Papers by Keyword: Cermet

Abstract: This research synthesized a composite ceramic material base CaCO₃/Al₂O₃, CERMET, with possible biomedical applications. Eggshell was used as raw material to obtain CaCO_3, and it was reinforced with silver nanoparticles to improve the structural and mechanical properties of the ceramic system. The addition of silver nanoparticles promotes the formation of two phases. The first is a continuous phase called a matrix formed of CaAl₂O₄ (calcium aluminate). The second is a dispersed phase known as reinforcement made up of silver nanoparticles. The composite ceramics were synthesized using the solid-state synthesis technique from a chemical mixture of CaCO₃ and Al₂O₃ powders in the following chemical ratio: 49.5% CaCO₃ + 50.5% Al₂O₃, with silver nanoparticles added at different percentages (1%, 5%, 10%, 15%). The powder mixture was made in a high-energy mill for homogenization. After that, the mixture was compressed into cylindrical samples for their consolidation by sintering in a high-temperature muffle with a controlled atmosphere, using heating ramps. The sintered samples were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, and microhardness, including fracture toughness studies. In addition, the Archimedes method determined the sintered samples' density. The results showed a clear relation between the mechanical properties of the CaAl₂O₄ ceramic base and the incorporated silver nanoparticles since these increased as the percentage of silver nanoparticles increased. In addition, it was observed that the porosity of the samples could be controlled, making the composite material suitable for biomedical applications.

Abstract: This study analyzes the thermomechanical behavior of SiC/Si/TiSi₂ cermets manufactured from Peruvian wood waste of the Capirona and Capinuri species. A sustainable manufacturing process was used that uses sawdust as a precursor. The mechanical properties under compression and the elastic modulus of the cermets were characterized from room temperature to 1400°C. At room temperature, the values achieved exceed 500 MPa in both cermets, with the Capinuri precursor being slightly higher in maximum compressive strength with 691 MPa, but in elastic modulus, the Capirona cermet has a rigidity of 159 GPa. At 500°C, the cermets showed a small reduction in their mechanical performance. At 1100°C, a decrease in strength was observed to 248 MPa for Capinuri and 292 MPa for Capirona and in Young's modulus to 85.18 GPa and 91.92 GPa respectively. At 1400°C, both cermets suffered a significant deterioration of their mechanical properties due to a presumed chemical degradation of the individual components. The results demonstrate the feasibility of using wood waste as precursors for the sustainable manufacturing of advanced composite materials, however, optimization of manufacturing parameters and processes should be considered to improve the performance and stability of this material.

Abstract: On the one hand, cermet has the advantages of metal materials, and on the other hand, it maintains the excellent properties of ceramic materials, and is a very important new engineering material. In this paper, the alumina/aluminum cermet material composite powder was prepared by ball milling, and its densification properties were characterized and studied to provide reference for the preparation of high-performance cermet materials. When the ball milling time is more than 6h, the distribution of alumina particles around the aluminum powder is relatively uniform. The research shows that: with the extension of the ball milling time, the number of pinning of Al₂O₃ particles on the surface of the Al ball first increases and then decreases; The trend of decreasing; with the increase of ball-to-powder ratio, the distribution of Al₂O₃ particles on the surface of Al balls is more uniform. Considering its cost-effectiveness, it is more suitable to prepare pinned alumina/aluminum-ceramic composite powder under the conditions of ball milling speed of 360r/min, ball-to-material ratio of 2:1 and ball milling time of 12h. When the Al content gradually decreased, the density and hardness of the cermet material also decreased gradually. When the Al content gradually decreased, the density and hardness of the cermet material also decreased gradually. When Al accounts for 75% in the sample, the microstructure is dense and the hardness is higher. When the molding pressure is 20MPa, the unevenness of the surface of the material is greatly relieved, relatively flat, and the densification effect is better. When the sintering temperature is 800°C, the fired sample is very dense, and the particles have relatively high bonding strength, but a small amount of aluminum is precipitated on the surface of the sample, forming a silver-white spherical substance.

Abstract: Plasma transfer arc welding (PTAW) has been one of the popular methods for depositing thick hard facing. In this study, this method was used to lay the nickel hard-facing without tungsten carbide and with different compositions which are 35 wt%, 50 wt% and 60 wt% carbides. The hard facing was characterised using a scanning electron microscope with EDS and x-ray diffractometer (XRD). The corrosion behaviour was evaluated using three electrodes electrochemical test with saturated calmonel electrode (SCE) and platinum plate as the reference electrode and counter electrode respectively. The corrosion test shows that the hard facing had higher corrosion resistance in an alkaline environment compared to an acidic environment. The corrosion mechanism was by the dissolution of the nickel matrix, Ni₃B dissolution is seen in an acidic environment while in alkaline electrolyte, the dendritic nickel dissolves preferentially.

Abstract: Pure niobium substrates were coated using laser cladding method. Pure molybdenum, Yttria Stabilized Zirkonia (YSZ) and corundum (Al₂O₃) powders were used as coating materials. Coatings were deposited on specimens as seperate paths with 3÷10mm width and 40mm of length. Two different laser power 3kW and 4kW were tested during deposition. In order to assess the quality of the Mo-YSZ and Mo-Al₂O₃ coatings, the light microscopy, Scanning Electron Microscopy (SEM), chemical analysis (EDS) and Vickers hardness test investigation were performed. The surface roughness and wear volume were also measured. As a result of YSZ-Mo powder cladding on the Nb substrate the composite layers were obtained without cracks and porosity not exceeding 1 μm. In addition, an increase in hardness of about 450 HV0.5 was revealed. As a result of Al₂O₃-Mo powder cladding on the Nb substrate the composite layers with many voids and cracks were obtained for each of the cladding variants.

Abstract: Friction stir welding (FSW) is employed primarily for metals characterized by poor weldability at fusion welding: aluminium, magnesium, titanium and copper alloys as well as stainless steels. The focus of the study was on the feasibility of application of WC-based hardmetal 85WC-Co and TiC-based cermet 80TiC-NiMo as potential tool materials for FSW of copper. The single-pass welding trials of Cu sheets were performed using a vertical milling machine. For better understanding of interactions between the tool and workpiece at welding temperature EDS line scans across the interfaces tool-workpiece after welding as well as after diffusion tests were performed. It was concluded that both tested ceramic-metal composites did not failure during multiple plunges and during the total transverse welding distance of 10 m. Also, significant tool wear was not observed after such a welding distance. The possibility of producing visually defect-free welds using tools from WC- and TiC- based ceramic-metal composites was proved and also mutual diffusion of elements across the interface tool-workpiece was discussed.

Abstract: In this paper, the effect on the properties of alumina/aluminum cermet by changing the sintering temperature, and comparing the advantages and disadvantages of different characterization methods and their application range, it provides a reference for selecting the characterization technology suitable for alumina/aluminum composites.Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn: the higher the vacuum sintering temperature, the more aluminum material is melted out of the body to form aluminum balls on the surface, and the green body The more severe the cracking. When the sample is sintered at a temperature of 600 °C, the density is the highest and the appearance is the best. When the molding pressure is 40 MPa and the sintering temperature is 700 °C, the microstructure of the sintered alumina/aluminum cermet is better. It can be seen from SEM and EDS analysis that the particles are continuously distributed and the larger one is metal Al, and the particles are discontinuously distributed and finer is Al₂O₃.

Abstract: In this paper, the effect of raw materaisl on the properties of coated Al₂O₃/Al cermet materials were investigated, the raw materials were prepared via different methods, which provide a reference for obtaining higher performance cermet materials. Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn, the density of the cermet material prepared by the mechanical ball milling method (83.5%) is higher than that of the cermet material prepared by the chemical precipitation method (92.8%). It is nearly 10% lower. The alumina particles prepared by the ball milling method are agglomerated, and a large amount of agglomeration occurs in the aluminum, and the composition is very uneven. For materials prepared by the precipitation method, the aluminum oxide is uniformly distributed in the aluminum. The ball-milling powder is used to prepare materials, most of the alumina is in the form of particles, and in the precipitation method. In the powder preparation sample, the thin layer of alumina which forms the same eggshell envelops the aluminum, and the aluminum has a certain liquid phase change. the surface hardness (824HV) of the cermet material prepared by the mechanical ball milling method is lower than the surface hardness (1005HV) of the cermet material prepared by the chemical precipitation method.

Abstract: The article is devoted to the study of the characteristics of shock-wave processing of powder mixtures capable of an exothermic reaction of the synthesis of metal-ceramic materials. Experiments on shock-wave initiation of synthesis in systems based on Ti-B and Ti-C with 10% and 20% Ni content were carried out. Explosive loading was carried out by oblique throwing of a steel drummer with speeds of 1000 m / s and 1500 m / s. X-ray phase analysis of synthesis products showed the presence of TiB₂ diboride and TiC carbide in the nickel bond. The significant role of the mechanical activation of powder mixtures in increasing the sensitivity of SHS-mixtures to shock-wave loading is shown.

Abstract: 3D printing of plastic materials is very popular nowadays, while printing of wear resistant hard materials is still an issue. Gradient or functionally graded structures are providing improved performance in impact-abrasive application (tunnelling, geothermal drilling, mining, etc.) through the optimal positioning of areas providing high wear resistance and high resistance against impacts. However, printing of such structures by widely used powder bed selective laser sintering leads to the high consumption of raw materials (powders) that cannot be used again for next printing. A method to overcome this problem is explored in current work. The cermets were produced from following powders: (1) commercial, (2) obtained by disintegration of cutting tool inserts (recycled) and (3) reused recycled ones. Tungsten and cobalt used for the production of the majority of cermets are critical raw materials and their consumption should be reduced while the rate of recycling needs to be increased. The surfaces were studied with the help of optical microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The hardness and wear rate of samples in abrasive conditions were measured.