Metallic Binder Research Articles

Thermal Frequency Drift of 3D Printed Microwave Components

Fabrication of microwave slot array antennas and waveguide bandpass and notch filters using 3D printing has significant advantages in terms of speed and cost even for parts with high mechanical complexity. One disadvantage of Stereolithography (SLA) 3D printed, copper plated microwave components is that some SLA resins have a high Coefficient of Thermal Expansion (CTE), quoted in micrometers per meter per degree or 10−6 per degree. Compared to typically used metals such as aluminum (CTE 24 × 10−6·K−1) and copper (CTE 17 × 10−6·K−1), SLA resin can have CTE above 100 × 10−6·K−1. Resonant structures experience significant frequency drift with temperature changes on the order of 10–50 °C. The issue of 3D printed microwave structures changing frequency characteristics significantly with temperature shift has not been addressed or reviewed in current literature. We measured and simulated the effect of temperature change on a slot array, cavity notch filters, and post loaded waveguide bandpass filters. We tested several types of SLA resin, different plating techniques, and also Direct Metal Laser Sintering (DMLS) and Binder Infusion metal 3D printing. Performance as a function of temperature is presented for these alternatives.

Indentation and scratch testing of a WC-6%wtCo cemented carbide: Corrosion effects on load-bearing capability and induced damage

In this work, corrosion effects on the indentation and scratch response of a WC-6%Co hardmetal are investigated. Experimental variables include relative long corrosion times as well as indentation and scratch testing conditions yielding damage scenarios whose depths are similar to length scale of the degraded surface layers. It is found that load-bearing capability and crack extension resistance of the cemented carbide grade studied are significantly reduced after exposure to corrosive media. This is related to relevant changes within the microstructural assemblage of the material, from an effective bulk ceramic-metal composite into a porous layer consisting of a binderless carbide network on top of a pristine-like hardmetal substrate. However, such lessening effects are found to be dependent on the ratio between indentation and/or scratch depth and thickness of the corroded layer. Hence, relative changes decrease as corrosion time increases, and no differences are discerned after seven days of immersion. Similar pronounced corrosion influence is evidenced in surface and subsurface damage scenario resulting after indentation and scratch tests. In this regard, a transition from well-defined cracking systems into a scenario consisting of multiple, branched and less shallow fissures is evidenced when comparing pristine and corroded specimens respectively. The experimental fact that referred cracking features for corroded specimens are confined within the porous-like degraded layers points out that it is the result of small length-scale interaction between cracks and the cavities within the binderless WC skeleton, left after the metallic binder has been leached away.

Electrolytic properties and element migration in Ni–TiB2/Al2O3 composite cathode

With alumina sol as binder and Ni metal as sintering aids, the Ni–TiB2/Al2O3 composite cathode material for aluminum electrolysis was prepared by cold-pressed sintering. The mechanical properties of the composite cathode material were measured. Its electrolytic properties were identified by a 20-A electrolysis test. Cathode samples before and after electrolysis test were measured by energy-dispersive spectroscopy (EDS). The migration behavior of various elements in the electrolysis process was studied by phase analysis. The result shows that Ni metal can effectively fill the gap between the aggregate during the sintering process, which can improve the sintering density of the composite cathode material significantly. The voltage of the 20-A electrolysis test is stable. The impurity of aluminum liquid is 0.42%. The aluminum liquid can wet the cathode surface effectively, and the Ni–TiB2/Al2O3 composite is an ideal wettable cathode material. In the process of electrolysis, the alkali elements in the electrolyte penetrate the electrode, where K goes deeper than Na. Al generated on the cathode surface will also penetrate the cathode through the gap of the composite material, while Ni in the electrode will spread into the aluminum liquid layer.

Mineralogy and Zn Chemical Speciation in a Soil-Plant System from a Metal-Extreme Environment: A Study on Helichrysum microphyllum subsp. tyrrhenicum (Campo Pisano Mine, SW Sardinia, Italy)

Environmental contamination due to human activities is a worldwide problem that has led to the development of different remediation techniques, including biotechnological approaches such as phytoextraction and phytostabilization. These techniques take advantage of pioneer plants that naturally develop tolerance mechanisms to survive in extreme environments. A multi-technique and multi-disciplinary approach was applied for the investigation of Helichrysum microphyllum subsp. tyrrhenicum samples, bulk soil, and rhizospheres collected from a metal-extreme environment (Zn-Pb mine of Campo Pisano, SW Sardinia, Italy). Zinc, Pb, and Cd are the most abundant metals, with Zn attaining 3 w/w% in the rhizosphere solid materials, inducing oxidative stress in the roots as revealed by infrared microspectroscopy (IR). X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis coupled with synchrotron radiation-based (SR) techniques demonstrate that quartz, dolomite, and weddellite biominerals precipitate in roots, stems, and leaves, likely as a response to environmental stress. In the rhizosphere, Zn chemical speciation is mainly related to the Zn ore minerals (smithsonite and hydrozincite) whereas, in plant tissues, Zn is primarily bound to organic compounds such as malate, cysteine, and histidine molecules that act as metal binders and, eventually, detoxification agents for the Zn excess. These findings suggest that H. microphyllum subsp. tyrrhenicum has developed its own adaptation strategy to survive in polluted substrates, making it a potential candidate for phytostabilization aimed at mitigating the dispersion of metals in the surrounding areas.

An investigation on the development and wear performance of chromium-MWCNTs transformed HVOF sprayed nano-WC-CoCr coatings

This research work presents a detailed study of development and wear performance of high chromium and multiwalled carbon nanotubes (MWCNTs) reinforced nano-WC-CoCr based coatings. The CoCr binder matrix was modified by increasing the Cr element (10 & 16 wt%) and keeping the fixed proportion of MWCNTs (2 wt%). The coating deposition was done by using Praxair JP-5000 HVOF spray gun with optimized process parameters. SEM, EDS, and XRD were performed to study the surface morphologies, elemental compositions and phases present in the feedstock powders and developed coatings. Micro-hardness, percentage porosity, surface roughness and indentation fracture toughness of the deposited coatings were evaluated. The solid particle erosion and reciprocating abrasive wear testing were conducted in order to evaluate the wear resistance of modified coatings. The worn-out surfaces obtained after erosion testing revealed the removal of material by microcutting and ploughing of CoCr binder matrix, pull-out and fracturing of nano-WC grains. The SEM images revealed the formation of wear tracks on the coatings surfaces, which were caused by the micro-cutting and sideways displacement of CoCr and nano-WC grains during the reciprocating abrasive wear testing. The addition of Cr in higher proportion along with MWCNTs significantly enhanced the fracture toughness of nano-WC-CoCr coating. The improvement in fracture toughness may be attributed to increased metallic binder contents along with the bridging and gluing of splats by MWCNTs. The nano-WC-CoCr coating with 10 wt% Cr + 2 wt% MWCNTs exhibited the enhanced wear resistance in all the test conditions as compared to the other coatings.

Densification Kinetics of Titanium Carbide- Based Cermet During the Pressure Sintering

Titanium carbide-based cermets with the addition of other carbides and with metal binders of nickel, iron and their alloys are used in mechanical engineering technology and instrumentmaking industry as wear-resistant and corrosion-resistant materials and coatings. The goal remains to increase the mechanical and functional properties of cermets, and for this research is being conducted aimed at optimizing the compositions and improving the technology for their manufacture.

Indentation behavior of highly confined elasto-plastic materials

The effect of geometric confinement is well-known from hardness measurements of thin films on stiff substrates and has been modeled both phenomenologically and using e.g. Finite Element Analysis. However, these models are mainly focused on a specific experiment or a certain material family. In the present work, Finite Element Analysis is used to gain a better understanding of the interplay between geometric constraints in various microstructures and a wide range of materials properties. It is shown that a very simple model can be used to replicate thin film hardness data where the film is softer than the substrate as well as how materials properties alter the indentation behavior of materials confined in one to three dimensions. It is shown that qualitative agreement with nanoindentation of the metallic binder phase in the complex 3D-microstructure of a cemented carbide is achieved using an axisymmetric “pill-box” model with classical plasticity. It is also shown that the effect of higher-order confinement can be described by the Korsunsky thin film hardness model by re-optimizing the fitting parameters.

In-situ metal binder-phase formation to make WC-FeNi Cermets with spark plasma sintering from WC, Fe, Ni, and carbon powders

High-density WC-FeNi ceramic-metal (cermet) composites were fabricated using liquid-phase spark plasma sintering/field-assisted sintering technology (SPS/FAST) with in-situ formation of metal binder phase. The precursor materials were micron-sized powders of WC, Fe, Ni, and C. A low melting point from a eutectic reaction of the powders enabled the in-situ formation of FeNi alloy and facilitates liquid-phase sintering of the WC. The carbon powder was added to stabilize the formation of the binder phase. Electron backscatter diffraction (EBSD) was performed to measure grain size and orientation. The composite exhibited a 99% theoretical density and a microstructure consisting of rounded and contiguous WC grains. The average grain size is 10.5 μm. The composite has a maximum hardness of 16.1 GPa. This research provides a fast and cost-effective approach to fabricate hard metals.

Preparation, mechanical and tribological properties of WC-Al2O3 composite doped with graphene platelets

Advanced mechanical and tribological properties are the premises for the novel WC-Al2O3 ceramic composite without metallic binder phase to be industrially applied. For this purpose, 0.3 wt% graphene platelets were doped during the fabrication of WC-Al2O3 ceramic composite in this work. Characterization showed graphene platelets were homogeneously distributed in the ceramic matrix. Graphene platelets additions refined the grain size, increased the hardness (from 16.18 to 18.34 GPa) and fracture toughness (from 8.08 to 11.02 MPa m1/2). Graphene platelets additions reduced the friction coefficient (from 0.47 to 0.28, under 40 N; from 0.57 to 0.38, under 60 N) and the specific wear rate (from 1.21 × 10−5 to 1.32 × 10−6mm3N−1m−1, under 40 N; from 2.18 × 10−5 to 6.72 × 10−6mm3N−1m−1, under 60 N), based on the ball-on-disk dry sliding.

Performance evaluation of coated cermet insert in hard turning

Cermet comprises of a ceramic matrix, which is bonded through a metallic binder. The addition of metal coating layers enhance the toughness as well as the thermal resistance of the ceramic. Cermet is mainly recommended for chemical-resilient, high-temperature applications and as insulators. However, current work emphasized on performance evaluation of multi-layered coated (TiN/TiCN/TiN) cermet (golden colour) inserts in the dry-hard turning of AISI 4340 steel. The performance of the coated cermet insert was rarely investigated in hard turning. However, it is quite interesting to know its machining capability of the harder workpiece in terms of surface roughness (Ra), the material removal rate (MRR) and chip reduction coefficient (CC). In entire set of L9 experiments, Ra was found to be in the range of 0.212 to 1.452 µm, i.e. within 1.6 µm (standard criteria), hence it justifies that the coated cermet tool can be implemented in hard turning applications to get good quality of finish. Input-terms influence on machining attributes is studied with the help of main effect plot, contour plot, surface plot, and ANOVA. Depth of cut is the supreme input terms to influence the MRR and CC by a contribution of 90.53% and 83.14% exclusively, while feed and depth of cut both are influencing Ra significantly with the contribution of 55.03% and 44.09% correspondingly. Correlation models are formulated using regression theory and found to be satisfactory at 0.05 of the level of significance.

Novel approaches in manufacturing of multicomponent metallic binders for diamond cutting tools

In this study, three approaches for the diamond cutting tool binder improvement are shown. They allow to reinforce the binders and enhance their wear resistance, thus making diamond grain retention in the working layer of the tool more reliable. Mechanical alloying methos was used to obtain a homogeneous and nanocrystalline structure of the powder binders. It increases the bending strength of iron- and copper-based binders by 60-100 %, to 2500 and 1200 MPa, respectively. The positive effects achieved by adding different types of nanoparticles are summed up during hybrid modification of the binders. It has been verified, both theoretically and experimentally, that hybrid modification with WC and hBN nanoparticles, as well as carbon nanotubes, simultaneously increases binder strength by 20% and improves binder wear resistance during machining of abrasive materials threefold. Doping iron-based binders with adhesively active elements (titanium, chromium, etc.) enhances the diamond retention capacity due to formation of carbide interlayers at the metal–binder interface.

Electrical discharge truing of a PCD blade tool on a dicing machine

It is expected that SiC will be adopted as a semiconductor substrate for next-generation devices. However, SiC is hard and brittle making dicing difficult. Sintered polycrystalline diamond (PCD) has a high degree of hardness and wear resistance, thus, dicing of SiC with thin PCD blade tools has been attempted. However, dicing machine blade run-out causes chipping and/or cracking of the machined surface, necessitating truing of the run out on the dicing machine. As PCD contains a binder metal such making it conductive, EDM is possible. Further, the electrical resistivity of pure water is high, thus, it can be used as both a dicing fluid and an EDM processing fluid. Therefore, it is expected that electrical discharge truing (ED-truing) for thin PCD blades for dicing is possible. Herein, the dicing performance of a thin PCD blade trued by EDM in pure water is discussed. It is demonstrated that it is possible to true the runout of a PCD blade as proposed, and that there is no difference in flexural strength between PCD EDMed in deionized water and oil. Further, chip- and crack-free machining of SiC was demonstrated with an ED-trued ultra-thin PCD blade.

Distinguishing contributions of ceramic matrix and binder metal to the plasticity of nanocrystalline cermets.

Using the typical WC-Co cemented carbide as an example, the interactions of dislocations within the ceramic matrix and the binder metal, as well as the possible cooperation and competition between the matrix and binder during deformation of the nanocrystalline cermets, were studied by molecular dynamics simulations. It was found that at the same level of strain, the dislocations in Co have more complex configurations in the cermet with higher Co content. With loading, the ratio between mobile and sessile dislocations in Co becomes stable earlier in the high-Co cermet. The strain threshold for the nucleation of dislocations in WC increases with Co content. At the later stage of deformation, the growth rate of WC dislocation density increases more rapidly in the cermet with lower Co content, which exhibits an opposite tendency compared with Co dislocation density. The relative contribution of Co and WC to the plasticity of the cermet varies in the deformation process. With a low Co content, the density of WC dislocations becomes higher than that of Co dislocations at larger strains, indicating that WC may contribute more than Co to the plasticity of the nanocrystalline cermet at the final deformation stage. The findings in the present work will be applicable to a large variety of ceramic-metal composite materials.

Manufacture of Tungsten Heavy Alloy Tube by Diffusion Bonding of Semicircular Tubes

An innovative manufacturing method to fabricate tubular parts made of tungsten heavy alloy (THA) by diffusion bonding of sintered semicircular tubes is proposed and characterized in this study. THAs are produced by blending tungsten grains with a lower-melting-point Ni-Fe binder metal. During the liquid phase sintering (LPS) process of THA, the Ni-Fe liquid wets the tungsten and provides a soluble diffusion network for rapid sintering. Multi-phase THAs are usually very difficult to produce as a tubular piece. During the LPS of the powder compact, a gravity-induced slumping leads to some distortion in the bottom of the tubular parts. One possible alternative to handle this problem is to combine the segmented THA pieces by solid-state diffusion bonding to build up tubular piece. Thus, this study proposes combining the semicircular THA tubes using the diffusion bonding technique to manufacture the tubular THA parts. To provide uniform contact pressures along the joining surfaces, horizontal diffusion bonding is performed using a specially constructed supporting apparatus to reduce the gravity effect. An industry-applicable tube manufacturing process has been well characterized, and its feasibility has been demonstrated by bond quality that was assessed by optical metallography and mechanical testing.

Additive manufacturing: A review on 3 D printing of metals and study of residual stress, buckling load capacity of strut members

Additive manufacturing is emerging technology in the growing industry for the production of parts and it can be used for repairing of parts also. Additive manufacturing is the best suitable name for 3 D printing as it prints the part layer by layer so additive. In additive manufacturing 3 D printing of plastics and metals can be done enormously with precise surface finish and feature quality as required. Focusing more on metal 3 D printing it is done with direct metal sintering, direct energy deposition and Metal binder jetting. The metal sintering process use powder bed with powder metal and laser selectively melts a flattened bed of powder which is done with roller with successive rolling of new layer on previous into desired shape before a new layer is pushed on top of the previous layer and successive scanning and lowering of powder bed until the CAD model is done. So melt back happening melting previous layer again due to solidifying the new layer on the earlier layer. This causes residual stresses because of the unique thermal cycle. This residual stress can lead to the failure of the printed part. This can be overcome by preheating of powder bed which will reduce such kind of problem. The printed part can be scanned for with Scanner dimensional accuracy. Much of the metal contracts after melting so this scanning will help for adjusting the size and dimensioning of the CAD model. The surface texture is also analyzed with the help of microscopes for doing comparison with conventional subtractive methods.

Determination of wear parameters and mechanisms of diamond/copper tools in marble stones cutting

In this paper, a type of soft metal binder of diamond tools (diamond segments) that was consisted of 78% Brass (Cu-10Zn) +16% Bronze (Cu–10Sn) + %6Co was investigated. The first, it was approved that the binder is a soft metal binder by a hardness test for diamond tools in natural stones cutting. Then, the effective factors on grinding efficiency such as specific energy (SE), Cutting force (FC), metal binder removal rate (MRR), grinding ratio (G-ratio), wear resistance and Mean free path (MFP) were evaluated by different formula and equations. On the other hand, the effect of different wear mechanisms on the metal binder and diamond grits of the tool was evaluated by the cutting of a type of very hard marble stone that calls Cappochino Beige Marble (CBM). The existence of wears of abrasive, surface fatigue, impact and erosive were confirmed by scanning electron microscopic observations. According to hardness 73 HRB (hardness of the binder) and the wears, there is a short tools life for the diamond tool due to low wear resistance of the metal binder but, the cutting rate was high. Novelty statementThe rising price of decorative stones will increase the final price of the stones and will overshadow the global market of decorative stones. The presence of cobalt, iron, chromium and nickel powders increases the price of diamond tools because of their high price. On the other hand, due to the higher temperature and time of hot press to produce these tools by the mentioned powders, it will also increase the price. Therefore, in this paper, brass and bronze alloy powders, which are much cheaper than cobalt, iron, chromium and nickel powders, have been used as main metal binder powders to reduce raw material prices and manufacturing process costs. On the other side, due to the creation of a softer metal binder compared with the more expensive and harder binder of cobalt, iron, chromium and nickel powders, it can be affected to increase the cutting speed because of increasing wear of the binder. Therefore, mathematical calculations are essential for the efficiency of the tools' cutting.

Die-less manufacturing of tube by diffusion bonding of unit rods made of tungsten heavy alloy

A die-less method to manufacture tubes by diffusion bonding of rods made of tungsten heavy alloys was developed and characterized. Tungsten heavy alloys are pseudo-alloys of tungsten (W) with small amounts of lower-melting-point binder metals, typically Ni and Fe, and they are widely used in tubular shapes. Due to the excessively high consolidation temperature for W, the fabrication of components is normally done by sintering of powder compacts. During the sintering of W–Ni–Fe alloys, the partially melted Ni–Fe binder metal wets the tungsten powder particles and provides a soluble diffusion network for rapid sintering. However, as the binder metals partially liquefy, this process results in gravity-induced slumping, leading to distortion near the bottom section of the tubular part. This gravity-induced slumping creates significant difficulties during the production of tubular structures. A rod shape is the most stable shape to avoid slumping during sintering. Thus, a method to manufacture tubular tungsten heavy-alloy parts via joining of sintered rods by diffusion bonding was developed. Using an analytical model, the dimensions of the unit rods for fabrication of the target tube shape have been designed. An industry-applicable tube manufacturing process was well characterized, and the feasibility of the process was confirmed.

The Effect of Deposition Rate on Microstructural Evolution in WC-Co-Cr Coatings Deposited by High-Velocity Oxy-Fuel Thermal Spray Process

Tungsten carbide-reinforced cermet composites are widely used as wear- and erosion-resistant coatings due to their combination of hardness, strength, toughness and thermal properties. In this study, WC-Co-Cr coatings were deposited using high-velocity oxy-fuel thermal spray technology under different kinematic spray parameters. The microstructure of coatings was investigated using scanning electron microscopy and transmission electron microscopy techniques, and elemental/phase analysis was completed using x-ray diffraction, electron energy loss spectroscopy and x-ray energy-dispersive spectroscopy. The findings indicated the presence of W2C and W6Co6C in addition to WC and chromium oxide (Cr2O3) in a nanocrystalline cobalt-rich matrix. The newly developed phases (W2C and W6Co6C) were formed as a result of decarburization/oxidation of tungsten carbide (WC). They were found as individual particles (0.2-0.4 µm) embedded in the metallic binder phase as well as surrounding existing WC particles. Nonetheless, increasing the coating deposition rate, i.e., reduction of coating build-up per pass, increased the coating hardness from 1516 ± 124 to 1713 ± 106 HV0.3 and led to a higher degree of phase transformation reactions in the coating.

Strain glass transition of cobalt phase in a cemented carbide

Cemented carbides are hard materials used for the fabrication of cutting tools. They consist of hard micron or sub-micron carbide grains held together in a matrix of a tough metallic binder such as cobalt. The understanding and control of cobalt characteristics are of crucial importance to improve the mechanical properties of WC-Co cemented carbide materials. Indeed, cobalt controls the toughness of the material and its properties seem to condition the durability of cemented carbides. At low temperature, pure cobalt is normally found in hcp structure, while above 426 °C (700 K) it changes to fcc crystalline structure. Remarkably, in cemented carbides, cobalt appears even at low temperature as fcc, otherwise as a mixture of fcc and hcp. It is unsure if these crystal structures are due to the presence of internal stresses or due to W and C soluted atoms. However, this paper demonstrates that cobalt in WC-10wt.%Co cemented carbide may show some characteristics of a glass transition at around 669 °C (942 K) in the 1 Hz frequency range, inducing a glassy state to cobalt, which is of great interest from a fundamental point of view, however challenging to control in materials technology.

Ti(C,N)-based cermets with fine grains and uniformly dispersed binders: Effect of the Ni–Co based binders

Metallic binder is a key factor affecting the microstructure and mechanical properties of Ti(C,N)-based cermets. To optimize the overall performances, cermets with various weight ratios of Ni/(Co + Ni) ranging from 0 to 1 were fabricated by gas pressure sintering. Microstructure, phase formation, interface structure and related mechanical properties of the sintered cermets were investigated. With the increase of the Ni/(Co + Ni) ratios, the black cores became smaller and grains of Ti(C,N) dispersed uniformly. Compared to the pure Ni or Co, Ni–Co binders accelerated the formation of rim phases, and avoided the nonuniform dispersed binder pools. When the ratio was 0.5, the cermets showed fine grains, uniformly dispersed binders and small lattice misfit of the core-rim interface, exhibiting the optimal mechanical properties, i.e. satisfactory Vickers hardness of 1670 (HV30) Kgf/mm2, bending strength of 1970 MPa and Fracture toughness of 8.94 MPa m0.5. This work sheds light on constructing the relationship between the microstructure, mechanical performance of Ti(C,N)-based cermets and the Ni/Co-based binders.