Structure Formation in Ti-C-Ni-Mo Composites during Reactive Sintering (original) (raw)
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The formation of reactive sintered (Ti, Mo)C–Ni cermet from nanocrystalline powders
International Journal of Refractory Metals and Hard Materials, 2014
Titanium carbide based cermets with molybdenum as alloying element and nickel as binding metal were produced using high energy powder milling of elemental powders of Ti, Ni, Mo and C (carbon black) followed by liquid state sintering. Reactive sintering process was applied where the synthesis of (Ti, Mo)C occurs in solid state and the final densification of the cermet is achieved during liquid state. Reactive sintering allows to obtain uniform finegrained cermets and also to decrease the production costs of the cermets because it excludes the expensive very high temperature carbide synthesis. The phase and microstructure evolution is analysed by means of XRD, TGA and SEM equipment. Material properties are characterised by hardness and transverse rupture strength. Keywords; TiC base cermets; reactive sintering; microstructure evolution, mechanical properties. Highlights Reactive sintered (Ti, Mo)C-Ni cermets were produced. Carbide formation occurs in three steps. The final microstructure of the cermet has two phases. A two step sintering is required for reactive sintering.
International Journal of Refractory Metals and Hard Materials, 2005
In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powder metallurgy process. The titanium nitride (TiN) and titanium carbide (TiC) used as starting powders have been synthesized by the self-propagating high temperature synthesis (SHS) method. This exothermic reaction, easy to process, allows to obtain fine and original powders from lowcost raw materials. Cermets obtained by sintering powders of TiC and Mo 2 C with nickel binder phase are investigated. The effect of TiN adding on the microstructure and the mechanical properties of these composites are studied. Microstructures have been observed by scanning electron microscopy (SEM). Room temperature mechanical properties such as YoungÕs modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribological experiments were also performed and the friction coefficient of a cermet containing titanium nitride was compared with that of other hard materials. The SHS starting powders used present some particularities, as it was shown in a previous study [Matériaux à base de carbures et nitrures, pour coupe et usure, obtenus à partir de poudre SHS, PhD Thesis, INSA Lyon, 2004]. The purpose of this work is to show that results concerning the impact of TiN addition on microstructure and mechanical properties obtained on bulk specimens, from these original starting powders, are similar to the ones obtained on alloys from commercial starting powders.
Sintering Behavior and Microstructure of TiC-Me Composite Powder Prepared by SHS
Metals, 2017
Titanium, its alloys, and refractory compounds are often used in the compositions of surfacing materials. In particular, under the conditions of electron-beam surfacing the use of synthesized composite powder based on titanium carbide with a metal binder (TiC-Me) has a positive effect. These powders have been prepared via the self-propagating high-temperature synthesis (SHS) present in a thermally-inert metal binder. The initial carbide particle distribution changes slightly in the surfacing layer in the high-energy rapid process of electron-beam surfacing. However, these methods also have their limitations. The development of technologies and equipment using low-energy sources is assumed. In this case, the question of the structure formation of composite materials based on titanium carbide remains open, if a low-energy and prolonged impact in additive manufacturing will be used. This work reports the investigation of the sintered powders that were previously synthesized by the layerwise combustion mode of a mixture of titanium, carbon black, and metal binders of various types. The problems of structure formation during vacuum sintering of multi-component powder materials obtained as a result of SHS are considered. The microstructure and dependences of the sintered composites densification on the sintering temperature and the composition of the SH-synthesized powder used are presented. It has been shown that under the conditions of the nonstoichiometric synthesized titanium carbide during subsequently vacuum sintering an additional alloy formation occurs that can lead to a consolidation (shrinkage) or volumetric growth of sintered TiC-Me composite depending on the type of metal matrix used.
Ti-Mo-xTiC composites manufactured by U-FAST reactive sintering
The paper presents the characteristics of Ti-Mo-xTiC composites manufactured under experimentally selected conditions using the upgraded field-assisted sintering technique (U-FAST). Mixtures of microstructural titanium powders and nc-Ti0.9Mo0.1C/C carbide powders protected from oxidation by a carbon shell were subjected to sintering. The powders with nc-Ti0.9Mo0.1C/C contents of 10 and 20 wt% were used. The content of carbon forming the carbon shell was approximately 3 or 40 wt%. Composites with near full density were reinforced with titanium carbides in a Ti-Mo matrix. The composites with the highest content of reinforcing phase are characterized by the highest values of hardness, Young's modulus and wear resistance. Although the hardness of these composites is similar to that of ceramics, their nature is not brittle. Despite the high value of the Young's modulus, the addition of hard particles of the reinforcing phase to the titanium matrix significantly increases the values of the H/E ratio of the composites compared to the reference samples of cp-Ti and Ti6Al4V. A comparison of the research results for the composites with the highest share of titanium carbides showed that lowering the sintering temperature from 1300 to 1150 ◦C resulted in the inhibition of grain growth, a reduction in composite heterogeneity, composite roughness and hardness as well as a rise in the Young's modulus. An increase in the sintering temperature from 1150 to 1300 ◦C contributed to the higher high angle grain boundaries (HAGB) content.
Journal of Alloys and Compounds, 2016
TiC-Ni based cermets were prepared by vacuum sintering at 1200°C, 1300°C and 1400°C. NiB (0, 10, 20 wt %) was added to improve sintering activity by creating a liquid phase and enhance the densification. The effects of NiB content on density, microstructure, hardness, elastic modulus, fracture toughness, and thermal expansion were studied. Density, micro hardness, elastic modulus, and fracture toughness, of the composite were increased by the addition of 10 wt% NiB. The 1400°C sintered sample with 10wt% NiB resulted in maximum densification with 97% of theoretical density. The 1400°C sintered TiC-10Ni-10NiB showed better mechanical properties with elastic modulus of 470GPa , hardness of 2759 HV and fracture toughness 8.98MPa.m 1/2 , all better than that of TiC-20Ni sintered at same condition.
Spark Plasma Sintering of Nanostructured TiCrC Carbides Prepared via Mechanical Alloying
2022
In order to produce nanostructured Ti0.9Cr0.1C powders, an elemental powder mixture of titanium, chromium, and graphite is milled in this work using a high-energy ball mill for various milling times. Microstructural characteristics such as crystallite size, microstrain, lattice parameter, and dislocation density are determined using X-ray diffraction (XRD). Mechanical alloying successfully produced nanocrystalline (Ti,Cr)C with an average crystallite size of 11 nm. This size of the crystallites is also directly verified using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used to investigate the morphology of the samples. The novelty of this work is advancing the scientific understanding of the effect of milling time on the particle size distribution and crystalline structure, and also understanding the effect of the spark plasma sintering on the different properties of the bulks. Densified cermet samples were produced from the nanocrystalline powders, milled for 5, 10 and 20 hours by SPS process at 1800 degrees for 5 min under a pressure of 80 MPa. Phase changes of the produced cermets were examined according to XRD, SEM/EDX analyses. Significant amounts of Cr and Fe elements were detected, especially in the 20 h milled cermet. The bulk forms of the milled powders for 5 and 20 h had a relative density of 98.43 and 98.51 %, respectively. However, 5 h milled cermet had 93.3 HRA because of the more homogeneous distribution of the (Ti,Cr)C phase, the low iron content and high relative density. According to the 0.0011 mm/year corrosion rate, and 371.68 kΩ*cm 2 charge transfer resistance obtained from the potentiodynamic polarization and EIS tests, the 20 h cermet was the specimen with the highest corrosion resistance.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1996
The effect of Mo additions on the microstructure and mechanical properties of TiC-30 wt.% Ni cermets produced by the combustion synthesis-impact forging technique was investigated. The Mo content was varied between 0 and 10 wt.%, in 2 wt.% increments. Cylindrical tiles 6.35 cm in diameter and 1.27 cm thick were produced with apparent densities above 99%. Microscopically, the addition of Mo resulted in a decrease in the number of microstructural defects such as interphase debonding and binder microcracking. The microstructure consisted of a spheroidal carbide phase with a high degree of contiguity (decreasing with increasing Mo content). The Mo additions did not have a profound effect on the carbide phase morphologies (faceted vs. spheroidal), mean apparent particle diameters (3.5 μm–4.5 μm), or particle size distribution. Energy-dispersive X-ray analysis revealed Mo preferentially in the carbide phase, with trace amounts in the Ni alloy binder. A significant amount of Ti was found in solution with Ni. Vickers' microhardness did not vary significantly with Mo content and was approximately 13 GPa. Compressive strength, transverse rupture strength, fracture toughness, and Young's moduli increased with increasing Mo content; the mean values for the 8 wt.% Mo material were approximately 3400 MPa, 1300 MPa, 22 MPa m1/2, and 340 GPa respectively. The beneficial effect of Mo is due to the improved wettability of the Ni alloy binder on the carbide phase. Improved wettability results in a decrease in detrimental microstructural defects and an increase in the interphase bond strength and phase uniformity.
Effect of coalescence on the grain coarsening during liquid-phase sintering of TaC–TiC–Ni cermets
Acta Materialia, 2000
AbstractÐDuring heat treatment of TaC±2TiC±30Ni (in wt%) specimens at 14008C, abnormally large and faceted (Ta, Ti)C grains appeared. These abnormal grains usually coalesced with surrounding small grains and grain boundaries were formed between them. Inside the abnormally grown large grains, many small grains were entrapped. The observed abnormal grain growth (AGG) was explained in terms of a twodimensional nucleation controlled growth mechanism. Coalescence was suggested to enhance the growth rate because re-entrant edges due to grain boundaries provide easier two-dimensional nucleation sites. 7
International Journal of Refractory Metals and Hard Materials, 2006
Reactive carburizing sintering is a novel process where synthesis reaction of the carbide phase is combined with liquid phase sintering of the Cr 3 C 2-Ni cermet. This recently developed method is compared with traditional cermet industry routine. Powder of chromium, nickel, and carbon black were milled in a high-energy ball mill (attritor) to nanocrystalline size and pressed to compacts. During the next step-thermal treatment-the chromium carbide is formed and the cermet is sintered in one cycle. It is shown that mechanical properties, erosion, and wear resistance depend on the carbide-to-binder ratio, sintering parameters, and manufacturing technique. Reactive sintering allows for the acquisition of a uniform fine-grained cermet with high mechanical and tribological properties and to decrease the production costs of alloys.
Materials
This paper describes the microstructure and properties of titanium-based composites obtained as a result of a reactive spark plasma sintering of a mixture of titanium and nanostructured (Ti,Mo)C-type carbide in a carbon shell. Composites with different ceramic addition mass percentage (10 and 20 wt %) were produced. Effect of content of elemental carbon covering nc-(Ti,Mo)C reinforcing phase particles on the microstructure, mechanical, tribological, and corrosion properties of the titanium-based composites was investigated. The microstructural evolution, mechanical properties, and tribological behavior of the Ti + (Ti,Mo)C/C composites were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction analysis (EBSD), X-ray photoelectron spectroscopy (XPS), 3D confocal laser scanning microscopy, nanoindentation, and ball-on-disk wear test. Moreover, corrosion resistance in a 3.5 wt % NaCl sol...