Structure and properties of 10Γ2ΦБ steel after hot plastic deformation

Recrystallization in 10Γ2ΦgB steel (strength class K60) is investigated. The influence of key parameters of two-stage thermomechanical treatment on the ferrite grain size and the work of impact is shown. Thermomechanical treatment of 10Γ2ΦgB steel intended to improve the strength and viscoplastic properties is tested industrially.     

Structure and properties of κ-carbides in duplex lightweight steels

Abstract

κ-Carbide in lightweight steel has been studied. Its thermal stability, crystal morphology, orientation relationship, degree of lattice misfit and mechanical properties have been measured experimentally. The mechanisms for the microstructural evolution of κ-carbide are considered based on the crystal structure, lattice misfit, element diffusivity and solute partition. The hard γ/κ grain and ductile α+κ grain provide an opportunity to develop lightweight steels with a desirable combination of mechanical properties.     

Flow properties of tool steel powders for selective laser melting – influence of thermal and mechanical powder treatments

In powder bed fusion additive processes the flow properties of the powder influence the quality of the final component and the efficiency of the process. In this investigation an attempt is made to identify flowability indicators which can describe the flow performance of the powder during the powder layering (i.e. recoating) step; common to all powder bed fusion processes. To this end, shear tests were performed by means of a powder rheometer. Bulk density, flow function and degree of cohesion were measured. The results suggest that there is a good correlation between the aforementioned parameters and the flowability of the powder during SLM processing. In addition, it was found that thermal treatments and tumbling enhance flowability. Thermal treatments were performed at 150, 200 and 250°C for a period of 10?min and in air.     

Influence of defects on the ductility of liquid 9X2MΦ and 75X3MΦ steel

Viscosimetric data on liquid 9X2MΦ and 75X3MΦ steel taken from working rollers of a reversible rolling mill with different ultrasonic behavior illustrate the influence of defects recorded in ultrasound monitoring on the temperature and time dependence of the liquid steel’s kinematic viscosity. A Krautkremer ultrasonic defectoscope is employed in monitoring. The viscosity of the liquid steel is measured by means of damping torsional oscillations of a crucible with melt in heating and subsequent cooling in the range 1500–1580°C.     

Structure and properties of strip for large-diameter pipe made from steel in strength categories Kh80–Kh100

We studied structure formation in high-strength strip for trunk pipelines made from steel in strength classes Kh80–Kh100. The structural morphology was shown to have an effect on the mechanical properties of the thick rolled sheet. Weldability studies and low-temperature brittle-fracture-resistance studies were performed on the steels developed as part of this study.     

Production,sintering, and application of nanocrystalline iron–copper additions in a powder steel

A method is proposed for activated sintering of a sprayed iron powder by the coalescence of pressed particles through fine-grained layers based on iron–copper nanodispersed (ND) additions. The mechanical properties of composite materials containing 2% Fe–Cu ND addition are higher than those of the materials prepared from a mixture of standard powders by a factor of 1.5.     

Laws of nitriding of alloy steel in a plasma–arc remelting furnace

Metal drop samples are taken during plasma–arc remelting of 12Kh25N16G7AR steel billets. An analysis of the drops shows that the fraction of steel nitriding in the drops accounts for 20–40% of the total steel nitriding at a nitrogen content of 0.06% in a billet. An equation is derived to estimate the nitriding of a liquid Cr–Ni–Mn steel from the nitrogen concentration in the billet to be remelted.     

Composition of C–Si–Mn–Cr–W–V powder wire and quality of surfacing

The influence of the composition of powder wire on the properties of the applied layer on steel samples is studied in the laboratory. If amorphous graphite in 35V9Kh3SF powder wire is replaced by material containing carbon and fluorine, the porosity of the applied layer is reduced, and fewer nonmetallic inclusions (including row oxide inclusions and undeformable silicates) are present. Statistical analysis of the experimental data illustrates the influence of the carbon equivalent of the 35V9Kh3SF powder wire on the hardness of the applied layer (including the mean surface hardness and the microhardness of martensite). With increase in the carbon equivalent calculated by the Paton Institute’s formula, the hardness of the applied layer linearly increases.     

State of Ni–Cr–B–Si–Fe/WC coatings after plasma powder surfacing with nanopowder modifier

The structure and phase state and internal stress fields of plasma powder Ni–Cr–B–Si–Fe/WC surface coatings are compared in the presence and absence of a modifier: Al₂O₃ nanoparticles. PS-12NVK-01 powder alloy applied to a steel 20 substrate is studied by transmission diffraction electron microscopy of thin films, scanning electron microscopy, and X-ray structural and local X-ray spectral analysis. The phase composition of the alloy is determined; its defect structure and internal stress are studied. The structure of the material is analyzed before and after the introduction of Al₂O₃ nanopowder in the melt. Introducing the modifier reduces the grain size of the material; leads to the formation of tungsten carbide W₂C and the boride Fe₃Ni₃B in the carbide subsystem; and reduces the internal stress and scalar dislocation density.     

Starch consolidation of M3/2 high speed steel powder – influence of microstructure on mechanical properties

Abstract

The influence of microstructure on the mechanical properties of starch consolidated super solidus liquid phase sintered AISI type M3/2 high speed steel powder has been evaluated. Hardness measurements, Rockwell C indentation and scratch testing were used to evaluate the mechanical properties and light optical microscopy and scanning electron microscopy were used for post-test characterisation. The results show that it is possible to starch consolidate and sinter large particle size high speed steel powder to obtain microstructures with high mechanical strength. However, the results show a strong correlation between the as sintered microstructure and the resulting mechanical properties and illuminate the importance of having a dense and isotropic microstructure in order to meet engineering requirements in demanding applications. Consequently, the failure mechanisms observed during indentation and scratch testing can be related to residual pores, present in the low temperature sintered samples, and a coarse microstructure with eutectic carbides, present in the high temperature sintered samples.     

Modelling of the temperature and the velocity of ceramic powder particles in a plasma flame—I. Alumina

A theoretical model has been developed to evaluate the temperature and velocity of a spherical particle at any instant during its flight in a plasma flame. Computations, which have been made for an alumina particle in this part (Part I) of the study, showed that neglecting temperature gradient in liquid film or solid core will lead to error in calculation of particle temperature and velocity. But this error is comparatively less for larger Al₂O₃ particles (about 50 μm) than for smaller ones (below 25 μ). This has been explained in terms of the negligible extent of size reduction of the particles due to the large values of heat of vaporisation and thermal conductivity of alumina. This vaporisation aspect has also been verified experimentally.     

Modelling of the temperature and the velocity of ceramic powder particles in a plasma flame—II. Zirconia

The model developed in Part I of this study, has been extended to a ZrO₂ particle here. It was found that the temperature and the velocity of a ZrO₂ particle, computed by assuming a constant average plasma temperature, deviate significantly from those calculated by considering the variation of the plasma temperature with the distance from the nozzle, as in the actual case. Again, it was found that the particle size reduction due to vaporisation cannot be neglected for particles moving close to the axis of the flame. The injection distance and the injection velocity were identified as two important spray parameters. It was noted that ZrO₂ particles within a certain size range should be used for developing coatings. The computations also revealed that the particles travelling in the peripheral region of the flame, do not undergo complete melting. It was experimentally verified that the particle size reduces significantly due to vaporisation.     

Impact properties of sintered and wrought 17–4 PH stainless steel

Abstract

Charpy V notch (CVN) impact testing was conducted on full size and subsize specimens of sintered and wrought 17–4 PH stainless steel (17–4 PH SS) in the as sintered and H900 heat treated conditions. Test geometries correspond to the American Society for Testing and Materials (ASTM) and Metal Powder Industries Federation (MPIF) impact testing standards. Merits of a notched specimen compared with an unnotched specimen were analysed for both the wrought and sintered materials. The notched ASTM standard bars had a lower coefficient of variance for impact energy than the unnotched MPIF standard bars and displayed greater toughness. Porosity and grain size have a detrimental synergistic effect on impact toughness for the sintered material. Following a discussion about the differences in the wrought and sintered microstructures, it is recommended that impact testing of the injection moulded and sintered specimens should be evaluated according to the ASTM test specifications.     

Effect of microstructure evolution on Lüders strain and tensile properties in an intercritical annealing medium-Mn steel

The influence of microstructural characteristics on Lüders strain and mechanical properties was explored by means of altering thermo-mechanical circumstances in...     

Structure and thermal properties of the matte of the autogenous smelting of copper–zinc concentrates

The phase composition and the structure of the solidified mattes of the autogenous smelting of copper–zinc concentrates containing 49.8 and 61.0% Cu in Vanyukov’s furnace are studied. The forms of the main elements (Cu, Ni, Fe, S, O) and the accompanying impurities (Zn, Pb, As, Sb, Co, Sn, Au, Ag) in the rich matte are determined. The phase-transformation temperatures in cooling of the mattes in an inert or oxidizing gas atmosphere are found.     

Fabrication of in situ TiB2–TiC reinforced steel matrix composites by spark plasma sintering

Abstract

In situ TiB₂ and TiC particulates reinforced steel matrix composites have been fabricated using cheap ferrotitanium and boron carbide powders by spark plasma sintering (SPS) technique. The sintering behaviour and the formation mechanism of the composite were studied. The results show that when the composite was sintered at 1050°C for 5 min, the maximum relative density and hardness of the composite are 99·2% and 83·8 HRA respectively. The phase evolution of the composite during sintering indicates that the TiB₂ and TiC reinforcements were formed in situ as follows: first, the solid/solid interface reaction between Fe₂Ti and B₄C, resulting in the formation of a small amount of TiB₂ and TiC below 950°C; second, the solid–liquid solution precipitation reaction in the Fe–Ti–B–C system, resulting in the formation of the main TiB₂ and TiC reinforcements at ～1000°C.