Reaction of cubic boron nitride with titanium iodides

Conclusions The reaction of cubic boron nitride with the gaseous phase of titanium iodides (process duration 0.25–2.0 h, total pressure of titanium iodides 100 Pa) results in the preferential formation of TIN in the temperature range 900–1200°K and of titanium nitride and titanium diboride at 1200–1300°K.Translated from Poroshkovaya Metallurgiya, No. 10(262), pp. 57–59, October, 1984.     

A stereological analysis of the formation of the structure of WC-Co alloys during consolidation of the carbide powder

Conclusions The change in distribution of particle dimensions, the obtaining of a regular alternation of phases, and the development of inter- and intraphase boundaries in the alloy produced based on powder the production method of which included firing, reduction, and carbidization at increased temperatures occurred at a higher rate.The author expresses thanks to V. A. Ivensen and O. N. Éiduk for materials submitted for the investigation and also to V. P. Novichkovaya and A. S. Potapov for help in conducting the experiment.Translated from Poroshkovaya Metallurgiya, No. 3(279), pp. 65–69, March, 1986.     

Titanium base antifriction materials (Review)

Conclusions The low antifriction properties of titanium and its alloys are caused by seizing of the rubbing surfaces as the result of adhesion of titanium, the high coefficient of friction (0.48–0.68), and the low wear resistance and thermal conductivity (8.38–16.76 W/m·K).Surface hardening of titanium alloy parts is applicable only for light operating conditions. It does not solve the problem of the antifriction properties of titanium as a valuable metal for the parts of rubbing pairs.Work in the area of the powder metallurgy of titanium confirms the possibility of the creation of a new class of titanium alloys with the necessary combination of antifriction properties.Translated from Poroshkovaya Metallurgiya, No. 1(253), pp. 80–90, January, 1984.     

Mechanical and hydraulic characteristics of P/M titanium filters

Conclusions For the production, by hydrostatic pressing, of filters from PTÉK, PTÉS, and PTÉM electrolytic titanium powders and a screened 0.63–1.0 mm fraction of the powder forming during the crushing of TG-Tv titanium sponge, the recommended pressure range is 78.5–157 MPa. The mechanical strength of filters from screened TG-Tv powders is, other things being equal, 1.2–4 times higher than that of filters from electrolytic powders. The filtration indicators (coefficients of permeability and filtration) of filters from screened TG-Tv and electrolytic powders are generally virtually identical, but with coarse (0.63–1.0 mm) electrolytic powders they are two to seven times higher than with electrolytic powders.Translated from Poroskhovaya Metallurgiya, No. 7(235), pp. 34–39, July, 1982.     

Assessment of damping capacity of porous titanium nickelide under forced oscillation conditions

We have studied the damping capacity of porous titanium nickelide powder on a laboratory apparatus designed for vibration of materials under steady-state forced oscillation conditions. We have established the dependence of the damping capacity on the porosity and the magnitude of the applied force. By comparing tests of porous titanium and titanium nickelide, we show that the latter has better damping characteristics. We hypothesize two levels of damping in titanium nickelide: interparticle and lattice.Institute of Problems in Materials Science, Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 89–92, January–February, 1994.     

Effect of annealing on the structure and properties of fused titanium carbide

Conclusions It has been established that, under the action of thermal stresses set up during rapid cooling after high-temperature heating, titanium carbide undergoes plastic deformation. This manifests itself in the appearance of slip bands, on which excess carbon is precipitated. With increase in annealing time, these bands decrease in number and increase in size. At the points of intersection of slip bands, flocculent graphite precipitates are formed.Annealing at 1400–1600°C leads to the formation of large equilibrium titanium carbide grains and precipitation of excess carbon on their boundaries. Annealing at 2000–2200°C produces a microstructure with large equilibrium grains, excess carbon in this case being precipitated at the points of intersection of linear defects. Stabilization of thermoelectrical characteristics is achieved after annealing for 4 h at temperatures of 1600–2200°C.Translated from Poroshkovaya Metallurgiya, No. 10 (94), pp. 78–82, October, 1970.     

Optimization of the process of manufacture of diamond-containing composite materials based on titanium carbide-steel alloys

Conclusions A study was made of the conditions of production of tungsten-free composite materials by sintering in a high-pressure chamber and in vacuum. Good-quality nonporous specimens of titanium carbide-steel materials cannot be produced by hot pressing in graphite dies. The hardness of materials sintered in a HPC is higher (81–86 HRA) than that of materials sintered in vacuum (75–82 HRA.). Heat treatment slightly lowers it (to 77–85 HRA). The highest wear resistance is exhibited by vacuum-sintered materials. In alloys sintered in a HPC a directional orientation of the steel binder with titanium carbide grain inclusions was observed. In service tests the properties of composition diamond-containing materials based on titanium carbide-steel alloys were found to match those of Tvesal alloys-diamond-containing composites based on a tungsten-group hard metal.Translated from Poroshkovaya Metallurgiya, No. 7 (259), pp. 21–25, July, 1984.     

Obtaining the Ni-TiC composite powder by the carbidization of titanium nickelide

The goal of this study is to investigate the mechanism and kinetics of carbidization of the titanium nickelide powder, which allows one to obtain the Ni-TiC composite powder. It is established by experimental methods and theoretical analysis that, in the temperature range 1000–1200°C, this process proceeds in the internal mode with the decomposition of NiTi and with the formation of a nickel-based solid solution with dispersed titanium carbide particles distributed in it. It is shown that, with the carbon excess in the starting charge, the final product consists of a nickel matrix, including ～3 at % carbon and traces of titanium, and particles of almost stoichiometric titanium carbide. With the deficiency of carbon in the starting charge, the Ni matrix contains ～1.1 × 10^?2 at % carbon and >0.65 at % titanium, while the particles of titanium carbide have the composition TiC_0.5-TiC_0.8. The suggested model of this process allows one to evaluate the time that the NiTi particles completely decompose and qualitatively describe the time dependence of the particle size of titanium carbide.     

The effect of production conditions on the structure formation and on the electrical conductivity of hotpressed materials in the system nitride-silicon carbide

Conclusions n materials of the system Si₃N₄-SiC are hot-pressed, there occur processes of carbidization of Si₃N₄ and of reduction of the surface film of SiO₂ accompanied by weight loss and increased concentration of SiC. The degree of such physicochemical transformations is well correlated with the magnitude of the specific weight losses. The electrical conductivity of the investigated materials is basically determined by the content of the conducting phase SiC in the initial charge; however, when the concentration of the introduced silicon carbide is low, then the amount of secondary SiC forming in hot pressing plays a considerable role.Translated from Poroshkovaya Metallurgiya, No. 2(290), pp. 51–54, February, 1987.     

Procedure for Choosing Abrasive Composites for Grinding Materials that are Hard to Machine

A procedure is developed for choosing a composite abrasive for grinding alloys that are hard to machine based on considering the interaction of tool materials and the article being machined. The efficiency of the procedure is demonstrated using the composite created for machining titanium alloys.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 31–38, January–February, 2005.     

Rheological characteristics of magnetic-abrasive powders in a magnetic field

The size of particles of magnetic-abrasive powders, magnetic induction in the working zones of magnetic gaps, and the size of working zones have been studied for their effect on tangential and normal stresses which develop in magnetic-abrasive tools during polishing. Friction coefficients for the powder in magneticabrasive tools and in a tool—titanium pair are determined.Kiev Polytechnic Institute. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 62–66, January–February, 1994.     

Wettability of aluminum nitride by molten metals

The sessile drop method has been used with a vacuum of 2.10^–3 Pa to examine the wettability of aluminum nitride by fourteen molten pure metals as well as the effects of adding chromium, vanadium, niobium, tantalum, and titanium to the liquids on the wetting angle in systems containing aluminum nitride and liquid tin, copper, and germanium. Aluminum nitride is wetted only by molten silicon and aluminum. Out of the elements examined, titanium is the most adhesion-active for this ceramic. The results are examined from the viewpoint of thermodynamic wetting theory.Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 74–78, May—June, 1996. Original article submitted June 29, 1994.     

Formation of the phase composition of tungstenless hard alloy powder with mechanochemical synthesis

Carbon and nickel are studied for their effect on the formation of phase composition of tungsten-free hard alloy powder prepared by mechanochemical synthesis. It is established that the phase formation of this powder is governed by the initial titanium carbide stoichiometry. If titanium carbide has a nonstoichiometric composition, the alloy structure corresponds to the three-phase equilibrium TiC_1–x-Ni₃Ti-Ni, and otherwise it corresponds to the equilibrium TiC-Ni.Translated from Poroshkovaya Metallurgiya, No. 11(359), pp. 21–24, November, 1992.     

Oxidizability of materials based on TiC and TiN at elevated temperatures

Conclusions The addition of titanium nitride and niobium carbide to the alloys based on TiC with the nickel-molybdenum binder (TN type) increases their oxidation resistance in air at high temperatures (1173–1273°K). The alloys based on the titanium carbide and nitride and alloyed with the niobium carbide with the nickel-molybdenum binder (NTN) have higher oxidation resistance in air than the commercially produced TN20 and T15K6 alloys.The equations of the kinetic curves of oxidation in air of the TN20 and NTN alloys were derived; at temperatures of 1173 and 1273°K, the curves are almost linear, starting at a holding time of 10 min.Translated from Poroshkovaya Metallurgiya, No. 4(304), pp. 76–78, April, 1988.     

State of oxygen in fine titanium nitride powders

Conclusions Oxygen in fine titanium nitride powders produced by the plasma-chemical method can exist in three forms — replacing the nitrogen in the nitride, forming oxide films, and adsorbed on the surface. In the course of the plasma-chemical synthesis of titanium nitride 1–5 wt. % of oxygen from the starting reactants becomes statistically distributed throughout the particles, forming homogeneous titanium oxynitrides. Contact with humid air results in the formation, on the surfaces of small particles, of thin ( 1-nm) oxide films characterized by activation-type conduction and in adsorption of some oxygen. The composition of the main volume of each particle remains unchanged.Translated from Poroshkovaya Metallurgiya, No. 9 (225), pp. 6–9, September, 1981.     

Titanonitriding kinetics of hard metals

Conclusions TiN coatings have been obtained on hard metals by heating the latter in an environment consisting of nitrogen and a titanizing mixture. The formation and growth of TiN on a preheated hard metal occur as a result of gaseous-phase transport of titanium and nitrogen to the hot surface of the metal. The formation of TiN is a chemical reaction of the first order. The rate constant of the reaction is an exponential function of process temperature, and has the following values: for VK20 alloy K=16.5 exp (–29,330/RT) and for T30K4 alloy K=0.74 exp (–19,260/RT), where R=2 cal/g · mole · degC. The time dependence of the specific weight gain of titanonitrided hard alloys is limited by the amount of the titanium carrier compound in the gaseous phase, which varies according to the exponential law C e^–kt at K=2.3, 3.2, and 3.9 h^–1 for VK20 alloy and K=3.2, 3.9, and 4.6 h^–1for T30K4 alloy.Translated from Poroshkovaya Metallurgiya, No. 6(210), pp. 53–56, June, 1980.     

Physicochemical interaction and structure development during the formation of metal gas-transfer coatings on diamond (review). 1. Kinetics

Work devoted to studying the phase composition and thickness of chromium, titanium, molybdenum, vanadium, and tungsten coatings which form on diamond powder during vacuum annealing of this powder mixed with chromium powder or oxidized powders of Ti, Mo, V, and W is analyzed. Coatings consist of metal (Cr, Ti, Mo, V, W) and carbide (Cr₇C₃, Cr₃C₂, TiC, -Mo₂C, V₂C, VC, W₂C, WC) phases. Diffusion of carbon during coating growth with increased metallizing time and temperature causes carbidization of chromium, titanium, and vanadium (it causes a reduction in the content of metal phase and an increase in carbide phases is coatings), growth of higher carbides (Cr₃C₂, VC, WC) at the expense of lower carbides (Cr₇C₃, V₂C, W₂C), and filling of carbon vacancies in the lattices of TiC and VC. Saturation of coatings with carbides correlates with the temperature-time range in which a further increase in coating weight slows down.Translated from Poroshkovaya Metallurgiya, No. 7(355), pp. 34–40, July, 1992.     

Thermodiffusional treatment of chromium carbide hard metals

Conclusions It has been established that the cementing phases of P/M chromium carbide and titanium carbide hard metals can be superficially hardened by thermodiffusional impregnation with phosphorus. Treatment of these alloys for 3–7 h at 1000°C in an alumina filler containing 30–70% of nickel phosphide and subsequent 1-h annealing at 400°C increase the surface hardness of their binder phases by 1.5–3 GPa. Thermodiffusional treatment doubles the wear resistance of KKhN35 alloy operating under hydroabrasive wear conditions.Translated from Poroshkovaya Metallurgiya, No. 12(240), pp. 69–73, December, 1982.     

Plasma coatings made from magnetite and their use in electrolysis installations

Spraying parameters for plasma coatings made from commercial magnetite powders of different particle size on steel and titanium substrates are studied. On the basis of microstructure, phase composition, and bond strength as functions of the initial particle size optimum spraying parameters are obtained for preparing magnetite coatings 300–1500 m thick. The results are used for spraying active layers on sheets 250 × 500 mm in size for electrodes in electrolytic water purification.Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 52–56, May-June, 1996. Original article submitted June 3, 1994.     

Composite magnetoabrasive TiC-Fe,VC-Fe,and Cr-C-Fe powders

Conclusions A study was made of the conditions of direct synthesis of composite MAMs from the simple substances. It has been established that the heating of mixtures of powdered carbide-forming transition metals (Ti, V, and Cr), carbon black, and iron in the temperature range 1300–2000°C results in preferential formation of titanium and vanadium carbides which are uniformly distributed in an iron matrix in the form of globules. The shape and size of the globules are determined by the carbide concentration in the composite and synthesis conditions. The chromium carbide Cr₃C₂ is not easy to synthesize in the presence of iron. The boundaries of fields of synthesized titanium and vanadium carbides in an iron matrix are clearly defined. The extent of carbide-iron interpenetration is negligible, not exceeding 3–7% of the carbide grain (globule) diameter. In the series Ti-V-Cr the degree of chemical reaction of these carbide-forming metals and their carbides with iron increases from titanium to vanadium and chromium. On the basis of data yielded by this investigation, a method is proposed for producing titanium carbide- and vanadium carbide-containing iron-base composite MAMs; the optimum compositions and conditions of synthesis of such composites have been determined. Pseudofused composite MAPs containing titanium and vanadium carbides possess excellent physicomechanical properties (grain strength, abrasive ability, and specific saturation magnetization intensity), and can be recommended for machining various materials, in particular steels. The results obtained have been utilized in the development of TU 6-09-4575-78 for MAMs, on the basis of which such materials are now being produced on an industrial scale at the Donetsk Chemical Reagents Factory.Translated from Poroshkovaya Metallurgiya, No. 3(243), pp. 94–100, March, 1983.