Powders for magnetoabrasive machining

Conclusions On the basis of literature data an analysis is made of the abrasive power and magnetic properties of powders of various magnetoabrasive materials and of the degree of interaction between their magnetic and abrasive constituents. It is concluded that the greatest potentiality for MAP is shown by materials containing a refractory compound powder as their abrasive component and an iron powder as their magnetic component.Translated from Poroshkovaya Metallurgiya, No. 12(168), pp. 63–69, December, 1976.     

Composite SHS materials based on titanium carbide and nikelide doped with a refractory component

This study is devoted to the synthesis and investigation of composite ceramic materials based on titanium carbide and nickelide with the use of the effect of dispersion strengthening by force of the dedicated alloying of reactionary mixtures with a nanodispersed refractory component. The influence of nanodispersed particles on the main combustion parameters in conditions of quasi-isostatic compression is shown. The phase composition and the structure of compact synthesis products, in which the main phase components are TiC and the Ti _x Ni _y intermetallic compound, are investigated. It is established that doping with a nanocomponent does not vary the phase composition qualitatively but leads to a substantial modification of the structure of the materials, at which the average grain size of the main refractory component decreases by a factor of 1.5–3.5. In addition, a similar effect is observed with a decrease in the TiC concentration in the composition of the samples. Complex investigations into the physicomechanical properties and heat resistance of fabricated materials are performed. The effect of the positive influence of refractory nanoparticles on such characteristics of alloys as hardness, strength, Young modulus, and durability to high-temperature oxidation are shown.     

Correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation

This study is concerned with the correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation. The mixtures of TiC, SiC, Ti + SiC, or TiC+SiC powders and CaF₂ flux were deposited on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these mixtures. The surface composite layers of 1.2 to 2.1 mm in thickness were homogeneously formed without defects and contained a large amount (30 to 66 vol pct) of hard precipitates such as TiC and Ti₅Si₃ in the martensitic matrix. This microstructural modification, including the formation of hard precipitates in the surface composite layer, improved the hardness and abrasive wear resistance. Particularly in the surface composite fabricated with TiC + SiC powders, the abrasive wear resistance was greatly enhanced to a level 25 times higher than that of the Ti alloy substrate because of the precipitation of 66 vol pct of TiC and Ti₅Si₃ in the hardened martensitic matrix. During the sliding wear process, hard and coarse TiC and Ti₅Si₃ precipitates fell off from the matrix, and their wear debris worked as abrasive particles, thereby reducing the sliding wear resistance. On the other hand, needle-shaped Ti₅Si₃ particles, which did not play a significant role in enhancing abrasive wear resistance, lowered the friction coefficient and, accordingly, decelerated the sliding wear, because they played more of the role of solid lubricants than as abrasive particles after they fell off from the matrix. These findings indicated that high-energy electron-beam irradiation was useful for the development of Ti-based surface composites with improved abrasive and sliding wear resistance, although the abrasive and sliding-wear data should be interpreted by different wear mechanisms.     

Composition dependence of the abrasive properties of fused titanium and zirconium carbide powders

Conclusions A study was made of the abrasive characteristics of fused TiC_x and ZrC_x powders. The effects were examined of carbon content and grain size on the properties of the carbide phases. Of the carbide phases investigated, the most promising as components of abrasive tools appear to be titanium carbide phases with C/Me ratios of more than 0.75–0.8 and zirconium carbide of stoichiometric composition.Translated from Poroshkovaya Metallurgiya, No. 9 (141), pp. 56–61, September, 1974.     

Effect of niobium,molybdenum, and tungsten on some properties of iron-boride materials

Conclusions A study was made of some key physicomechanical properties of iron-boride materials alloyed with Nb, Mo, and W. The greatest strengthening effect (_t = 62–75 kgf/mm² at 30–33 HRC) is achieved with iron-tungsten matrices infiltrated, using alloyed powders produced by coreduction from oxides, with eutectic Fe-Mo-B or Fe-Nb-Mo-B alloys. The presence of Fe(Nb, Mo)_xB_y type borides in the eutectic alloys substantially increases the heat resistance of the infiltrated materials.Translated from Poroshkovaya Metallurgiya, No. 2(206), pp. 79–82, February, 1980.     

Effect of impurities on the properties of silicon nitride materials

Conclusions The presence of oxides in silicon nitride leads to the formation of an intergranular vitreous phase which has an adverse effect on the high-temperature physicomechanical characteristics of constructional silicon nitride ceramics. This phenomenon is particularly pronounced with silicon nitride contaminated with calcium, silicon, and alkaline metal oxides. Future development work on oxidation-resistant constructional materials based on silicon nitride should go in the directions of removal of impurities and use of additions forming solid solutions or refractory compounds with Si₃N₄ and SiO₂. Additions which can be employed for this purpose include oxides of AI, Mg, Y, and some rare-earth elements.Translated from Poroshkovaya Metallurgiya, No. 1(193), pp. 75–80, January, 1979.     

Abrasive power of titanium carbide and carbonitride

Conclusions In comparisons of the abrasive powers of powders it is necessary to consider their production technology. Only those results are comparable which have been obtained in grinding tests on the same material. In the choice of a powder as an abrasive it is necessary to know its dynamic abrasive power. The character of variation of this property enables optimum abrasive machining conditions to be determined. In the grinding of steels at pressure of up to 75 kN/m² titanium carbide and carbonitride (5 wt. % N) powders surpass electrocorundum in abrasive power during the first 300–500 sec of operation and give a better surface finish. They can therefore be successfully used as grinding powders and micropowders for the preparation of pastes intended for the abrasive machining of steels.Translated from Poroshkovaya Metallurgiya, No. 6(222), pp. 78–81, June, 1981.     

Effect of alloying method on sintering and physico-mechanical properties of Al-A.4% Cu-0.5% Mg powder alloy

Conclusions The method of alloying with copper and magnesium has a strong effect on compacting in sintering and on the physicomechanical characteristics of Al-4.4% Cu-0.5% Mg alloy.The alloy based on Al-0.5% Mg master alloy is characterized by the highest density but its sintering requires higher temperatures (615–635°C) and long holding times. This alloy produced in the optimum conditions is characterized by high physicomechanical properties in the sintered state but by low efficiency of heat treatment. The optimum physicomechanical properties were recorded for the alloy containing the elementary powders of copper and magnesium which was sintered at 595°C for 45 min.Translated from Poroshkovaya Metallurgiya, No. 10(310), pp. 37–41, October, 1988.     

Production of abrasive powders from a silicon nitride base material

Conclusions Optimum conditions of preparation of abrasive powders using scrap from the manufacture of Silinit-R tool material have been determined. The strength of grains of powders investigated is comparable to or higher than, depending on their size, that of AS15 and AS6 synthetic diamond grains. The energy of rupture of their grains substantially exceeds that of grains of a silicon carbide abrasive powder, and grows with increasing filler content. Silinit with the maximum filler content is superior in abrasive ability to titanium carbide or titanium boride but inferior to Kubonit. Abrasive powders from Silinit tool material are suitable for the manufacture of abrasive tools.Translated from Poroshkovaya Metallurgiya, No. 12(300), pp. 26–31, December, 1987.     

Wear behaviour of stainless steel sintered and alloyed with titanium,cobalt and molybdenum

Abstract

In this study, a powder mixture was prepared by adding 1–3 wt-% of FeMo, FeTi and Co powders to the austenitic stainless steel powders and samples were produced by the powder metallurgy method. Attempts were made to establish correlations between the microstructure, hardness, toughness, and abrasive wear values of these samples. Wear resistance of the materials was measured by a two body pin-on-disk wear tester. SiC abrasive papers of 65 μm and 177 μm sizes were used as the abrasive media. Wear tests were performed at the loads of 10, 20, and 30 N at room temperature. They showed that the softer, base austenitic stainless steel exhibited higher mass loss than the alloyed samples. Furthermore, the abrasive wear resistance of the base austenitic stainless steel composites increased with increasing FeTi, FeMo,Co content. The wear rate with the 177 μm SiC abrasive paper increased more than that with the 65 μm SiC abrasive paper.     

Production of amorphocrystalline Ti-Ni coatings by the plasma spray-deposition method

Conclusions Under the action of plasma and the complex processes taking place during the spray-deposition of Ti-Ni coatings, the latter's phase composition changes. It has been established by experiment that such a coating consists of an amorphous phase, the intermetallic compound TiNi, the oxide TiO, and small amounts of complex compounds, possibly of the NiTiO₃ type. The combined amount of the amorphous phase and the intermetallic compound TiNi will determine the main physicomechanical properties of the coating.Translated from Poroshkovaya Metallurgiya, No. 11(287), pp. 36–38, November, 1986.     

Thermodynamic calculations of the cooling of the products of self-propagating high-temperature synthesis in a heat-generating reactor

The cooling of the products of self-propagating high-temperature synthesis in a heat-generating reactor, which is used to synthesize refractory compound powders, is considered.     

Influence of Gas Atomization Parameters of the KhN60M Alloy on the Powder Characteristics for Laser Surfacing

Powders of the KhN60M alloy (EP367, 06Kh15N60M1) are investigated. An overview of manufacturing methods of products of the KhN60M alloy is presented with the analysis of their advantages and disadvantages. It is shown that, when compared with the casting technology and hot pressing of powders of high-alloyed special steels and alloys, additive technologies enable fabricating complexly shaped products with a high level of physicomechanical properties and material utilization factor. The low casting properties of the alloy under study are the reason for the research into atomization to meet the requirements for size, shape, morphology, and fluidity of powders for additive technologies. The goal of this work is to study the influence of the argon pressure during gas atomization on the physical, chemical, and process properties of powders for laser surfacing formed from the KhN60M alloy. The gas atomization technology of the liquid melt by argon using a VIGA 2B laboratory atomizer was used to fabricate the metallic powder of the KhN60M brand at 1560°C and varying the atomizing gas pressure in a range of 22–25 mbar. To select the atomization parameters, the values of the melt viscosity are calculated using the ProCast system for the computer simulation of casting processes by the finite element method and the temperature dependence of viscosity is constructed. The shape and size of the particles and their granulometric composition are studied using laser sedimentation and electron and optical microscopy. The quantitative metallography data are processed using the VideoTest 4 software. The fluidity of powders is measured. It is established that the fraction of spherical particles increases and fluidity of powders improves with an increase in the atomizing gas pressure; the Feret diameter, average particle size, and d₅₀ values vary insignificantly. An experimental dependence of an increase in the yield of the target fraction powder (40–60 μm) with a decrease in the atomizing gas supply is found. The inversely proportional dependence of the fraction of spherical particles on the desired cut fraction is established. The results of the study make it possible to predict the output parameters of powders when atomizing KhN60M steel. Characteristics of powders of the fraction –80 + 40 μm with a shape factor of 0.99 and fluidity of 14–15 g/s make it possible to use them for manufacturing products using additive technologies.

     

Structure formation in magnetoabrasive materials from iron-carbon melts alloyed with carbide-forming elements

Conclusions The structures of magnetoabrasive powders from iron-carbon melts alloyed with carbideforming elements constitute disperse systems which can arbitrarily be divided into two groups: 1) structures characterized by the presence of two distinct types of components — a monocarbide (TiC, Nb₄,C₃, ZrC, or VC), which possesses abrasive qualities, and a ferromagnetic (Fe-Si) matrix, which ensures the necessary magnetic properties, and 2) structures characterized by the fact that abrasive functions are performed by all their structural constituents — a double carbide formed by iron together with an alloying element (Si, Mo, W, or Cr) and a martensitic (bainitic) matrix. The particles of an atomized magnetoabrasive powder from any given alloyed melt have structures differing in macromorphology, which is a result of differences in conditions of solidification of metal drops during melt disintegration. In the presence of carbide-forming elements silicon in an iron-carbon melt dissolves mainly in ferrite, without significantly affecting the morphology of structure of the atomized particles. The effectiveness of magnetoabrasive machining (polishing) depends to a large extent on the choice of abrasive and work materials.Translated from Poroshkovaya Metallurgiya, No. 2(242), pp. 76–84, February, 1983.     

Sintering of Refractory Compound Nanocrystalline Powders. Part 1. Storage and Preliminary Heat Treatment of Titanium Nitride Nanocrystalline Powders

Several approaches are considered for storing and processing finely-dispersed oxygen-free refractory compound powders using the example of titanium nitride nanopowder. The change in composition of nanopowders protected by a surfactant and without protection from oxidation during storage in air, and also during processing in gas atmospheres (nitrogen, hydrogen) and in a vacuum is studied.     

Materials for the protection of surfaces against abrasive wear

Summary The results are presented of a study of the characteristics of abrasive wear resistance of some cermets. It is shown that the use of materials based on refractory compounds enables the life and reliability of machines and mechanisms to be increased. Thus, the life of a mold for the compaction of ferrites was increased 135-fold by using the new materials.     

Synthesis and properties of ceramics in the SiC — B4C — MeB2 system

The effect of impurities and additives of titanium and zirconium borides on the structure and mechanical properties of SiC — B₄C ceramics over a broad temperature range has been investigated. The ceramics was fabricated by hot pressing without a protective medium. Introduction of borides is accompanied by improvement in all the studied mechanical properties at room temperature, and the nature of hardening of the ceramics is practically independent of the type of SiC powders used. At high temperatures, the mechanical behavior of the ceramics is determined by the impurity composition: the ceramics obtained using abrasive powders loses strength beginning at 600°C, while using powders with decreased impurity content makes it possible to preserve the strength of the material up to a temperature of 1400°C. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 29–42, May–June, 2000.     

Electrodeposition of Co-Ni-MoxOy Powders: Part I. The Influence of Deposition Conditions on Powder Composition and Morphology

The Co-Ni-Mo_xO_y powders were obtained electrochemically at a constant current density from ammonia electrolyte. Ni and Co were anomalously deposited, inducing Mo deposition, which cannot be deposited separately from aqueous solutions. The obtained Co-Ni-Mo_xO_y powders were investigated by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electon microscope (SEM) methods. Based on the obtained experimental results, it was concluded that the particle size of deposited powders is influenced by the chemical composition of the electrolyte and current density imposed. XRD results suggested that obtained powders were of amorphous structure, although a Co₃Mo compound can be formed if certain experimental conditions are applied.     

Functional role of the structural constituents of the particles of magnetic abrasive powder

Conclusion As the result of comparison of the service properties of cast magnetic abrasive powders with the same type of structure but different physicochemical properties of the constituents an evaluation was made of the abrasive properties of the latter in polishing of various materials. It was shown that by changing practically only the composition of the solid solution or of the eutectic of the ferromagnetic matrix of the magnetic abrasive powder it is possible to influence both the weight removed and the finish of the polished surface. Similarly the composition of the abrasive inclusions even with the same microhardness may significantly change the polishing indices.Comparative tests of the carbide- and boride-containing powders showed the advantages of the first in polishing of constructional steel and of the second in polishing of stainless steel and titanium and aluminum alloys.Translated from Poroshkovaya Metallurgiya, No. 9(273), pp. 71–75, July, 1985.     

Synthesis of an Aluminum–Erbium Master Alloy from Chloride–Fluoride Melts

Available foreign power-intensive technologies and the absence of domestic production technologies for aluminum–erbium master alloys intended for improving the physicomechanical properties of aluminum alloys make the development of aluminothermic reduction technology of chloride–fluoride melts actual for manufacturing erbium compounds. Thermodynamic analysis of reduction processes is performed for various erbium compounds. Taking into account the physical and chemical properties of erbium compounds, a starting compound, namely, erbium fluoride is found to be preferable. The aluminothermic reduction of the compound from its mixture with sodium fluoride and potassium chloride to form the Al₃Er intermetallic compound is characterized by a high thermodynamic probability. Since data on thermodynamic parameters for erbium complex compound are scanty, they are determined by an indirect method. Experimental data on the aluminothermic preparation of an Al–Er master alloy at temperatures of 750–900°C using melts differing in the ErF₃/NaF ratio and the KCl content are reported; the structure and the phase composition of the prepared master alloy are studied. The phase composition of the flux used for the preparation of the Al–Er master alloy is determined.