Utilization of NbC Nanoparticles Obtained by Reactive Milling in Production of Alumina Niobium Carbide Nanocomposites (original) (raw)
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Sintering behaviour of alumina–niobium carbide composites
Journal of The European Ceramic Society, 2000
Ceramic cutting tools have been developed as a technological alternative to cemented carbides in order to improve cutting speeds and productivity. Al2O3 reinforced with refractory carbides improve fracture toughness and hardness to values appropriate for cutting applications. Al2O3–NbC composites were either pressureless sintered or hot-pressed without sintering additives. NbC contents ranged from 5 to 30 wt%. Particle dispersion limited the grain growth of Al2O3 as a result of the pinning effect. Pressureless sintering resulted in hardness values of approximately 13 GPa and fracture toughness around 3.6 MPa m1/2. Hot-pressing improved both hardness and fracture toughness of the material to 19.7 GPa and 4.5 MPa m1/2, respectively.
Influence of NbC Content on the Wear Resistance of Alumina/Niobium Carbide Tools
2021
Wear resistance is a fundamental property which defines the lifetime of cutting tools, but the investigation of wear performance of alternative hard materials for traditional WC-Co composites are recent. The present work evaluated the pin-on-disk wear behavior and mechanical properties, i.e., hardness and fracture toughness of spark plasma sintered Al2O3 matrix composites with additions of 5, 15, 25 or 30%wt of niobium carbide NbC. The wear resistance was observed to increase as a function of the NbC content, even though the hardness reached a plateau at 25%wt NbC. The composite behavior was compared to that of other alumina composite tool materials proving to be a promising material for applications such as ceramic cutting tools. The composition A95N5 presented the best combination of values of wear rate: 8.9 mm3/N.m, hardness equal to (17.36±1.72) GPa and fracture toughness of (3.2±0.6) MPa. m1/2.
Synthesis of Al2O3–NbC by reactive milling and production of nanocomposites
Journal of Materials Processing Technology, 2003
Reactive high-energy milling can lead to self-sustaining reactions in the synthesis of a variety of systems, with the reaction being observed after an induction or ignition time which produces a temperature increase in the reactants. The products of such reactions are usually very strong agglomerates which, would be not very useful for further processing; to obtain fully dense sintered samples, it would be necessary an additional and difficult desagglomeration procedure. Therefore, the knowledge and control of the mechanism during reactive high-energy milling may be important in preventing or reducing this agglomeration and improve the physical properties of the powder reaction products. In the present work, high-energy ball milling of the powder mixture Nb 2 O 5-Al-C was performed in a SPEX 8000 shaker/mill. The reaction was monitored by a thermocouple fixed in the external surface of the vial. With the condition of ball to mass ratio of 4:1 ignition occurs after 190 min milling. Powder mixtures were characterized after different milling times before and after the reaction. Also, alumina powder was added as diluent to the reactant mixture aiming to decrease the reaction temperature. The powders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The reaction products after 1 h were desagglomerated and mixed with commercial ultra-fine alumina powder, producing alumina matrix nanocomposites with 5 wt.% of NbC.
Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling
Metallurgical and Materials Transactions B, 2017
Aluminum and its alloys are key materials for the transportation industry as they contribute to the development of lightweight structures. The dispersion of hard ceramic particles in the Al soft matrix can lead to a substantial strengthening effect, resulting in composite materials exhibiting interesting mechanical properties and inspiring their technological use in sectors like the automotive and aerospace industries. Powder metallurgy techniques are attractive to design metal matrix composites, achieving a homogeneous distribution of the reinforcement into the metal matrix. In this work, pure aluminum has been reinforced with particles of niobium carbide (NbC), an extremely hard and stable refractory ceramic. Its use as a reinforcing phase in metal matrix composites has not been deeply explored. Composite powders produced after different milling times, with 10 and 20 vol pct of NbC were produced by high-energy ball milling and characterized by scanning electron microscopy and by X-ray diffraction to establish a relationship between the milling time and size, morphology, and distribution of the particles in the composite powder. Subsequently, an Al/10 pct NbC composite powder was hot extruded into cylindrical bars. The strength of the obtained composite bars is comparable to the commercial high-strength, aeronautical-grade aluminum alloys.
Ceramics International, 2014
Alumina-based composite ceramic tool materials reinforced with carbide particles were fabricated by the hot-pressing technology. Choice of metallic phase added into the present composite ceramic was based on the distribution of residual stress in the composite. The effects of metallic phase on microstructure and mechanical properties of composites were investigated. The metallic phase could dramatically improve room temperature mechanical properties by refining microstructure, filling pores and enhancing interfacial bonding strength. However, it also led to sharp strength degradation at high temperature because the metallic phase was easier to be oxidized and get soft at high temperature in air. The effects of metallic phase on strengthening and toughening were discussed. The improved fracture toughness of composite with metallic phase was attributed to the lower residual tensile stress in the matrix and the interaction of more effective energy consuming mechanisms, such as crack bridged by particle, crack deflection and intragranular grain failure.
Production of copper–niobium carbide nanocomposite powders via mechanical alloying
Materials Science and Engineering: A, 2005
Nanocrystalline niobium carbide was synthesed in situ in a copper matrix during high-energy milling of elemental powders. Three powder batches were produced with nominal compositions of 5, 10 and 20 vol.% NbC. Characterisation by X-ray diffraction and scanning electron microscopy indicates that early during the milling process a carbide dispersion is formed within a nanostructured copper matrix. After annealing at 873 K, the carbide structure and particle size are maintained, reflecting the ability of the microstructure to resist to coarsening. The hardness levels attained are more than twice those of nanostructured copper.
Surface characterization of alumina reinforced with niobium carbide obtained by polymer precursor
Materials Research, 2006
Active filler controlled pyrolysis of polymers (AFCOP) is a recent method for obtaining near-net shaped ceramic bodies. Alumina based composites have been developed for use as cutting tools, so knowledge of the surface composition is extremely important because it is directly related to the hardness and wear resistance Samples containing a fixed concentration of 60 wt. (%) of polysiloxane and a mixture of metallic niobium and alumina powder were homogenized, uniaxially warm pressed at 80 °C and subsequently pyrolyzed in flowing argon at 1200, 1400 and 1500 °C. Analysis of the surface composition was carried out by X ray photoelectron spectroscopy, infrared spectroscopy, X ray diffraction and scanning electron microscopy. The results have indicated that the formation of the phases on the surface depends strongly on the niobium/carbon ratio in the raw materials.
Properties of sintered alumina reinforced with niobium carbide
International Journal of Refractory Metals and Hard Materials, 2009
The presence of carbide or nitride particles in Al 2 O 3 -based composites may produce a pinning effect and inhibit the grain growth of the matrix, which might significantly contribute to the final performance of the composite. Fracture toughness, mechanical strength and wear resistance have been particularly improved by the dispersion of hard particles. This work has the purpose to investigate the potential use of NbC as alumina reinforcing material, as an alternative to other carbides such as TiC, WC and (W, Ti)C. Alumina was mixed with a constant 30 wt.% of carbide in a ball mill, uniaxially hot-pressed at 1600°C and 20 MPa in an inert atmosphere, and characterized. X-ray diffraction revealed that alumina and the added carbide were the only crystalline phases present and no oxidation products were detected. The increase in fracture toughness likely is the result of crack deflection, triggered by carbide particles at the alumina grain boundaries. The results obtained in this work show that alumina reinforced with NbC is a composite material with properties comparable to those of alumina reinforced with WC, TiC or (W, Ti)C, making NbC a good reinforcing material.
Ceramics International, 2001
Alumina-based composites reinforced with refractory carbides are potential cutting tool materials. They exceed the capabilities of cemented carbides with respect to hot hardness and thermal stability, resulting in faster cutting speeds. Liquid-phase sintering of Al2O3–NbC composites was investigated as an alternative to pressure-assisted processes. Al2O3 reinforced by NbC (5–40 wt.%) was sintered with 3 wt.% Y2O3. In order to assess the effect of the formation of a liquid phase on the properties of the composites, sintering was carried out either below or above the Al2O3–Y2O3 eutectic temperature, at 1650 and 1800°C, respectively. Density, hardness, fracture toughness and wear resistance of the composite materials were evaluated. Liquid phase sintering did not affect the fracture toughness, but improved both the density and the hardness of the material, regardless of its NbC contents. Higher concentrations of NbC increased the wear resistance of the composite.