电弧喷涂含陶瓷颗粒铝基复合涂层的微结构和性能

采用5052半硬铝带分别包覆Al_2O_3、SiC、B_4C、TiC陶瓷颗粒制备的粉芯丝材进行电弧喷涂试验,制备了含陶瓷颗粒的铝基复合涂层。利用光学显微镜、XRD分析了涂层的微观组织和相结构,测试了复合涂层的显微硬度、耐磨性及耐腐蚀性。研究结果表明,制备的铝基复合涂层中含有一定数量的未熔陶瓷颗粒,涂层较为致密,无明显缺陷。含陶瓷铝基涂层的物相主要由Al和所添加的陶瓷相构成,其中在含B_4C陶瓷涂层中还存在Al_3BC、Al_4C_3和AlB_2等新相。陶瓷颗粒的加入有利于提高铝基复合涂层的显微硬度,其中B_4C的加入使涂层中基体相显微硬度提高了1.5倍,这是由于B_4C陶瓷和Al反应生成Al_3BC、Al_4C_3和AlB_2硬质相。复合涂层的耐磨性均优于纯铝涂层,摩擦磨损的形式主要为粘着磨损。动电位极化腐蚀试验表明,含SiC和TiC陶瓷涂层具有较低的腐蚀电流,耐蚀性较好,含SiC陶瓷的复合涂层出现了明显的钝化现象。     

Phase diagram of the Al2O3-ZrO2-Er2O3 system. II. Phase diagram liqiudus surface

The liquidus surface for the Al₂O₃-ZrO₂-Er₂O₃ phase diagram is projected for the first time onto a concentration triangle. No ternary compounds are found in the system. The liquidus surface is completed by eight primary crystallization fields. Four four-phase nonvariant eutectic equilibria, one four-phase nonvariant transformation equilibrium, and three three-phase nonvariant eutectic equilibria are found in the system. Since ZrO₂ interacts with other phases eutectically, the unique properties of ZrO₂-based T-and F-solid solutions can be combined with the properties of other phases of the ternary system in composite materials. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 64–71, 2007.     

Fusion and Dispersion of Oxide Materials in a “Cold” Crucible and in Furnaces with Concentrated Radiant Heating

Melting and dispersion of oxide materials in the system ZrO₂ - HfO₂ - Y₂O₃ is carried out in furnaces with concentrated radiant and induction heating. The polyfractional powders obtained are stabilized solid solutions of the fluorite type. A reduction is established for elementary cell parameters (from 0.5144 to 0.5127 nm) for specimens whose composition relates to an isoconcentrate with 10 mole% Y₂O₃ with an increase in HfO₂ content. Melted and dispersed ZrO₂ - HfO₂ - Y₂O₃ materials are promising for creating dense and highly refractory ceramic materials. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 36–42, July–August, 2005.     

Microstructure and properties of Al2O3-Al(Si) and Al2O3-Al(Si)-Si composites formed byin situ reaction of Al with aluminosilicate ceramics

Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites have been formed byin situ reaction of molten Al with aluminosilicate ceramics. This reactive metal penetration (RMP) process is driven by a strongly negative Gibbs energy for reaction. In the Al/mullite system, Al reduces mullite to produce α-Al₂O₃ and elemental Si. With excess Al (i.e., x > 0), a composite of α-Al₂O₃, Al(Si) alloy, and Si can be formed. Ceramic-metal composites containing up to 30 vol pct Al(Si) were prepared by reacting molten Al with dense, aluminosilicate ceramic preforms or by reactively hot pressing Al and mullite powder mixtures. Both reactive metal-forming techniques produce ceramic composite bodies consisting of a fine-grained alumina skeleton with an interpenetrating Al(Si) metal phase. The rigid alumina ceramic skeletal structure dominates composite physical properties such as the Young’s modulus, hardness, and the coefficient of thermal expansion, while the interpenetrating ductile Al(Si) metal phase contributes to composite fracture toughness. Microstructural analysis of composite fracture surfaces shows evidence of ductile metal failure of Al(Si) ligaments. Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites produced byin situ reaction of aluminum with mullite have improved mechanical properties and increased stiffness relative to dense mullite, and composite fracture toughness increases with increasing Al(Si) content. This article is based on a presentation made in the “In Situ Reactions for Synthesis of Composites, Ceramics, and Intermetallics” symposium, held February 12–16, 1995, at the TMS Annual Meeting in Las Vegas, Nevada, under the auspices of SMD and ASM-MSD (the ASM/TMS Composites and TMS Powder Materials Committees).     

Effect of melt cleanliness on the properties

An experimental study was conducted to examine the effect of melt cleanliness with respect to the presence of inclusions on the properties of an Al-10 wt pct Si metal matrix composite (MMC) reinforced with 10 vol pct SiC particles. The occurrence of inclusions was controlled by filtra- tion, using ceramic foam filters of 10, 20, and 30 ppi sizes, under gravity and pressure. Test bars obtained from filtered and unfiltered melt castings, prepared from fresh (as-received) and recycled composite materials, were T6-tempered and tensile tested at room temperature. The casting quality was examined using X-ray radiography. The results indicate that various factors influence the casting quality and mechanical properties of the cast composite. The A1₂O₃ films and spinel MgAl₂O₄ — the main inclusions observed in the present composite — are chiefly responsible for the degradation in the mechanical properties. In addition, SiC sedimentation, Al₄C₃ formation, the hydrogen level of the melt, and the starting material used can also influence these properties. Fracture studies reveal that the inclusions and associated microvoids act as the crack initiation sites during composite fracture. Simple filtration using 10 ppi ceramic foam filters under gravity serves adequately in removing these inclusions and producing the desired mechanical properties.     

Phase diagram of the Al2O3-ZrO2-Sm2O3 system. II. Liquidus surface

A projection has been constructed for the liquidus surface on the plane of the concentration triangle for the Al₂O₃-ZrO₂-Sm₂O₃ phase diagram. There are no ternary compounds, or appreciable regions of solid solutions based on the components and the binary compounds. The liquidus surface is formed by nine fields of primary phase crystallization. There are five four-phase nonvariant peritectic equilibria, as well as two four-phase nonvariant eutectic equilibria, and one three-phase nonvariant eutectic equilibrium. As the ZrO₂ and SmAlO₃ phases interact with other phases by a eutectic mechanism, it is possible to combine the unique properties of the T and F solid solutions based on ZrO₂ with the properties of the other phases in the form of composites. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 28–35, March–April, 2006.     

Influence of the Composition and Structure of B4C - Al2O3 Ceramic on the Tribotechnical Characteristics in Friction Against Steel

The morphology and phase composition of friction surfaces and the tribotechnical properties of the (B₄C - Al₂O₃)-steel 45 system are studied under dry friction at various sliding velocities and contact loads. We have found that fine-grained secondary structures are formed on the friction surfaces. The morphology and phase composition of these structures depend on the ceramic composition and on the test conditions. A comprehensive investigation of friction surfaces, using x-ray, electron-diffraction electron-probe, and electron-microscopy analysis, has shown that the structure and morphology of the secondary phases determine the tribotechnical properties of ceramic-steel couples. The maximum wear resistance of B₄C ceramics containing 5-20 mass% Al₂O₃ is determined by the formation of dense secondary-phase thin films on the friction surface. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 49–59, May–June, 2005.     

Thermal Shock Resistance of Al2 O3/ZrO2 (Y2O3) Composites

ZrO₂ containing 2% (mol fraction) Y₂O₃ and 3% (mol fraction) Y₂O₃ were added into Al₂O₃ matrix, compositing composites with 15% volume fraction of addictives mentioned above. The testing of property and analysis of SEM presented that, after vacuum sintering at 1550 °C, thermal shock resistance of two composites was superior to Al₂O₃ ceramic. The experiment showed that the properties of Al₂O₃ composites was higher than Al₂O₃ ceramic, and Al₂O₃/ZrO₂(3Y) was higher than Al₂O₃/ZrO₂(2Y) in thermal shock resistance. Improvement of thermal shock resistance of composites was attributed to many toughness machanisms of ZrO₂(Y₂O₃). By calculation, the fracture energy of Al₂O₃, Al₂O₃/ZrO₂ (2Y) and Al₂O₃/ZrO₂(3Y) was 38100.8 and 126.2 J·m⁻², respectively. Cracks initiation resistance (R') of Al₂O₃/ZrO₂(3Y) and Al₂O₃/ZrO₂(2Y) was higher than Al₂O₃ ceramic by 1.57 and 1.41 time, respectively, and cracks propagation resistance (R″″) was higher than Al₂O₃ ceramic by 1.46 and 1.38 time, respectively, which was corresponding to the results of residual strength.     

Microstructure of bonding zones in laser-clad Ni-alloy-based composite coatings reinforced with various ceramic powders

Microstructure of the bonding zones (BZs) between laser-clad Ni-alloy-based composite coatings and steel substrates was studied by means of scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. Observations indicate that for pure Ni-alloy coating the laser parameters selected for good interface fusion have no effect on the microstructure of the BZ except for its thickness. However, the addition of ceramic particles (TiN, SiC, or ZrO₂) to the Ni alloy varies the compositional or constitutional undercooling of the melt near the solid/liquid interface and consequently leads to the observed changes of microstructure of the BZs. For TiN/Ni-alloy coating the morphology of y-Ni solid solution in the BZ changes from dendritic to planar form with increas-ing scanning speed. A colony structure of eutectic is found in the BZ of SiC/Ni-alloy coating in which complete dissolution of SiC particles takes place during laser cladding. The immiscible melting of ZrO₂ and Ni-alloy powders induces the stratification of ZrO₂/Ni-alloy coating which consists of a pure ZrO₂ layer in the upper region and a BZ composed mainly of y-Ni dendrites adjacent to the substrate. All the BZs studied in this investigation have good metallurgical characteristics between the coatings and the substrates.     

Fabrication of Al2O3-reinforced Ni3Al composites by a novel in situ route

A novel in situ technique has been used to fabricate an Al₂O₃-reinforced Ni₃Al matrix composite. The composite was prepared by first incorporating a low volume fraction of continuous Al₂O₃ fibers in a Ni₃Al alloy containing 0.34 at. pct Zr. Pressure casting was used to embed the fibers. Casting resulted in partial reduction of the Al₂O₃ fiber by the Zr present in the matrix and the formation of a layer of ZrO₂ on the surface of the fibers. The final composite was then prepared by air annealing the precursor composite at 1100 °C for 10 days. Air annealing led to the formation of networks of Al₂O₃ around the fibers. The matrix in the immediate vicinity of the networks consisted of Ni₃Al particles in a matrix of disordered α-Ni(Al). The Al₂O₃ networks raised the yield and tensile strength of the material by 35 and 18 pct, respectively. The composite had a tensile ductility of 14 pct.     

Reinforcing Mechanism of Mg‐PSZ Particles in Highly‐Alloyed TRIP Steel

Dense TRIP‐matrix composites containing 5 vol.% Mg‐PSZ as reinforcing phase were produced by employing the spark plasma sintering technique. A continuous and seamless interface between the ceramic particles and the steel matrix was achieved. Compression tests revealed better mechanical properties of the 5 vol.% Mg‐PSZ‐TRIP steel composites in comparison with both, pure and Al₂O₃ reinforced TRIP steel. The underlying deformation mechanism within the austenitic matrix entailed a pronounced martensite formation. An additional phase transformation was observed within the ZrO₂ particles. The enhanced mechanical properties of the 5 vol.% Mg‐PSZ composite are dedicated to the transformation strengthening of the ceramic particles. Finally a model of the reinforcing mechanism is proposed.     

Riction properties of composite materials of the system TiN - Ain. II. Effect of oxide films on friction and wear of a ceramic material — Steel system

Friction and wear are studied for materials of the system TiN — AlN preliminary oxidized at 800–1100°C. It was established that thin oxide films containing Al₂TiO₅ and α-Al₂O₃, that promote a decrease in frictional wear, form on the surface of composite materials of the system TiN — AlN. Our assumptions are confirmed that the improvement in tribological properties of TiN — AlN composites is caused by forming oxide screening layers that prevent direct contact between the ceramics and steel counter-body. At high rates (V=16 m/sec) and pressure (P=2.0 MPa) the oxide films form more rapidly. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 121–124, January–February, 2000.     

Phase diagram of the Al2O3-ZrO2-Sm2O3 system. III. Solidus surface and phase equilibria in alloy crystallization

A projection has been constructed for the solidus surface in the Al₂O₃-ZrO₂-Sm₂O₃ phase diagram on the plane of the concentration triangle, which consists of seven isothermal three-phase fields corresponding to two nonvariant equilibria of eutectic type and five nonvariant equilibria of peritectic type, and also eight lineated surfaces for the end of crystallization of the binary eutectics. The highest temperature on the solidus surface is 2710°C, the melting point of pure ZrO₂, while the lowest is 1680°C, the temperature of the triple eutectic Al + F + SA. No ternary phases or appreciable regions of solid solutions based on the components and the binary compounds are observed. Data on the bounding binary systems, the liquidus and solidus surfaces have been used to construct the phase-equilibrium (melting) diagram together with a reaction scheme for the equilibrium crystallization of alloys in the Al₂O₃-ZrO₂-Sm₂O₃ system. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 56–64, May–June, 2006.     

Observation of calcium aluminate inclusions at interfaces between Ca-treated,Al-killed steels and slags

The evolution of Al₂O₃-CaO inclusions on molten steel surfaces and at molten steel/slag interfaces was observed in-situ through a confocal scanning laser microscope (CSLM) equipped with a gold-image furnace. Depending on the slag chemistry, some of the initially liquid inclusions evolved into irregular Al₂O₃ or SiO₂-enriched inclusions during the separation across the interface. Inclusions were found to cluster at specific locations at the steel/slag interface. Unlike capillary-depression-driven clustering, which is observed on molten steel surfaces, a weak repulsive force opposes fluid-flow-driven clustering at the steel/slag interface. After clustering, the irregular solid inclusions were observed to agglomerate to form large aggregates. This article is based on a presentation given in the Mills Symposium entitled “Metals, Slags, Glasses: High Temperature Properties & Phenomena,” which took place at The Institute of Materials in London, England, on August 22–23, 2002.     

The effect of dispersion hardening on the regularities and mechanisms of the creep of copper with submicron grain sizes

Regularities and mechanisms of the creep of submicrocrystalline copper and Cu-1.1 vol % Al₂O₃ dispersion-hardened powder composite in a temperature range of (0.2–0.35) T _{m Cu} have been investigated. The role that the grain-boundary state and dispersion-hardening material with Al₂O₃ nanosized (10–40 nm) particles plays in the development of plastic deformation during creep is analyzed.     

Composites with a functional gradient in the systems Si3N4−Al2O3−Y2O3−TiC

Composites with a functional gradient in the system Si₃N₄−Al₂O₃−Y₂O₃−TiC were made by laminating and sintering ceramic films obtained by tape casting. The films had high contents of TiC and Al₂O₃ and were of different thicknesses. Materials with a high density and high fracture toughness (K_1c≈9.3 MPa·m^1/2) were obtained. Warsaw Polytechnic Institute. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 1–7, July–August, 1999.     

Phase diagram of the ZrO2-Y2O3-Sm2O3 system in the melting-point region

A polynomial method has been used to construct a model for the liquidus surface in the ZrO₂-Y₂O₃-Sm₂O₃ phase diagram; that surface is made up of four fields of primary crystallization for the following phases: solid solutions based on cubic (C) and hexagonal (H) Y₂O₃, cubic ZrO₂ with a structure of fluorite type F, and high-temperature cubic La₂O₃ (X). The ternary system has two nonvariant four-phase equilibria of incongruent type. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(450), pp. 60–67, July–August, 2006.     

Making low-porosity materials with improved thermal resistance on the basis of corundum with added ZrO2, Si3N4, AlN, and SiO2

Added ZrO₂, Si₃N₄, AlN, and SiO₂ affect the consolidation of aluminum oxide on sintering in nitrogen, vacuum, and air, as well as affecting the thermal resistance of the materials. The relative density of material based on Al₂O₃ is largely dependent on the type and amount of additive, the component ratio, and the sintering medium. High density and thermal stability occur in materials formed by sintering in nitrogen from aluminum oxide containing ZrO₂, Si₃N₄ and SiO₂. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3-4(400), pp. 48–52, March–April, 1998.     

Al2O3/TiCN-0.2% Y2O3 Composite Prepared by HP and Its Cutting Performance

Al₂O₃/TiCN-0.2% Y₂O₃ composites were fabricated by hot pressing sintering. The effect on mechanical property and microstructure of the sample composition and HP temperate was investigated. The results of Al₂O₃/TiCN-0.2% Y₂O₃ were satisfied. The bending strength, fracture toughness, Vickers hardness was respectively 1015 MPa, 6.89 MPa·m^1/2 20.82 MPa at 1650 °C for 20 min. Good wear resistance was found for the kind of ceramic material when used as cutting tools in the machining of the hardened carbon steel. By the compared experiment for the cutting performances, it could be seen that the performance of this composite material was better than that of the ceramic tool material YT15 for continuously cutting quenched steel. This kind of composite tool material is suitable for continuously cutting quenched steel No.45, especially intermittently cutting quenched steel.     

New water-soluble acrylic bonding agents for shaping ceramic materials

Preliminary results are reported on the synthesis and use of new water-soluble polymer binders for making ceramic films from Al ₂O₃ by casting. The binders produce cast materials having high contents of the solid phase and with rheological properties that provide for good flow of the cast mass and for easy separation of the film from the substrate. The emulsions wet Al₂O₃ well, so one can make ceramic films with appropriate densities, elasticities, and mechanical strength in the raw state, and these can be fired to make planeparallel specimens free from cracks and having high density, good mechanical strength, and low roughness. Warsaw Polytechnic. Translated from Poroskhovaya Metallurgiya, Nos. 5–6(407), pp. 15–20, May–June, 1999.