Addition Of Hard Particles Research Articles

Development of a novel wear-resistant WC-reinforced coating based on the case-hardening steel Bainidur AM for the substitution of carburizing heat treatments

Laser-based directed energy deposition of metals (DED-LB/M) supports the synthesis of functional materials with tailored properties and performance through in-situ modification of the alloying composition within the processing zone. In this investigation, a low-alloyed steel was modified stepwise to analyse the influence of carbon and tungsten carbide (WC) addition on the resulting material properties. A moderate carbon concentration of 0.4 wt.-% improved the average hardness (520 HV0.5). WC particles on the other hand were dissolved within the matrix and resulted in a fine microstructure with high hardness (780 HV0.5). A combined addition of carbon and WC led to the highest material hardness (840 HV0.5). Scratch tests showed that the wear resistance rises with increasing hardness but is improved the most by the addition of hard particles. Furthermore, these tests revealed an anisotropic abrasive wear resistance which correlates with the direction of the weld tracks. Loading the material parallel to the weld track direction led to a homogeneous wear. When the material is scratched perpendicularly to the weld tracks, an inhomogeneous wear with periodic characteristics occurred. The periodicity can be explained by the different microstructural characteristics and hardness at the transition zone between adjacent weld tracks deposited in DED-LB/M. For all materials, the transition between two weld tracks was characterized by a columnar microstructure with low microhardness while the adjacent weld tracks possessed a finer microstructure and higher microhardness. These microstructural differences were mirrored in scratch testing since wear peaks can be observed at the transition zone between two weld tracks.

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.

Meso-scale numerical simulation and experimental verification of single grain grinding TiC–Fe composites

Grinding process of particle reinforced metal matrix composites (PRMMCs) is extremely challenging due to the addition of hard particles. To reveal the material removal mechanism, a meso-scale numerical model for single grain grinding of TiC–Fe composites was established, considering the random particle distribution model and cohesive zone model. The simulated grinding forces and machined surface topography based on the proposed model show a similar trend and were consistent with the experimental results. The transition stage of ductile-brittle removal of TiC–Fe composites was explored. Results indicated that the grinding forces increase abruptly due to the obstruction of high-strength TiC particles and fluctuate periodically in the Fe matrix. The grinding forces decrease with the elevated grinding speed. Additionally, the material removal processes at different stages were studied and the removal modes mainly include: matrix plastic removal, particles wear, particles debonding, particles fracture, particles pull out. This paper provides significant guidance for the digitization and information construction of PRMMCs machining in enterprises and increases the economic benefits for the manufacturing industry.

The influences of high temperature on tribological properties of Cu-based friction materials with a friction phase of SiO2/SiC/Al2O3

Cu-based friction materials have better tribological properties, high mechanical strength, and excellent thermal conductivity; therefore, they are widely used as friction materials in high-speed rail brake systems. However, with the remarkable increase in running speed of high-speed trains, a great amount of energy and high temperature are induced in the brake system; therefore, new challenges are generated for brake pad materials. In this paper, Cu-based friction materials were prepared with the addition of various hard particles as the friction phase, in order to obtain a good high temperature tribological performance. The experimental results showed that the Cu-based friction materials with addition of hard particles have moderate mechanical strengths and proper tribological properties. The temperature effects on the tribological behaviors of friction materials were investigated. The coefficient of friction (COF) for friction materials with addition of hard particles increased with temperature, resulting from the integrated effects of friction film, graphite, and material softening. The variation trends of the wear loss and wear rate with temperatures are similar to those of COFs, which are significantly reduced with the addition of hard particles.

Effect of hard particles on the ferromagnetic transition in dipolar fluids, a simulation study

We investigate by Monte Carlo simulation how the ferromagnetic ordering transition in a polar fluid is affected by the addition of nonpolar particles. To this end, we consider a mixture of dipolar and pure hard spheres of equal size. Using simulations in the Gibbs ensemble, we first determine the demixing domain in the region of high densities and mole fractions of the polar particles. Then, starting from a purely dipolar fluid at two different densities and monitoring the variation of the order parameter, it is shown that the addition of hard particles favours the alignment of the dipoles. The critical temperature of the transition is finally determined and we show how it is modified, depending on the vicinity of the demixing transition. The interplay of the orientational transition and the demixing transition is finally discussed.

The Study on Semi-Blunt Puncture Behavior of Nanofiber Membrane/ Non-Woven Composite Material.

Nanofiber membrane/non-woven composite material is composed of electrospinning nanofiber membrane and non-woven fabric, which combines the supporting role of nonwoven material and the special nano-size effect of nanomaterials. These composite material can be widely used in biomedical, filtration and other related fields. In the actual use process, nanofiber membrane/non-woven composite material is often subjected to external forces such as puncture or bursting. As a result, the mechanical study of nanofiber membrane/ non-woven composite materials has a high value and practical significance. The nanofiber membrane/non-woven composite material was obtained by spraying solution (different concentrations of titanium dioxide-loaded Poly (vinyl alcohol) (PVA)) on meltblown polyester non-woven fabric. The surface morphology and fiber diameter of different concentrations nanotitanium dioxide-loaded Poly (vinyl alcohol) fiber were investigated by Field Emission Scanning Electron Microscopy (FESEM). The surface distribution of TiO2 on the electrospun fibrous membranes was characterized by Energy Disperse Spectroscopy (EDS). The semi-blunt puncture behavior of different concentrations of nano-titanium dioxide-loaded nanofiber membrane/non-woven composite material was conducted by universal material machine. With the increase of concentrations of nano-titanium dioxide particles, the surface smoothness of nanofibers diminishes, the unevenness of the diameter distribution of the fiber increased and the maximum semi-blunt puncture strength increased. The addition of hard particles does contribute to improving the puncture properties of the composite materials. Several patents, related to electrospinning and bubble electrospinning equipment for nanofiber fabrication, have been reported.

Influence of addition of hard particles on the mechanical and chemical behavior of vitreous enamel

The vitreous enamel coatings present very interesting properties for several industrial applications due to the glassy nature of the matter. Their chemical resistance and corrosion protection properties result very high due to the glassy nature of deposits. A good wear behavior is also requested in some applications. The use of composite layer obtained by the addition of hard particles to enamel could be a possible solution to increase the deposits hardness. In literature, there are some work about the chemical nature of the added particles, but the influence of the dimension and quantity of these particles are not well studied. The aim of this work is the study of composite enamel layers deposited on low carbon steel substrate with addition of Al2O3 particles characterized by macro and micro dimensions with different concentration (5, 10 and 20 wt.%). After the microstructure characterization, the abrasion resistance behavior is evaluated by Taber Test following ASTM C501 for 1500 cycles. Mass loss, gloss and roughness changes are collected. The protection properties change is evaluated by Electrochemical Impedance Spectroscopy measurements. The addition of micro dimension particles produces the best behavior. On the contrary, the presence of macro dimension particles reduces the abrasion resistance, probably caused by the increase of porosity level during firing treatment. Finally, the corrosion protection properties are evaluated by Kesternich test (aggressive fog with the presence of SO2), simulating an industrial environment. In this case the presence of the micro- particles shows a limited resistance. Probably the presence of the particles produces an increase of surface roughness and a presence of higher quantity of particles in surface, which favor the start of enamel degradation with a loss of protection properties. Increasing the quantity of particles, a reduction of chemical resistance is observed.

Effect of tungsten carbide addition on the tribological behavior of Astaloy 85Mo powder consolidated via spark plasma sintering

Abstract Hard particle addition in ferrous powders allows the production of sintered materials with higher toughness, hardness and wear resistance, with potential use in different technological applications. This combination of properties is attained following correct mixture and sintering procedures that result in the formation of composites with low porosity and adequate particle distribution. In this work, Astaloy 85Mo ferrous powders were mixed with different tungsten carbide (WC) additions (2, 5, 7 and 10 wt%) by mechanical alloying (MA) and consolidated by spark plasma sintering (SPS), providing samples with higher real density, and without an increase in porosity (or apparent volume). SPS enhanced sinterability using low sintering time that reduces carbon diffusion from WC to the ferrous matrix. Tribological evaluation was conducted by means of ball-on-disk tests with different loads (5, 10, 15 and 20 N). Specimens were in contact with an AISI 52100 ball with a diameter equal to 10 mm and the friction and wear coefficient of both bodies in contact were reported. Results indicated that WC addition contributed to load support and decrease of matrix plastic deformation. Additions higher than 7 wt% of WC, in conditions of high normal load, resulted in the detachment of WC particles and abrasive wear of the counterpart.

Adaptation of TiC Hard Particles Properties and Morphology in Metal Matrix Composites by Refractory Elements

High mechanical loads, corrosion, and abrasion decrease the lifetime of tools. One way to increase the wear resistance of tool materials can be achieved by adding hard particles to the metal matrix such as titanium carbide, which protect the softer metal matrix against abrasive particles. This material concept is designated as metal matrix composite (MMC). Ferro-Titanit® is such MMC material, possessing high wear and a simultaneously high corrosion resistance, for which reason this material is used in the polymers industry. The material concept is based on a corrosion-resistant Fe-base matrix with up to 45 vol% titanium carbide (TiC) as a hard particle addition to improve the wear resistance against abrasion. These TiC hard particles must be adapted to the present tribological system in terms of hardness, size and morphology. This study shows how the size and morphology of TiC hard particles can be influenced by the refractory element niobium (Nb). Therefore, the element Nb was added with 2 and 4 mass% to the soft-martensitic Ferro-Titanit® Grade Nikro128. The investigated materials were compacted by sintering, and the densified microstructure was further characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDX), and optical image analyses. Furthermore, microstructure and properties of the compacted Nb-alloyed samples were compared to the reference material Nikro128. The results show that the addition of Nb influences the morphology, size and chemical composition of the TiC hard particle. These changes in the hard phase characteristics also influence the materials properties. It was shown that the phase niobium carbide (NbC) is formed around the TiC during the densification process, leading to a change in morphology and size of the TiC.

The Effect of Dispersion Phases of SiC and Al2O3 on the Properties of Galvanic Nickel Coatings

In this study, Ni, Ni-SiC and Ni-Al2O3 coatings were electroplated on the 2xxx series aluminium alloy. The following parameters of the electroplating process were applied: current density - 4A/dm2, time - 60 minutes, and temperature - 60°C. Hard particles of submicrometric size were used. The results of the research showing the effect of the addition of hard particles (introduced into the nickel bath as a dispersed phase) on the properties of coatings, including the effect of the type (SiC or Al2O3) and content (0, 25, 50 g / l) of these particles, were discussed. Based on extensive investigations, it was found that the type of ceramic particles significantly affects the structure of produced coatings. The dispersed particles incorporated into the nickel coatings improve their abrasion resistance. Improving of the corrosion properties were observed only in the case of coatings containing silicon carbide particles.

Abrasion and chemical resistance of composite vitreous enamel coatings with hard particles

Vitreous enamels are coatings commonly used to protect aluminium substrates, because of their very good protection properties together with aesthetical ones. The properties of this layer can be optimized changing the chemical composition of the starting frit or with mill additives. The addition of hard particles, very common method with other types of coatings, for this layer has not yet been studied. The aim of this research is to study how the addition of hard particles influences the mechanical and chemical resistance of enamels applied on AA4006 alloy. Deposits with two different kinds of particles [tungsten carbide (WC) and silicon carbide (SiC)] with two concentrations were considered. The enamel layer without particles was considered as reference. Two different kinds of abrasion test (Taber and PEI) were adopted to study the abrasion resistance. Enamel coatings' properties were characterized considering the changes in mass, gloss and roughness values before and during abrasion tests. Moreover, the observation of cross sections and surfaces permitted to evaluate the coatings' quality and to obtain information about the damage mechanisms. The most improved abrasion resistance was achieved using the concentration of 10 vol% for SiC and 5 vol% for WC. Therefore, the adding of hard particles could be a valid solution to improve the abrasion resistance of the vitreous enamels. The chemical resistance behaviour was checked with immersion into acid and basic solutions. The presence in the layer of SiC particles produced a reduction of resistance in presence of acidic solution, while enamel with WC particles resulted more resistant. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of both nano-size alumina particles and severe deformation on polyethylene crystallinity index

The morphological and microstructural changes during ball milling of PE powder mixed with different weight percent (5–15 wt%) of Alumina particles (50–100 nm) were studied. The milling was performed in a planetary ball mill for various times up to 40 h. The results showed that the addition of hard particles accelerates the milling process, leading to fracture of polyethylene matrix. The result of X-ray diffraction analysis determined that the degree of crystallinity of polyethylene decreased by increasing of ball milling time and weight percent of Alumina.

Effect of water conditioning on the fracture behavior of PA12 composites processed by selective laser sintering

This study aims to elucidate the combined effects of reinforcing particles and water on PA12 processed by selective laser sintering (SLS). PA12 is one of the toughest polyamides. However, PA12 processed by SLS is rather brittle due to the presence of voids and the relative low molecular weight of the polymers used in SLS. It is demonstrated that humidity impoverishes the mechanical properties of neat PA12, including ductility and toughness. A ductile/brittle transition was detected, which was attributed to the competition between the plasticizing effect and the hydrolization of PA12 molecules plus the increase in crystallinity which counteracted this mechanism. It has been found that addition of hard particles, such as glass spheres and ceramic fibers, prevents the ductile/brittle transition by water conditioning at high temperature to happen.

Influence of nanosized Al2O3 weight percentage on microstructure and mechanical properties of Al–matrix nanocomposite

Aluminium based metal matrix composites produced by powder metallurgy are used in the aerospace and automobile industries because of their high strength, light weight, etc. The properties may become much better when nanosized reinforcements are used. In this research, the morphological, microstructural and mechanical properties changes during nanosized alumina increment to Al powder were studied. Because nanosized particles are extremely prone to agglomeration, all of the samples have been milled for 12 h by a planetary ball mill. The process was conducted for Al–(0–20) wt‐%Al2O3 powders to explore the role of reinforcement nanoparticles on the microstructure and mechanical properties. The results showed that the strength, ductility and hardness were increased by increasing the reinforcement nanoparticles weight percentage. Also, addition of hard particles accelerated the milling process, leading to faster work hardening rate and fracture of the aluminium powder.

Effect of Powder Type and Composition on Structure and Mechanical Properties of Cu + Al2O3 Coatings Prepared by using Low-Pressure Cold Spray Process

Powder type and composition have a very important role in the production of metallic and metallic-ceramic coatings by using the low-pressure cold spray process. Furthermore, structure and mechanical properties of Cu and Cu + Al2O3 coatings are strongly influenced by powder characteristics of Cu particles. The aim of this study was to evaluate the effect of different particle types of Cu powder and different compositions of added Al2O3 particles on the microstructure, fracture behavior, denseness, and mechanical properties, i.e., hardness and bond strength. Spherical and dendritic Cu particles were tested together with 0, 10, 30, and 50 vol.% Al2O3 additions. Coating denseness and particle deformation level increased with the hard particle addition. Furthermore, hardness and bond strength increased with increasing Al2O3 fractions. In the comparison between different powder types, spherical Cu particles led to the denser and less oxide-contenting coating structure due to the highly deformed particles.

Mechanical properties of a lithium glass–ceramic matrix (LZSA) reinforced with TiC or (W,Ti)C particles: A preliminary study

Abstract Despite their generally low strength and hardness values, glass–ceramics show good potential to be used in structural applications at room temperature instead of other costlier ceramic materials. This work investigates the effect of dispersed hard carbide particles on the sintering behaviour and the mechanical properties of a lithium glass–ceramic. The glass was mixed with 30 wt.% TiC or (W,Ti)C and hot-pressed at 650 °C (30 MPa, 30 min, Ar). The results obtained compare the properties of the composites with those of the parent glass and demonstrate that the addition of hard particles significantly improves the mechanical strength of the glass–ceramic matrix.

Room temperature hardness of carbide strengthened cast alloys in relation with their carbon content and aging temperature Part 1 – Case of nickel alloys

The addition of hard particles in a ductile alloy may lead to a substantial increase in its hardness and in the difficulty to machine it. The present work aims to specify the role of chromium carbides in the hardness of cast nickel alloys. A Ni–30 wt-%Cr alloy and six 0·2–2 wt-%C containing alloys based on the first one were elaborated by foundry. Their microstructures after aging at 1000, 1100 and 1200°C were described, and the room temperature, Vickers hardness of all the alloys for the three aging treatments were measured. Hardness increases with carbon content following a curve which is almost parabolic, while it increases more linearly versus the volume fraction of carbides. Hardness is generally lowered by choosing higher aging temperature. The evolution of hardness was compared with a law of mixture based on the hardness and the volume fractions of the matrix and of the carbides.

Influence of hard particle addition and chemical interdiffusion on the properties of hot extruded tool steel compounds

Low alloyed steel bars were co-extruded with pre-sintered tool steel powders with the addition of tungsten carbides (W 2C/WC) as hard particles. During the hot extrusion process of these massive and powdery materials, an extrudate is formed consisting of a completely densified wear resistant coating layer and a bulk steel bar as the tough substrate core. This work combines experimental measurements (EPMA) and diffusion calculations (DICTRA™) to investigate the effect of hard particle addition and its dissolution, as well as the formation of M 6C carbides on the properties of two different PM tool steel coatings hot extruded with a 1.2714 steel bar. A carburization effect resulting from the W 2C hard particles is responsible for an increase of the 1.2344 steel matrix hardness. The mechanical properties of the interface region between coating matrix and substrate are influenced by chemical interdiffusion of carbon and other alloying elements occurring during heat treatment.

Influence of gas atmosphere and hard particle addition on the sintering behavior of high alloyed PM cold work tool steels

Sintering of two different gas atomized PM cold work tool steels, X220CrVMo13-4 (X220) and X245VCrMo9-4 (X245), in argon, nitrogen and forming gas (N 2–5% H 2) was investigated with respect to the atmospheric influence. To ascertain the influence of hard particle additions, coarse powders of TiC and WC/W 2C were mixed with the steel powder at a volume fraction of 5 vol.%. The objective of these investigations was to detect optimal sintering parameters for the processing of sintered wear resistant metal matrix composites. Additionally, the disastrous influence of fused tungsten carbide particles added to tool steel powders during sintering ought to be clarified. Experiments were carried out using dilatometry, high temperature X-ray diffraction, protective gas sintering and scanning electron microscopy. To support the experiments theoretically, pressure dependent Thermo-Calc calculations were performed.

Wear Resistance Properties of Tungsten Carbide/Stainless Steel Composite Materials Prepared by Pulsed Current Sintering

Austenitic stainless steel has been used as a corrosion resistance material in tough corrosive circumstance. However, austenitic stainless steel has poor wear resistance property due to its low hardness. Tungsten Carbide alloys (WC) are widely used as tooling materials, because of their high hardness and excellent wear resistance property. In this investigation, we apply powder composite process to obtain hard layer of Stainless steel. The composite material was fabricated from planetary ball milled WC powder and SUS316L stainless steel powder and sintered by Pulsed Current Sintering (PCS) method. We also added TiC powder as a hard particle in WC layer. Evaluations of wear properties were performed by pin-on-disk wear testing machine, and a remarkable improvement in wear resistance property was obtained. The weight loss rate of the composite was 1/10 of SUS316L. In addition, it was found that TiC hard particle addition has a positive effect on the wear resistance property. EPMA investigation showed good dispersion of WC hard phase and TiC hard particle with SUS316L matrix.