Showing papers on "Carbide published in 1970"

The effect of carbide and nitride additions on the heterogeneous nucleation behavior of liquid iron

Abstract: A systematic study of carbide and nitride additions on the heterogeneous nucleation behavior of supercooled liquid iron was undertaken. It was found that titanium nitride and titanium carbide were very effective in promoting heterogeneous nucleation. These compounds were followed by silicon carbide, zirconium nitride, zirconium carbide, and tungsten carbide in decreasing order of effectiveness. The degree of potency of the nucleation catalysts is explained on the basis of the disregistry between the lattice parameters of the substrate and the nucleating phase. Through the inclusion of planar terms the Turnbull-Vonnegut “linear” disregistry equation was modified to more accurately describe the crystallographic relationship at the interface during heterogeneous nucleation.

The wetting of carbon by copper and copper alloys

Abstract: The effects of alloying additions on the wetting of two types of carbon, HX30 graphite and vitreous carbon, have been investigated, with a view to developing a system for metal impregnation of carbon fibre assemblies. Pure copper is inert and non-wetting but two additions caused the copper to wet: Cr on both substrates and V on the vitreous carbon only. Many of the additions formed a carbide reaction layer at the interface, and in the two wetting systems this was a thin, continuous, coherent layer. The data have been analysed in terms of the chemical and physical properties of the system and it was found that the wetting behaviour of copper alloys on HX30 graphite and vitreous carbon could be explained in terms of the behaviour of the reaction product carbides of the alloying addition when these existed.

Method of producing refractory carbides,borides,silicides,sulfides,and nitrides of metals of groups iv,v,and vi of the periodic system

Abstract: A METHOD OF PRODUCING REFRACTORY INORGANIC COMPOUNDS SUCH AS CARBIDES, BORIDES, NITRIDES, SILICIDES, OXIDES, PHOSPHIDES, SULPHIDES, FLUORIDES AND CHLORIDES OF METALS OF THE IV, V AND VI GROUPS, IN WHICH AT LEAST ONE OF THE METALS OF THE IV, V AND VI GROUPS OF THE PERIODIC SYSTEM IS MIXED WITH ONE OF THE NON-METALS N, C, B, SI, O2, P, S, F, OR CL2 AND TO THE RESULTING MIXTURE IS INTRODUCED IGNITION MEANS FOR GENERATING A TEMPERATURE SUFFICIENT FOR STARTING THE PROCESS OF COMBUSTION OF THE INITIAL COMPONENTS WHOSE FURTHER INTERACTION TAKES PLACE OWING TO HEAT HENERATED BY THE REACTION, THE REACTION OF METALS WITH METALLOIDS, C, B, SI, P, S BEING CARRIED OUT IN AN INERT GAS MEDIUM.

Sintering steel-bonded carbide hard alloy

Abstract: A sintered alloy comprising a carbide of preferably titanium and a steel matrix of an alloy steel containing chromium, molybdenum, copper and vanadium as alloying elements provide high temperature hardness and wear resistance. Preferred alloys contain 0.8 to 1.9% by weight of manganese and up to 80% by weight of carbide.

Structure and properties of tantalum carbide crystals

Abstract: Single crystals of tantalum carbide, up to 2 mm in size have been grown from solution in a bath of molten iron. The slip plane was found to be {111} using a two-surface analysis on etch-pitted crystals deformed by microindentation at room temperature. Observations of etch-pit patterns around inclusions suggest that slip occurs on other planes at elevated temperatures. Maximum microhardness values between 3800 and 5200 Knoop (100 gm load) were found at a composition TaC0.83±0.01. In regions of crystals with a carbon content less than TaC0.83 a phase transformation was seen close to microhardness indentations in samples decarburised below 2200† C. The mechanical behaviour of tantalum carbide is discussed with reference to a general model for the electronic structure of carbides.

Method for manufacturing composite articles containing boron carbide

Abstract: In accordance with the invention, a composite silicon impregnated boron carbide body bonded to a backing material for said body is manufactured by forming a boron carbide powder compact of the desired shape and size, coating a surface of the compact with boron nitride powder, impregnating the boron nitride coated boron carbide powder compact with silicon, removing from the surface of said body at least most of the boron nitride layer and any silicon deposited thereon, and then bonding the silicon impregnated boron carbide body to the organic resin backing material.

Hardnesses of Carbides and Other Refractory Hard Metals

Abstract: In a carbide or biboride the excess binding energy associated with metal—metalloid interactions must be overcome for a dislocation to move through the crystal structure. This makes possible a simple calculation of the indentation hardness number in terms of the heat of formation and the molecular volume. Good agreement with measurements is found for twelve representative compounds.

Electrolytic capacitor employing paste electrodes

Abstract: A high-capacitance, low-voltage electrolytic capacitor consists essentially of a pair of paste electrodes and a separator saturated with electrolyte which functions as an electronic insulator and an ionic conductor. One of said electrodes is composed of active carbon and the opposing electrode is composed of refractory hard boron carbide or a refractory hard metal carbide or boride wherein the metal may be tungsten, titanium, tantalum, niobium or zirconium, said electrodes being prepared by mixing finely divided particulate material of the above compositions with electrolyte to form a viscous paste and compressing the paste to form the electrodes.

Metallic surface treatment method

Abstract: THE METALLIC POWDER PRODUCED FROM A TERNARY ALLOY OF TI, AL AND C, HAVING A DISJPERSION OF TI2ALC COMPLEX CARBIDE IN A MATRIX OF TI OR AL OR THEIR ALLOYS, PREFERABLY THE BINARY TI2AL WITH THE TI WITHIN THE GAMMA RANGE OF THE TI-AL PHASE DIAGRAM AND AVOIDING DETRIMENTAL AMOUNTS OF TIAL3, ALLOWS ACCURATE CONTROL OF THE DEPOSITION OF EITHER OR BOTH AL AND TI OR THEIR ALLOYS IN A DIFFUSION PACKTYPE METHOD FOR COATING AN ARTICLE. DEPOSITION IS BROUGHT ABOUT THROUGH THE USE OF A HALIDE SALT ACTIVATOR PREFERABLY IN THE FLUORIDE OR CHLORIDE CLASS.

Process for forming high density refractory shapes and the products resulting therefrom

Abstract: A PROCESS FOR FABRICATING LOW POROSITY, ESSENTIALLY DEFECT FREE, COMPOSITE REFRACTORY SHAPES OF NOVEL COMPOSITION. A POWDERED REFRACTORY MATERIAL IS MIXED WITH A CARBON CONTAINING SUBSTANCE AND THE MIXTURE IS COLD FORMED INTO A DESIRED SHAPE, THE PREFORMED SHAPE IS THEN HEAT TREATED TO CONVERT THECARBON CONTAINING SUBSTANCE TO CARBON. A MOLTEN METAL BATH IS PREPARED, COMPRISED OF AT LEAST TWO METALS, AT LEAST ONE OF WHICH IS CAPABLE OF REACTING WITH THE CARBON IN THE PREFORMED SHAPE, AND THE COMBINATION OF WHICH RESULTS IN A METALLIC MIXTURE GREATER THAN THAT OF THE REFRACTORY MATERIAL MAING UP THE MATRIX OF THE PREFORMED SHAPE. THEPERFORM IS THEN HEATED AND IMPREGNATED WITH THE MOLTEN METAL WHICH RESULTS IN SINTERING OF THE REFRACTORY MATERIAL MATRIX, AND THE REACTION OF AT LEAST ONE OF THE METALS WITH THE CARBON CONTAINED IN THE INTERSTICES FORMED BY THE PARTICULATE REFRACTORY MATERIAL, TO FORM METAL CARBIDE(S) THEREIN. THE COMPOSITE SHAPE IS THEN REMOVED FROM THE MOLTEN METAL BATH AND COOLED. BECAUSE THE COEFFICIENT OF THERMAL EXPANSION OF THE MIXTURE OF METALS IS CLOSE TO OR SLIGHTLY GREATER THAN THAT OF THE REFRACTORY MATRIX, THE COMPOSITE SHAPE COOLS TO ROOM TEMPERATURE ESSENTIALLY FREE OF CRACKS AND RESIDUAL STRESS.

Heat resistant high strength composite structure of hard metal particles in a matrix,and methods of making the same

Abstract: A high strength structure made of hard metal particles, such as metal carbide particles, brazed to each other in a porous lattice of a first brazing metal or alloy, the voids and spaces in the brazing metal or alloy being filled by a solidified second brazing metal or alloy of a melting point lower than the melting point of the first brazing metal or alloy. The second brazing metal or alloy may also contain a dispersion of hard metal particles, such as metal carbide particles, generally of a smaller size than that of the original hard metal particles. The structure is made by mixing a predetermined proportion of hard metal particles with the first brazing metal or alloy in the form of a powder, and by sintering in a furnace so as to obtain a substantially porous structure, followed by a second pass in the furnace of the porous structure covered with the second brazing metal or alloy in a powder form so as to impregnate the porous structure with the melted second brazing metal or alloy.

Thermal Conductivity of Transition Metal Carbides

Abstract: Transition metal carbides, such as TiC, exhibit very low thermal conductivities (K) at low temperatures. The lattice conductivity at such temperatures is severely limited by phonon scattering by conduction electrons. At high temperatures, point-defect scattering of phonons by carbon vacancies in the non-stoichiometric compounds dominate K. Scattering of electrons by the vacancies limits the electronic contribution. Above ~1000oC the thermal conductivity of the carbides is increased by ambipolar diffusion.

SOME RELATIONS BETWEEN THE STRUCTURE AND MECHANICAL PROPERTIES OF WC–TiC–Co ALLOYS*

Abstract: The relationship between the mechanical properties and the structure of the sintered carbide WC–TiC–Co has been studied. Specimens containing 7 and 15% cobalt were sintered at temperatures between ...

Process for making nickel-based superalloys

Abstract: A process for making nickel-based superalloys that possess excellent high-temperature properties which includes the steps of providing a metal powder having a controlled amount of oxygen and carbon which is confined and densified at an elevated temperature forming a billet that can be further deformed, if desired, to provide an appropriate shaped component. Thereafter, the billet or deformed part is subjected to heat treatment to effect a growth in the grain size thereof to attain optimum physical properties, whereafter the alloy is carburized to increase the carbon content thereof to a level in excess of about 500 parts per million (ppm) which is performed in a manner so as to preferentially promote carbide formation at the grain boundaries of the alloy, thereby stabilizing the alloy against further grain growth when subjected to elevated temperatures during use.

OBSERVATION OF SiC WITH Si(111) ‐ 7 SURFACE STRUCTURE USING HIGH‐ENERGY ELECTRON DIFFRACTION

Abstract: Using grazing‐angle high‐energy electron diffraction (HEED) epitaxial crystallites of β‐Sic have been observed on Si surfaces simultaneously with the silicon fractional‐order surface structures. SiC has not been observed with the LEED technique under comparable experimental conditions. The surfaces containing SiC were prepared by iodine desorption. Surfaces prepared by oxide decomposition at 1200 °C or by in situ pyrolysis of SiH4 were carbide free. The experiments showed the carbide was due to decomposition of a carbon adsorbate.

The oxidation of iron-carbon alloys at low temperatures

Abstract: The formation of thin oxide films (<1000 A) on polished iron-carbon alloys in the temperature range of 200–350°C and in 100 Torr of dry oxygen was investigated. A combination of vacuum microbalance and transmission electron microscopy techniques were employed to characterize the oxidation process kinetically and morphologically, respectively. The initial oxide formation on the iron-carbon alloys obeyed a two-stage logarithmic kinetic mechanism with activation energies of 0.26 eV and 0.32 eV for the first and second stage, respectively. These kinetics and activation energies are in agreement with the two-stage logarithmic kinetic theory developed by Uhlig, assuming electron transfer as the rate-controlling mechanism. Logarithmic kinetics were followed by parabolic kinetics with an activation energy of 1.08 eV, indicating cationic grain boundary diffusion as the rate controlling mechanism. The oxide formed over the iron-carbon alloys at 300°C was primarily due to the oxidation of the ferrite phase, but a thin protective oxide film (~ 150 A) was formed on the carbide phase. At later stages, a lateral growth of the oxide crystallites formed over the ferrite phase resulted in a gradual coverage of the carbide phase. This lateral growth was the major effect of the second phase on the oxidation of two-phase iron-carbon alloys. A systematic study of the effect of the phase boundary length on the oxidation of iron-carbon alloys was quantitatively evaluated.

Methods and significance of particle and grain-size control in cemented carbide technology*

Abstract: The paper reviews work demonstrating the importance of carbide particle and grain size as regards the preparation and the properties of cemented carbides, and considers the techniques of particle- and grain-size measurement. It is shown that the initial size of the carbide powder influences the grain size in the sintered structure. Means of size-distribution analysis are evaluated. Some problems of accurate quantitative structure analysis and its automation are discussed. The best methods at present available for routine and basic work are outlined and modern devices are described.