Phase equilibria in the solidification range of alloys of the Ti-Ru-Ir system

Conclusions The processes taking place during solidification of the alloys of the Ti-Ru-Ir ternary system have been examined for the first time. The results show that the system contains three nonvariant quaternary equilibria with the liquid of the incongruent type: L + + at 2220°C, L + + at 1920°C, and L + + at 1465°C.In the region with the composition 0–50% Ti, the processes take place in the direction to the Ti-Ru side of the concentration triangle where they are also completed at the temperature of the binary eutectic L '+ equal to 1855°C. In the region with the composition 50–100% Ti the processes are completed at 1460°C at the nonvariant point corresponding to the eutectic reaction L + of the Ti-Ir binary system.Translated from Poroshkovaya Metallurgiya, No. 11(299), pp. 72–77, November, 1987.     

The phase equilibria in W-Fe-Co-Ni system alloys. II. Isotherms of the solidus and the phase composition of alloys containing 10 and 20% (Fe + Co + Ni) at temperatures above 1200°C

Conclusions The isostructural intermediate -phases Fe₇W₅ and Co₇W₆ in the W—Fe—Co system form a continuous series of -solid solutions. In the 1640–1630°C range the L + (Fe₇W₆) peritectic equilibrium in this system changes to a similar L + (Co₇W₆) equilibrium, where is the tungsten-base boundary solution.In the W-Fe-Co-Ni polythermal tetrahedron in the 1470–1460°C range conversion of the L +(Fe₇W₆)+, peritectic equilibrium into the similar L + (Co₇W₆) + , where is the nickel-, -ironcobalt-base boundary solution, occurs.Upon completion of crystallization at 1400°C, the W-Fe-Co system alloys with 10–20% (Fe + Co) have a + phase composition, while the W-Fe-Co-Ni system alloys with 10–20% (Fe + Co + Ni) accordingly have + , + + or + . At temperatures below 1215°C in alloys rich in iron, FeW may be formed instead of -phase and therefore the alloys may have an + FeW, + + FeW, + + + FeW and + + FeW phase composition.Translated from Poroshkovaya Metallurgiya, No. 5(281), pp. 86–89, May, 1986.     

Electric-spark alloying of steels with WC-Co hard metals

Conclusions A study was made of the electroerosion and cathode weight increase accompanying the ESA of steels with WC-Co hard metals and of some properties of resultant alloyed layers. In ESA the best results are obtained with VK20 alloy under soft conditions and with VK15 alloy under hard condition. The optimum alloying time is 5–10 min/cm² in process No. 2 and 3–5 min/cm² in process No. 5. Under these conditions ESA by the soft process (with VK20 alloy) ensures the formation of a hard (2200 kgf/mm²) white layer of the same thickness (40 m).Translated from Poroshkovaya Metallurgiya, No. 8(212), pp. 67–71, August, 1980.     

Phase equilibria in W-Fe-Co-Ni system alloys. I. Alloys containing 10% (Fe + Co + Ni) at 1400–1200°C

Conclusions The isostructural intermediate -phases of Fe₇W₆ and Co₇W₆ in the W-Fe-Co system form a continuous series of solid solutions and transformation of the L + peritectic equilibrium into, the similar L + (Co₇W₆), occurring in a narrow temperature range (1640–1630°C) is observed. In the W-Fe-Co-Ni system in the 1470–1460°C range transition of the L + (Fe₇W₆)+ peritectic equilibrium into the similar. L + (Co₇W₆+ is also observed.Upon completion of crystallization and at temperatures of 1400–1200°C alloys of the primary section with 10% (Fe + Co + Ni) have a two-( + or +) or three-phase (+ +) structure. In alloys rich in iron at temperatures below 1215°C FeW may form instead of (Fe₇W₆) phase.Translated from Poroshkovaya Metallurgiya, No. 4(280), pp. 60–64, April, 1986.     

Deformation structure ofα-SiC single crystals

Conclusions The deformation of-SiC single crystals in bending with the direction of extension and compression approximately parallel to the basal face (the axis of bending parallel to (0001), T = 2000–2100°C) involves slip over the basal plane; the directions of slip are <11¯20> and <10¯10>. Accordingly, crystallographic planes rotate about parallel axes, <10¯10> and <11¯20>. Slip in the <10¯10> direction may be a consequence of migration of dislocations with Burgers vectors equal to b=2/3 <10¯10> (a full dislocation and <10¯10> (a partial dislocation). X-ray microdiffraction observations show [12] that partial dislocations with Burgers vector components parallel to [101¯1] frequently form in-SiC; travel of partial dislocations apparently plays an important part in the deformation of -SiC. The deformation of-SiC is accompanied by kink band formation [1].During the deformation process, dislocations pile up in slip planes, and their density increases by two to three orders; their distribution is very uneven, typical values of being 10⁸–10¹⁰ cm^–2 and values of _max of 10¹¹cm^–2 being recorded in zones with a large local curvature.Because of the changing specimen structure, two stages may be detected in the deformation process: 1) formation of elastically bent regions and 2) comminution (formation of microcracks within the specimen).The crystals investigated exhibited only micropolygonization, when the block size in the basal plane was 30 and the block disorientation 10. Neither postdeformation annealing for 10–30 h at 2000–2100°C nor prolonged (4–8 h) holding of specimens under load produced any macroscopic polygonization. The structure of naturally deformed specimens, too, was found to contain no polygonization macroblocks. It would appear that, because of the appreciable activation energy for diffusion and strong covalent linkage in-SiC, dislocations cannot readily climb over large (>10) distances in this compound; in this connection, the relaxation properties of-SiC would be expected to be weak.The methods of investigation employed in our work are comparatively simple to use. They do not give any information about elementary deformation acts, but throw a light on the character of lattice variation in various volumes (V ranging from 0.1t to 6.0t mm³, where t=200–500 is the crystal thickness) and are particularly useful in topographic x-ray photography when there is no contrast on individual linear defects in crystals.Translated from Poroshkovaya Metallurgiya, No. 8 (128), pp. 63–72, August, 1973.     

Thermodynamic properties of alloys of the manganese-silicon system in the ranges of existence of the silicides “Mn9Si9” and “Mn6Si”

Conclusions The Gibbs energy, enthalpy, and entropy of formation of phases based on the compounds Mn₉Si₂ and Mn₆Si at 690–850°C have been determined by measuring the emf's of concentration galvanic cells.Translated from Poroshkovaya Metallurgiya, No. 7(235), pp. 67–70, July, 1982.     

Static and cyclic strength of a uniaxially reinforced material in bending (part 1)

Conclusions A built-up degree of damage =f/f_o 8% has virtually no effect on the static strength of an AD33-B CM operating in air. The arbitrary fatigue limit corresponding to this volume of damage on a basis of 2–10⁵ cycles may be taken to be equal to (0.5–0.55) _t. Accelerated buildup of damage on a basis of 2–10⁵ cycles is observed at _a > (0.5–0.55) _t.Translated from Poroshkovaya Metallurgiya, No. 7 (259), pp. 65–67, July, 1984.     

Error in the determination of the particle-size distribution of a powder with a laser analyzer

Conclusions Simple expressions have been obtained from known parameters of a flow-type chamber for estimating errors in laser analyzer measurements of the main numerical particle size distribution characteristics of powders obeying the logarithmic normal law. It is shown that, in spite of marked errors (Fig. 1) in size measurements on single particles whose trajectories are deflected from the laser beam center, it is possible to attain high accuracy in the measurement of numerical particle distribution characteristics by suitable choice of aero or hydrodynamic particle stream focusing [5] (Table 1: maximum error in the determination of the amount of the main fraction in a powder of particle size 3/2 _f = 1.9% at 2_j = 15 and _f = 4.3% at 2_j = 72 m). Without good particle stream focusing, measurements may be very inaccurate (Table 1: _f = 24% at 2_j = 120 m and _f = 55.5% at 2_j = 170 m). The accuracy of laser analyzer measurements grows with increasing curvature (coefficient n) of analyzer calibration characteristics and vice versa. The q/qt relationships obtained may find application in the assessment of errors in particle size analyses of powders with particle distributions differing from the logarithmic normal law.Translated from Poroshkovaya Metallurgiya, No. 12(288), pp. 15–20, December, 1986.     

Resistance of materials based on silicon nitride to corrosion by solutions of some acids and alkalis

Conclusions Hot-pressed silicon nitride parts of 1.5–4% porosity containing a 10 wt. % activating addition of MgO are resistant to corrosion by nitric acid at room temperature and by 1% NaOH solution at 100°C under steady-state conditions. The presence of 1–20 wt. % CaF₂ added with the aim of improving antifriction properties results in corrosion in nitric acid, obeying the law m²=K, where K 5.5·10^–5· C³ %²/h). The corrosion is due to attack on specimens by hydrofluoric acid forming during the reaction between the CaF₂ and HNO₃.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 70–72, January, 1980.     

Hot pressing and vacuum sintering of fine titanium nitride powder

Conclusions Increasing the specific surface of titanium nitride from 18 to 90 m²/g lowers the initial recrystallization temperature of loosely poured powder from 1300 to 600°K. The temperature at which blanks attain practically 100% density in the hot pressing of finely divided titanium nitride (a starting powder particle size of 0.05–0.07 m) is 1600°K, which is 500–700°K below the temperature level of full sintering of relatively coarsegrained powders (a particle size of about 0.5 m). At hot-pressing temperatures above 1800°K a fall in the density of sintered compacts is observed, which is apparently attributable to the beginning of nitrogen evolution from the nitride and also to the formation of microcracks. In vacuum sintering without a plasticizer, crack formation lowering the density of specimens by 3–4% is characteristic of the whole sintering temperature range. The grain size in hot pressing and vacuum sintering is practically the same, being determined chiefly by the sintering temperature and time. At the maximum specimen density the maximum grain size is 20 m.Translated from Poroshkovaya Metallurgiya, No. 12(204), pp. 27–32, December, 1979.The authors wish to thank V. I. Berestenko, T. N. Miller, and D. I. Medvedev for the provision of titanium nitride specimens.     

An X-ray diffraction study of the oxidation of Ni3Ti

Conclusions A layer-by-layer x-ray diffraction phase analysis was made of the scale formed on Ni₃Ti during atmospheric oxidation over the temperature range 600–1000°C. The scale was found to contain the oxides NiO, NiO · TiO₂, TiO₂ (rutile), Ti₃O₅, and Ti₂O₃ as well as two nickel phases — pure nickel and a nickel solid solution. The pattern of distribution of these phase constituents in consecutive scale layers is outlined.Translated from Poroshkovaya Metallurgiya, No. 5 (137), pp. 57–62, May, 1974.     

Some mechanical properties of silicon carbide fibers

Conclusions Electroerosion of silicon carbide fibers in contaminated mercury electrical contacts decreases their strength by between one-half and two-thirds. During prolonged holding under load at room temperature the creep of silicon carbide fibers is close to zero, while at 1173°K l/l 10^–7 l/day. X-ray structural analysis of silicon carbide fibers annealed for (1.8–10.8)·10³ sec in a hydrogen atmosphere at 1273–1773°K and for (3.6–18)·10³ sec in a nitrogen atmosphere at 1773–1973°K revealed no recrystallization in (4–5)·10^–7-m-thick layers of polycrystalline SiC deposited from a gaseous phase. A correlation was found between the strength of silicon carbide fibers and the number of flashes forming during their fracture.Translated from Poroghkovaya Metallurgiya, No. 1(253), pp. 55–59, January, 1984.     

Influence of grain size and porosity on the high-temperature friction of titanium carbide

Conclusions It was established that in friction of a TiC-TiC pair in vacuum the coefficient of friction at 250C and the wear rate at 1250C are practically independent of grain size. At higher temperatures these characteristics have an inverse relationship to grain size.It was shown that with an increase in porosity both the wear rate and the coefficient of friction increase. With an increase in temperature the influence of porosity on the wear rate decreases.With variations in porosity in the 1–10% range, in grain size in the 1–50 m range, and in temperature in the 20–1500C range the wear rate changes within limits of 10–45% and the coefficient of friction within limits of 3–35%.Translated from Poroshkovaya Metallurgiya, No. 9(297), pp. 56–61, September, 1987.     

Boundaries of the single-phase side fields of the system Mo-Cu-Ni in the solid state

Conclusions It was established that the molybdenum corner of the Mo-Cu-Ni ternary system contains a singlephase field of solid solutions of copper and nickel in molybdenum with a combined Cu and Ni content of 1.5–2 wt.%. At the copper-nickel side of the constitution diagram of this system, there is a single-phase field of ternary Cu-Ni-Mo solid solutions, whose molybdenum content steadily rises with increase in nickel concentration, from 1.5 wt.% at NiCu=2080 to 3 wt.% at NiCu=4060.Translated from Poroshkovaya Metallurgiya, No. 2 (122), pp. 65–70, February, 1973.     

Comparison of diffusion calculations for two models of powder mixtures

Summary The advantages and drawbacks are discussed of two models of powder mixtures: The model based on single-particle approximation and the concentric sphere model. Calculated values obtained by using both models are compared with experimental data.Translated from Poroshkovaya Metallurgiya, No. 1, pp. 23–24, January, 1968.     

Some features of the manufacture of R-100F-1 carbonyl iron powder

Conclusions Raising the temperature in the reactor increases the concentrations of carbon and nitrogen impurities in a carbonyl iron powder, the increase in the nitrogen content being greater than that in the carbon content. A rise in reactor temperature increases both the goodness factor Q_reland the temperature coefficient of magnetic permeability TC. Increasing the rate of feed of ammonia to the decomposition reactor brings about a growth in the concentration of nitrogen in a carbonyl iron powder, which lowers the TC of the powder and at the same time slightly decreases its goodness factor Q_rel. The optimum conditions for the manufacture of a starting R-100 powder of lower TC. (not more than 80·10^–6 1/deg C) are: upper, middle, and lower zone temperatures of 311, 306, and 337°C, respectively, an ammonia concentration in the decomposition products of 9 vol. %, and an iron pentacarbonyl feed rate of 32 liters/h. For the manufacture of R-100F-1 powder, the fine powder fractions from cyclones 2, 3, and 4 are used. The quantitative yield of carbonyl iron powder is 1.5–1.7%.Translated from Poroshkovaya Metallurgiya, No. 5 (221), pp. 1–5, May, 1981.     

Effect of heat treatment on the structural state and mechanical properties of polycrystals based on the superhard boron nitride modifications

Conclusions An investigation was carried out into the effect of thermal cycling on the structural state of polycrystals based on the high-density boron nitride modifications. It is shown that a two-phase material is characterized by a high level of macro- and microstresses, which control its brittle rupture behavior and mechanical properties. In particular, microcracking processes initiated by internal stresses after the application of external load promote stress relaxation at the tip of a propagating macrocrack, thereby imparting high fracture toughness (K_c 16–18 MN/m^3/2) to the material. During heat treatment (performed in this work at T 800°C) internal stress relaxation takes place, which is accompanied by a fall in fracture toughness to the level characteristic of unstressed single-phase sintering (K_c 10–14 MN/m^3/2) and changes in hardness and rupturing stress.Translated from Poroshkovaya Metallurgiya, No. 1(217), pp. 53–61, January, 1981.     

Structure,mechanical properties,and special features of failure of nickel-based detonation coatings

Conclusions Alloying nickel with chrome, aluminum, and boron, as well as the variation of the spraying conditions makes it possible to control purposefully the composition, structure, and properties of the detonation coatings. In alloying nickel with aluminum and chrome, the strength properties of the coatings are fully utilized at thicknesses not greater than 0.25 mm. The adhesion strength of these coatings to the titanium substrates is 35–150 MPa, to steel substrates 20–120 MPa, in the thickness range 0.1–0.3 mm. The ductility properties of the coating are utilized only to 40–60% in comparison with the dense material of the same composition. The ductility of the coatings is reduced most markedly by additions of aluminum and boron, whereas the addition of chrome causes the smallest reduction.Alloying nickel with chrome increases its cohesion strength and heat resistance, alloying with aluminium reduces heat resistance, creep strength, and wear resistance, and combined alloying with aluminum and boron reduces wear and heat resistance.The soft conditions are optimum for depositing coatings on titanium substrates. Under these conditions, particles are only welded without high deformation, whereas medium conditions with moderate temperature and kinetic parameters are optimum for depositing the steel components. This gradation is caused by the susceptibility of the titanium alloys to brittle failure in the presence of surface defects and cracks and also by a large difference in the coefficients of thermal failure of the materials of the coating and the substrate and higher chemical activity of titanium.Failure of coatings of alloyed nickel alloys takes place by means of intergrain delamination which is preceded by plastic deformation of the materials of the coating and the substrate. Only simultaneous alloying with aluminum and boron results in a slightly different fractographic pattern because these additions embrittle the material of the coating.Translated from Poroshkovaya Metallurgiya, No. 7(343), pp. 53–61, July, 1991.     

Kinetics of external dissolution of metals in metallic melts. (Review)

Conclusions Dissolution rate under diffusion conditions is usually controlled by three parameters, D, , and c_m. Since the dependence of D and values on the individual properties of metals (D 10^–5 cm²/sec, 10^–3 cm) is slight,dissolution rate under diffusion conditions is determined chiefly by cm, which thus constitutes the principal criterion governing the choice of a metal compatible with any given melt. Dissolution under kinetic conditions does not appear to be typical of metals, since even tungsten, which has the highest crystal lattice energy of all metals [62], dissolves under diffusion conditions [19, 20, 63–66].It thus follows that detailed researches into the dissolution kinetics of metals in metallic melts are hardly likely to reveal any new corrosion-resistant metallic materials. The existing liquid-metal corrosion inhibitors are refractory compounds such as nitrides or carbides [67]. This does not mean, of course, that investigations into the dissolution kinetics of solid metals in metallic melts serve no useful purpose, since they are concerned not only with corrosion, but also with a number of other processes referred to in the introduction to this survey.Translated from Poroshkovaya Metallurgiya, No. 8 (92), pp. 39–54, August, 1970.     

Interrelationship between the properties of powders,the conditions of pressing and sintering,and the structure of porous niobium

Conclusions With an increase in niobium powder particle size the pressability increases while the formability decreases. There is a linear relationship between the normalized radius of the pores in high-porosity niobium powder specimens and the normalized volume of the pores. This is an indication of geometric similarity of the disposition and form of the pores in specimens pressed from niobium powders with different degrees of dispersion.The product of the coefficient of side pressure and the coefficient of friction on the die wall is 0.053 ± 0.10. This means that with reasonable values of the coefficient of friction of dispersed niobium powder on the wall of the steel die is 0.14.Translated from Poroshkovaya Metallurgiya, No. 3(327), pp. 30–33, March, 1990.