Carbide Solid Solution Research Articles

Increased liquid droplet erosion resistance of steam turbine blades

AbstractAlloys used for the blades of steam turbines usually do not show a satisfactory resistance to erosion and require surface protection with suitable coatings. Starting from the results obtained with Stellite 6 coatings on AISI 420 stainless steel blades, this research has been developed with the aim to increase erosion resistance by modifying the chemical composition of the coatings. Several samples have been coated by laser cladding and exposed to liquid erosion tests. In particular, concentrations of carbide forming and solid solution strengthening elements have been varied in order to establish their effects against liquid droplet erosion. Results of the tests and EDX analyses on the samples are reported, with a discussion on the various effects on erosion resistance. Two directions have appeared as the most promising, either increasing the concentration of carbide forming elements, or increasing the concentration of nickel in the coatings.

Electronic energy structure of AlxSi1−x C wide-gap semiconductor crystals

The electronic structure of silicon carbide solid solutions with aluminum has been studied within the limits of a single approximation. The local coherent potential method in terms of multiple scattering theory was used. The electronic spectrum was analyzed in comparison with the experimental X-ray spectra of silicon, aluminum, and carbon. The nature of the observed features of the electronic spectrum is interpreted, and Al-Si covalent binding in solid solutions is found. Formation of vacant states with energies of 1 Ry and decreased forbidden gap in the XANES spectrum at higher aluminum contents in crystal are discussed.

Surface segregation of ZrC from a carbide solid solution

The surface segregation of zirconium carbide from carbide solid solutions is investigated. The spontaneous surface segregation of ZrC grains from solid solutions in the pseudobinary ZrC-NbC system is revealed for the first time. It is demonstrated that the ZrC precipitation is associated with the decomposition of the car-bide homogeneous solid solutions Zr1−xNbxC ≡ (ZrC)1−x(NbC)x. The boundaries of the latent solid-phase decomposition region formed at T<1200 K are determined for the solid solutions formed by ZrCy and NbCy′ carbides with different nonstoichiometry. The experimental and theoretical estimates obtained for the segregation energy of ZrC are equal to −50 and −31 kJ mol−1, respectively.

A Nanocomposite Ceramic Based on the Powder of a Carbon-In-Silicon Carbide Solid Solution

The synthesis of a nanocomposite powder of a solid solution of carbon in silicon carbide with controlled content of nitride phases is considered. A method of activated sintering for molding a pore-free nanocomposite ceramic with superior mechanical properties is proposed. Microstructure of the sintered ceramic is examined.

Synthesis of Aluminum Nitride–Silicon Carbide Solid Solutions by Combustion Nitridation

AlN–SiC solid solutions were synthesized via a combustion nitridation process. Reactions between powder mixtures of aluminum, silicon, and carbon or aluminum with β‐SiC and gaseous nitrogen under pressures of 0.1–8.0 MPa are self‐sustaining once they have been initiated. Investigations were made with reactant ratios of Al:Si:C = 7:3:3, 6:4:4, and 5:5:5 and Al:SiC = 7:3, 6:4, and 5:5. For the Al‐Si‐C system (molar ratio of 6:4:4), the maximum combustion temperature was dependent on the nitrogen pressure, increasing from 2300°C to 2480°C with an increase in pressure, from 0.1 MPa to 6.0 MPa. In all cases, the product contained the solid solution as the primary phase, with minor amounts of silicon. The amount of unreacted silicon decreased as the nitrogen pressure increased; the presence and dependence of unreacted silicon on pressure has been explained in terms of the volatilization of aluminum. The full width at half maximum for the (110) peak of the AlN–SiC solid solution decreased as the nitrogen pressure increased, which indicated the formation of a more homogeneous product.

Non-Oxide CMC Formation by Reactive Melt Infiltration

Non-oxide ceramic matrix composites (CMCS) in the system Mo-Si-B-C were formed by a reactive pressureless melt infiltration process at 1450°C and 1800°C, respectively. For the high temperature process a porous preform of pure boron carbide powder was infiltrated by a silicon melt containing 8 mol% of molybdenum. For the low temperature process, however, a mixture of boron carbide and molybdenum powder (1:1.5) was used as the preform to be infiltrated by a pure silicon melt. The fully dense reacted matrix materials are composed of MoSi 2 , SiC, boron carbide solid solutions. minor amounts of molybdenum- and silicon-borides and residual free silicon. The bending strength was 130 - 170 MPa, a Young's modulus of 300 GPa and a Vicker's hardness of 20 GPa were obtained.

日本新金属（株）におけるタングステンとモリブデンの製造

JNM was established in 1963, as a joint venture between Mitsubishi Materials and Awamura Mining. Over the last 30 years, JNM has made significant development in product techniques and production facilities for its range of Tungsten and Molybdenum.Tungsten metal and carbide powders production in JNM has increased from 70 and 50 tonnes per month in 1981 to 220 and 200 tonnes in 1992, respectively by installing large fully automatic reduction furnaces designed and built in-house, and various types of carburizing furnaces for special use.Our other products of Tungsten and Molybdenum and their main use are following. Trioxides for pigments, catalysts, electronics components. Ammonium parasalts and metasalt for catalysts. Hetero polic acid and their salts for catalysts. High purity products for electronics components. Borides and Silicides for advanced cermics. Carbide solid solution powders for hard metal. “Hardlett” powders for hard facing.

Lattice Constants of Boron Carbides

The lattice constants of boron carbides have been determined by powder X‐ray diffraction for samples with compositions between about 7.7 and 20.5 at.% carbon. The boundaries of the single‐phase region are at about 9 at.% carbon and near, but likely somewhat less than, 20 at.% carbon. The composition dependence of the lattice constants thus established provides a method of assessing the carbon concentration of unknown materials. In particular, assignment of the approximate composition of single crystals used in previous studies allows for a systematic examination of changes in interatomic separation as a function of composition. These changes are discussed in terms of a structural model of the boron carbide solid solution.

Effects of tungsten content on the creep-rupture properties of low-carbon cobalt-base heat-resistant alloys

The effects of tungsten (W) content up to about 20 wt pct on the creep-rupture properties of low-carbon HAYNES 25-(L-605-) type cobalt-base alloys were investigated at 1089 and 1311 K. An increase in W content of about 5 wt pct resulted in tripling the rupture life without significant loss of creep ductility at 1311 K. The principal strengthening phases precipitated during creep at 1311 K were W solid solution and M6C carbide precipitates in the matrix and on the grain boundaries. The amounts of these precipitates, especially precipitates of W solid solution, increased with increasing W content. The Cr23C6 carbide was also detected in those ruptured specimens of alloys containing more than 17 wt pct W. The creep ductility decreased a little, and the rupture life did not increase with increasing W content at 1089 K. Two types of carbides (Cr23C6 and M6C), Co2W (Laves phase), and α-Co were confirmed in the specimens ruptured at 1089 K. The amount of Co2W harmful to ductility, as well as the amounts of strengthening phases (carbides), increased with increasing W content.

Preparation and pyrolysis of a polymeric precursor for the formation of titanium nitride (TiN)-titanium carbide (TiC) solid solutions

Preparation and pyrolysis of a polymeric precursor for the formation of titanium nitride (TiN)-titanium carbide (TiC) solid solutions

Carbide composition change during liquid phase sintering of a wear resistant alloy

Constitutive liquid phase sintering is used to obtain fully dense parts of powdered STELLITE Alloy No. 6 PM (Co-29Cr-4.5W-l.2C- < 1B) with excellent wear resistance at elevated temperature. This alloy is characterized by a cobalt-rich fcc solid solution and interdendritic carbide phases in the as-atomized state. Compositional changes in the carbides prior to, and during, the liquid phase sintering were investigatedvia X-ray diffraction, optical microscopy, and Auger electron spectroscopy. The rejection of boron and cobalt by an M23C6-type carbide was identified as leading to the local formation of the liquid phase. A mechanism for the interactive role of the carbide composition change and the constitutive liquid phase sintering is proposed.

Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems

Duplex microstructures of iron-base superalloys, consisting of an austenitic matrix and a M7C3 carbide, can be produced within the Fe-Mn-Cr-Mo-Al (Si)-C systems. The stability regions of the carbides were inspected by means of isothermal sections of alloys in the quinary combination Fe-Mn-Cr-Mo-C for 70 at% metal and 30 at % carbon. For 35 at % iron the competing carbides are found to be M2C, M3C and the molybdenum cementite (MoFe2C) in the arc-melted state, with M23C6 in the annealed state. In the quaternary system, Fe-Mn-Mo-C, a M2C carbide forms, presumaby derived from a solid solution carbide, (Mn, Mo)2C. In extracted carbides of cast alloys containing Fe-Mn-Cr-Mo-Al (Si)-C a considerable amount of the π-phase carbide occurs.

ＷＣ‐ＴｉＣ‐ＺｒＣ‐Ｎｉサーメットにおける微細炭化物組織

The carbide structure of WC-17%TiC-40%ZrC-5%Ni cermet was mainly studied. It was found that the cermet showed an extremely fine carbide structure with high hardness and high strength when sintering cycle was specified. The structure was attributed to the phase separation of carbide solid-solution from one-phase to two-phases. Such a fine structure would similarly be obtained in other alloy systems.

Some properties of alloys of zirconium and niobium carbides in their homogeneity ranges

1. A study was made of the effects of composition upon the intensity of electroerosion, microhardness, electrical resistivity, and CTE of alloys of zirconium and niobium carbides in their homogeneity ranges (C/Me=0.82–0.98). 2. The properties investigated were found to have extreme values at the equimolar composition, indicating that MeIV-MeV bonds play the dominant role in the total bond energy characterizing the formation of carbide solid solution in these alloys.

Fractured Structure around Vickers Hardness Indentation in TiC-Mo-Ni Cermets

A peculiar structure was found to develop around Vickers hardness indentation in TiC base cermets, whereas it has never developed in WC base cemented carbides. Therefore, in this report, the above structure was investigated at room temperature using various cermets with various Ni, C and Mo contents and carbide grain size.As the result, it was made clear that the structure was mainly associated with trans- and intergranular cracks of carbide under the heavy stress generated by Vickers impression, so that it was considerably influenced by various factors as shown above. The fractured structure was considered to be due to lower strength and plasticity of titanium carbide solid solution than those of WC. These results would be a help for understanding the mechanical properties of cermets.

Phase decomposition and grain growth in (W,Ti) C-Co-alloys

The object of this study was to obtain information on the inhomogeneous structure of the WC-TiC solid-solution phase after sintering with cobalt or nickel acting as binder. For this purpose, the solubility of WC in TiC was determined at temperatures from 1500 to 2100° C. Furthermore, grain growth and phase decomposition behaviour were investigated in the temperature ranges 1450 to 1550° C and 1700 to 1850° C. Phase-decomposition of oversaturated mixed carbide solid solution which is not capable of further coarsening enabled the reaction constant at the solid-liquid interface to be determined.

Thermal-Stress Crack-Initiation Method for Ranking Ceramic Materials

A test is described which permits ranking of brittle materials according to their resistance to thermal fracture under steady-state conditions. A water-cooled probe and a small, thin, annular disk specimen heated by a radiator are used. Tests on AUC graphite and on a series of composites of transition-metal pseudobinary solid-solution carbides with graphite were very reproducible and reliable. A thermal-stress analysis for the graphite agreed well with the test results.

Preparation of TIC-WC and NBC-WC solid solutions and study of their superconductivity

TiC-WC and NbC-WC carbide solid solutions were prepared in this work by simultaneous synthesis from a mixture of the metals with carbon black in a hot-compaction press.

Fast Reactor Rocket Engines—Criticality

Critical sizes are determined for a variety of fast assemblies appropriate for nuclear rocket reactors. These are based on cores of UO/sub 2/-W cermets or UC-metal carbide solid solutions reflected by beryllium. Rocket reactors weighing as little as 200 lb are possible, and, in larger sizes, either high power density or high exit gas temperature can be achieved. The fast spectrum allows the use of the most refractory materials (such as HfC) in bulk to obtain high performance. Use of U/sup 233/ in place of U/sup 235/ can lead to substantial improvements in reactor weight, specific power, and/or temperature capability at the cost of the radiation associated with U/sup 233/. The core sizes are generally quite small, which is valuable where shielding may be signiflcant. Nuclear aspects, including control, uranium investment, power distribution, and reflector materials, are briefly discussed. (auth)

Wear processes on cemented carbide tools used in cutting steel

The conditions of wear from the faces of cemented carbide cutting tools are described. The particular conditions on the top surface of a cutting tool where the thin ribbon, or chip, of metal with a freshly exposed surface flows in contact with the tool over a relatively long path, lead to the generation of high temperatures at the friction surface. Examination of the worn top surface of tools of two types, one consisting of tungsten carbide and cobalt and the other of tungsten carbide, titanium carbide and cobalt, have shown that in cutting steel an alloy is formed between the steel and the tungsten carbide at temperatures of ca. 1300° C and this leads to very rapid wear. Grains of a titanium-tungsten carbide solid solution which are present in cemented carbides containing titanium carbide resist alloy formation with the steel at these high temperatures. The presence of titanium carbide greatly reduces the rate of wear. Consideration of the phenomena of wear on such tools presents a picture of the type of temperature gradient in the tool near the friction surface.