steel. Conditions, favouring the development of hydrogen embrilement, which depends on structural state of steel and the volume part of the second phase, form at yearly stages of aging during titanium precipitation from solid solution

[en] Quantity of hardening phase formed by intermetallic particles released from the matrix during heating and plastic strain is studied for its effect on maraging N18K8M5T steel strain hardening character. The isotropic-kinematic type hypothesis is used to describe the process of hardening. Phase composition is estimated for its effect on the isotropic/kinematic hardening components' ratio. It is shown that the function, characterizing isotopic hardening component does not depend on the steel state and remains linear in the region investigated. The function, considering kinematic component depends on the phase composition

[en] Wire + arc additive manufacture (WAAM) is a new process for fabricating large-scale metallic components. In this paper, the use of cold metal transfer-based WAAM process for the production of maraging steel bulk material is reported. Process parameters were studied, and the effect of building strategies including oscillation, parallel and weaving on bead shape was investigated. The structural integrity of the WAAM bulk material regarding the surface finish, lack-of-fusion issue and microstructure was characterized. Results proved the feasibility of applying WAAM to producing maraging steel bulk material, and weaving was identified to be most recommended building strategy.