Friction Surfaces and Wear Products of Sn–Sb–Cu-Based Composite Materials

The structure and the tribological properties of the composite materials based on an Sn–Sb–Cu alloy (B83 babbit) and fabricated by hot pressing of powders are studied under dry sliding friction conditions. Modified schungite and silicon carbide are chosen as reinforcing materials. The composite material fabricated by a powder technology and reinforced by silicon carbide and modified schungite particles is found to have the doubled wear resistance as compared to a cast B83 alloy at a comparable friction coefficient.     

The compaction of silicon carbide and compositions based on it: An analysis of domestic and foreign experience

Domestic and foreign experience in compaction of silicon carbide and compositions based on it in order to produce construction and shock resistant materials is generalized. The size, phase, and other characteristics of carbide powders of different producers are compared, and different production variants of compaction (solid-phase sintering, hot isostatic pressing, and sintering in high-pressure chambers), the relation of thermal-force parameters and properties of obtained materials, and the nanolevel of powders and forming structure are considered.     

Hot pressing of binary titanium-chromium diboride

Conclusions An experimental study was made of the process of densification of a binary titanium-chromium diboride powder. The dependence of the relative density of hot-pressed specimens on temperature, applied pressure, and pressing time was determined. An analysis of experimental data carried out within the framework of the theory of volume viscous flow of a porous solid has shown that densification in the hot pressing of a binary titanium-chromium diboride powder is effected through creep of its particles. The creep is controlled by the dislocation climb mechanism. Determinations were made of specific rates of steady-state creep for the particles of the binary titanium-chromium diboride powder; the specific rate of steady-state creep was found to be proportional to the square of stress. The energy of activation for steady-state creep of the binary titanium-chromium diboride powder was calculated.Translated from Poroshkovaya Metallurgiya, No. 5(209), pp. 69–72, May, 1980.     

Modification of the structure of powder coatings on nickel and chromium-nickel bases by introducing nanoparticles of titanium diboride during electron-beam welding

Composite materials and coatings that contain titanium diboride in a metal host are widely used with the purpose of fabricating high-strength heat-resistant materials. Due to high hardness as well as heat and corrosion resistance, titanium diboride is a promising compound for use as a wear-resistant component of the composition “metal host-TiB₂.” The structure and mechanical properties of compositions TiB₂-PG-10N-01 and TiB₂-PKh20N80, which were obtained by a three-stage method involving the preliminary mechanical treatment of mixtures of elemental powders, the self-propagating high-temperature synthesis (SHS) reaction initiated in the activated mixture, and the subsequent mechanical treatment of the product of the SHS reaction, are investigated. To form the coatings, the method of electron-beam welding is applied.     

LABORATORY VACUUM HOT PRESS TO 2500°C

Abstract

The advantages of using vacua in the hot pressing of refractory materials are demonstrated. A simple apparatus is described which enables powders to be pressed at temperatures up to 2500°C at gas pressures of < 3 μ Hg. Results with zirconium diboride (ZrB₂) show that samples of > 95% theoretical density can be prepared with an impurity oxygen content of the order of 0.01 wt.-%.     

制备工艺对碳化硼陶瓷性能的影响

以活性炭和碳化硅为烧结助剂,采用真空热压工艺,制备了碳化硼陶瓷材料.研究了真空热压工艺、烧结助剂对碳化硼陶瓷性能及断口的影响,结果表明,以活性炭和碳化硅为烧结助剂的碳化硼陶瓷随热压压力增加,开口孔隙度减小,相对密度和抗弯强度增加.添加活性炭的碳化硼陶瓷在热压压力为35MPa下,开口孔隙度有最小值(1.7%),相对密度(91.7%)和抗弯强度(277.6MPa)达最大值;以碳化硅为烧结助剂的碳化硼陶瓷在热压压力为30MPa下,开口孔隙度有最小值(0.66%),相对密度(91.9%)和抗弯强度(173.6MPa)达最大值.添加活性炭的碳化硼陶瓷随保温时间由30min增加到90min,开口孔隙度逐渐减小而相对密度逐渐增加(90min时分别达到0.19%、99.6%),抗弯强度先增加后减小,在保温时间为60min时抗弯强度达到最大值(351.7MPa).在相同的真空热压工艺下,添加活性炭的碳化硼陶瓷与添加碳化硅的碳化硼陶瓷相比,其开口孔隙度低,抗弯强度高.初步探讨了真空热压工艺以及添加剂促进碳化硼陶瓷烧结的机理.     

Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.

     

Influence of the forming process and sintering conditions on the structure and properties of powder ferrite materials

The effect of uniaxial and high isostatic pressing, and also sintering conditions, on the structure and properties of manganese—zinc, nickel—zinc, and barium ferrites was studied using x-ray, Mossbauer, magnetic, and gravimetric methods of analysis. Isostatic pressing was shown to have a positive effect on the crystallite-porosity structure and specified magnetic properties of the materials investigated.     

Formation Characteristics of Calcium Ferrite in Low Silicon Sinter

 Influence of sintering temperature, basicity and MgO content on the formation characteristics of calcium ferrite in low silicon sinter of Baotou Iron and Steel Company was studied by means of mini-sintering test and mineralographic microscope analysis. In addition, the suitable sintering parameters such as temperature and basicity were explored. The results found that optimum temperature for the formation of calcium ferrite is 1280 ℃, the basicity of 25-28 is helpful to the development of acicular or columnar calcium ferrite, and MgO content in the low silicon sintering raw materials should be lower than 28% because MgO can intensively inhibit the formation of calcium ferrite. And calcium ferrite in the sinter belongs to calcium ferrite with low calcium, which is different from that in ordinary sinter at home and abroad. So, it provided theoretical basis for promoting formation of calcium ferrite in low silicon sinter and improving properties of sinter.     

Potential of the High-Energy Hot Compaction in a Vacuum for Creating Materials with an Ultrafine Structure and High Strength

The typical form of specimens prepared by high-energy hot pressing in a vacuum using different deformation schemes and also the results of studying compaction, structure formation, and the physicomechanical properties of different materials in relation to billet heating temperature are presented. The structure and properties of specimens prepared by vacuum sintering are given for comparison. The efficiency of high-energy pressing of single-phase materials (nickel and molybdenum) and two-phase composites (dispersion-strengthened nickel Ni NiO and WC Co hard alloys) is demonstrated. The method makes it possible to prepare compact billets at quite low temperatures that provides retention of a fine-grained structure within them. As a result of this the materials have high mechanical properties that exceed those of specimens prepared by traditional methods.     

Structure,Properties, and Oxidation Resistance of Prospective HfB2–SiC Based Ceramics

Russian Journal of Non-Ferrous Metals - This work is devoted to the fabrication of heterophase powdered and sintered ceramics based on the hafnium diboride and silicon carbide by means of...     

高硅球团返矿高碱度烧结矿的冶金性能研究

高硅球团返矿高碱度烧结矿矿物组成及显微结构表明，显微结构对烧结矿的强度及冶金性能影响最大，发展针状铁酸钙的网状交织结构有利于提高烧结矿的质量。     

新一代新能源车驱动电机的高强硅钢应用技术研发

阐述了电驱动汽车所用电机的特点以及对硅钢的需求标准,并通过实验对比分析了高屈服强度无取向硅钢和传统无取向硅钢的电磁性能以及力学性能,通过有限元模型验证分析应用了高屈服强度硅钢的电机在高转速时可以达到低损耗、高机械强度等需求,为软磁材料的应用与电机结构的优化形成闭环模式提供了帮助。     

The preparation and some properties of materials on the base of silicon carbide with boron and aluminum additions

Summary An investigation was conducted on the modes of sintering samples of silicon carbide with additions of boron and aluminum by hot pressing, and some physical properties of the resulting alloys were studied.     

The reaction of vanadium,niobium, and tantalum diborides with carbon

Summary Using the methods of thermal, metallographic, and x-ray diffraction analyses, it was shown that the systems vanadium diboride-carbon,niobium diboride-carbon and tantalum diboride-carbon are pseudo-binary and eutectic. The eutectic temperatures and compositions were determined. When parts from vanadium, niobium, or tantalum diboride powders are produced by compaction in graphite molds, the pressing temperature must not exceed 2500–2600°K.     

Mechanical properties of molybdenum disilicide based materials consolidated by hot isostatic pressing (HIP)

The influence of hot isostatic pressing (HIP) consolidation parameters on the mechanical properties of molybdenum disilicide (MoSi₂) reinforced with ductile and brittle reinforcements was studied. MoSi₂, MoSi₂-20 vol.% coarse and fine niobium powder and MoSi₂-20 vol.% silicon carbide whiskers consolidation by HIP at 1200–1400°C, 207 MPa, for 1 and 4 h were tested in compression for elevated temperature strength and creep resistance. Single-edge-notched specimens of the three materials were tested in a three-point bend configuration for fracture toughness. Mechanical properties were related with consolidation parameters and post-HIP microstructures.     

Sintering of alloys of zirconium diboride with molybdenum disilicide

Summary The sintering of zirconium diboride with molybdenum disilicide is accompanied by the formation of a solid solution based on zirconium diboride, formation of a liquid phase at temperatures above 1800°C, and partial vaporization of silicon in the ZrB₂+15% MoSi₂ alloy. At temperatures up to 1800°C, solidphase sintering takes place; at low temperatures, this is accompanied by specimen growth due to heterodiffusion processes resulting from the difference in the partial diffusion coefficients of the components and to the vaporization of excess silicon in the case of the ZrB₂+15% MoSi₂ alloy.At temperatures above 1800°C, shrinkage is caused by the formation of a liquid phase, which disappears during sintering. Under these conditions, grain recrystallization and growth in the solid solution of Mo and Si in zirconium diboride in the case of 15% MoSi₂ alloys are not completed even after 4-h holding at temperatures of 1800, 1900, and 2000°C.Translated from Poroshkovaya Metallurgiya, No. 9(45), pp. 11–16, September, 1966.     

Recrystallization of silicon nitride powders during hot pressing

Conclusions The hot pressing of comminuted silicon nitride powders enables a uniform fine-grained structure of one and the same mean grain size to be obtained irrespective of the type of starting Si₃N₄, powder. At milling times of more than 100 h no significant decrease in particle size is observed. The recrystallization of milled silicon nitride powders during hot pressing takes place chiefly in the fine fractions appearing during milling. The degree of recrystallization attained is higher with ultrafine active silicon nitride powders (PCS) than with comminuted powders.Translated from Poroshkovaya Metallurgiya, No. 10(238), pp. 43–47, October, 1982.     

热压加工对含铬、镍块体纳米晶Fe_3Al组织和性能的影响研究

对通过铝热反应熔化制备的含10%(质量分数,下同)的铬和10%镍的块体纳米晶Fe3Al材料在不同温度、不同次数下进行了热压加工。利用XRD研究了热压加工前后纳米晶粒尺寸的变化,并测试了硬度变化和压缩率。结果显示:含10%铬的纳米晶Fe3Al在600℃表现出较好的塑性变形能力,材料在热压加工前后都是由无序bcc结构的Fe3Al相组成;含10%镍的纳米晶Fe3Al在800和1 000℃表现出较好的塑性变形能力,材料在热压加工前为无序bcc结构的Fe3Al相,在1 000℃热加工后,已转变为DO3有序结构;两种材料的压缩率都随着热压加工次数的增加逐渐增大。含10%铬的纳米晶Fe3Al在600℃和含10%镍的纳米晶Fe3Al在1 000℃随着热压加工次数的增加,晶粒尺寸都发生了增大,但材料硬度变化不大。     

Study of anisotropy in the properties of material prepared of powdered iron

We have used mathematical modeling with experimental verification of the results to study anisotropy in the properties of materials prepared of powdered iron. In fabrication of the powdered material, anisotropy arises in the structure as a result of the characteristic features of the technology, which affects the options for using the material. We have experimentally studied the degree of anisotropy in materials fabricated from powdered iron with different pressing forces. We propose mathematical models for the macrostructure of the powdered material, and test their adequacy to experimental data. We conclude that the degree of anisotropy in the powder material increases as it is compacted by increased pressing force. The structure of the material at the mesoscopic level after sintering can be considered as transverse isotropic, while the properties (depending on the degree of compaction of the material) can be described by a hexagonal or cubic symmetry system. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 88–97, March–April, 2006.