Carbide Grains Research Articles

A new process for preparing ultrafine WC-Co cemented carbide by doping yttrium within the ammonium metatungstate solution

Ultrafine WC-Co cemented carbide has superior performance of high strength and high hardness, which is widely used in industrial fields. In the traditional process, high temperature carburization method is used to prepare tungsten carbide, and solid-phase mechanical milling method is used to mix grain growth inhibitor (Cr3C2) and tungsten carbide, which easily lead to large WC particle size and uneven WC grain size distribution in WC-Co cemented carbide, thus affecting mechanical properties of the alloy. In the new process, based on the genetic relationship between the particle size of ammonium paratungstate and tungsten carbide, ultrafine ammonium paratungstate uniformly doped with yttrium was firstly obtained by adding a certain amount of ammonia and yttrium oxide into the ammonium metatungstate solution. Then the ammonium paratungstate was calcined to obtain yttrium-doped tungsten trioxide, which was then converted into yttrium-doped ultrafine tungsten carbide powders by introducing carbon monoxide at a low temperature. Finally, the ultrafine WC-Co cemented carbide was prepared by pressure sintering. During the neutralization and crystallization process of ammonium metatungstate solution, the yttrium-doped ultrafine ammonium paratungstate (Fischer particle size 8.4 μm) with narrow particle size distribution and regular morphology was prepared. The yttrium-doped ammonium paratungstate was calcined at 500 °C for 90 min in air atmosphere to obtain yttrium-doped tungsten trioxide powder with a Fischer particle size of 4.5 μm and narrow size distribution. Then the yttrium-doped tungsten trioxide and carbon monoxide gas were reacted at 920 °C for 3h to obtain yttrium-doped ultrafine tungsten carbide powder with a Fischer particle size of 0.32 μm and a specific surface area of 4.44 m2/g, and ultrafine WC-Co cemented carbide with tungsten carbide grain size of 0.28 μm was obtained by pressure sintering. The yttrium uniform distributed effectively inhibited the abnormal growth of tungsten carbide grains. Compared with the WC-Co cemented carbide prepared by solid-phase mechanically mixing tungsten carbide powder and chromium carbide, the yttrium-doped WC-Co cemented carbide had a smaller average tungsten carbide grain size and a more homogeneous microstructure. The prepared yttrium-doped WC-Co cemented carbide had a hardness (HRA) of 94.6, a bending strength of 4841 M, and a coercive force of 42.3 KA/c.

Experiments and modeling of microstructural and mechanical behaviors of laser-welded Ni-based superalloy at high temperatures

The performance of welded Ni-based superalloys at high temperatures is essential to be evaluated due to their particular service environment for aero-engines and high-speed aircrafts. The tensile properties and related microstructural evolutions such as the carbide precipitate and grain of a laser-welded Ni-based alloy were experimentally and numerically investigated at different temperatures (20, 300, 500, 800 °C). The results show that at room temperature, the strength of the Base Material (BM) was slightly smaller, with a difference of less than 1%, than the Welded Material (WM), which can be attributed to the more uniformly distributed needle-shaped carbide precipitates in the WM than those nonuniformly coarser spherical ones in the BM. While at 300 °C and 500 °C, the strength of WM decreased more obviously compared with that of BM due to the more apparent growth of grain: 13.52% loss in yield strength in WM alloys as compared with BM alloys at 300 °C, and 16.57% at 500 °C. At 800 °C, the strength of BM and WM both decreased to a similar level due to Dynamic Recrystallization (DRX). However, a much higher elongation was observed for the BM than WM (less than 50% of BM), which can be attributed to the enhanced dislocation accumulation capability of the large spherical carbides along grain boundaries on the fracture surface in BM. Furthermore, a unified model considering the welding effects on both microstructures (dislocation, carbides, and grain) and mechanical properties evolutions at different temperatures was developed and validated. Based on this model, the key temperature ranges (20–600 °C) where apparent weakening of strength and uniform plasticity occurs for welded structures were identified, providing a direct guidance for potential structure and process design.

Eliminating metallurgical defects and achieving strength-ductility combination in selective laser melted martensitic stainless steel through high-pressure annealing

Due to high difficulty in fabricating and processing high-strength metals, additive manufacturing has been considered to have broad prospects compared to the traditional casting means. However, unavoidable metallurgical defects and strength–ductility trade-off dilemma have become Achilles' heels for their practical applications. In this work, one high-pressure annealing (HPA) strategy was introduced to process the selective laser melted (SLM) martensitic stainless steel. The microstructures and mechanical properties of as-built, high temperature annealing and HPA and as-rolled SLM samples were systematically investigated. It was found that the HPA treatment makes the stainless steel achieve the significant yield strength of 1828 MPa and the comparable plastic strain of 36.2% compared to other samples. The pores and laminar structures from the SLM process were eliminated by HPA. What is more, the HPA treatment results in uniform carbide precipitation, grain refinement and nanoscale heterogeneous structure comprising a series of coarse and fine grains. The physical mechanism for nanoscale heterogeneous structure induced by HPA was discussed from the perspective of the cooperative effect of temperature and pressure. Additionally, the strengthening contributions from grain refinement, carbide precipitation, dislocation hardening, heterogeneous structure and pore closure were quantitatively determined. The current study not only reveals the comprehensive effect of temperature and pressure on microstructure and mechanical properties, but also establishes HPA as an effective method to evade the strength-ductility trade-off in alloys fabricated by additive manufacturing.

Microstructural evolution in a one-directional phase transforming ultrahigh temperature ceramic laminate composite

A metal-ceramic multilayer composite composed of Zr and ZrC films was magnetron sputter deposited and annealed at 1325 °C to demonstrate its ability to phase transform into a single phase, substoichiometric ultrahigh temperature ceramic carbide. The pre-annealed laminate microstructure comprised columnar grains for both the Zr and ZrC layers, common to thin film deposition. Upon annealing, the diffusion of carbon facilitated the precipitation of multiple equiaxed carbide grains that consumed the former Zr layers. As this carbon diffused from ZrC, it resulted in the carbide undergoing a lattice contraction where the elastic strains facilitated a decohesion between the carbide grain boundaries. This decohesion is shown to be mitigated by increasing the ratio of the initial ZrC layer-to-Zr layer thicknesses. Finally, oxygen, found to be a minor impurity in the ethylene hydrocarbon gas used to reactively deposit ZrC, facilitated irregular zirconia precipitation within the evolving microstructure during the anneal.

A comprehensive investigation of Kingery type Σ3 (111) grain boundaries in TiC, TaC, and WC

Carbide materials find extensive application as tool materials due to their exceptional properties, encompassing high hardness, wear resistance, and robust strength. Exhibiting diverse bonding characteristics, carbides constitute a pivotal material class in modern-day technologies. The structural and energetic attributes of grain boundaries play a vital role in understanding the properties of polycrystalline materials, necessitating an examination of the grain boundary regime. In this study, metal carbide grain boundaries, specifically the Kingery type Σ3 (111) grain boundaries in TiC, TaC, and WC, were systematically investigated utilizing density functional theory calculations. The scrutiny comprehends their structural, electronic, mechanical, and thermal properties. Results show that the investigated grain boundaries are energetically stable. The calculated electronic properties further unveil the presence of metallic behavior. Dynamic stability was observed at 0 K for Σ3 (111) grain boundaries constructed from the L10 cubic lattice structure in TiC, while phonon softening was observed for the Σ3 (111) grain boundaries structures in TaC and WC. Thermodynamic properties, including Helmholtz free energy, heat capacity, and entropy, were thoroughly scrutinized. Mechanical properties suggest the ductile behavior with significant metallic nature of considered grain boundary systems. The study extended to thermal properties, examining the lattice thermal conductivity (κL) of the considered grain boundary systems. It was observed that the Σ3 (111) grain boundary in TiC significantly increases the thermal conductivity.

Flexible CNT-based composite films with amorphous SiBCN-inhibited ultrafine SiC grains for high-temperature electromagnetic shielding

Lightweight, flexible and highly conductive electromagnetic interference (EMI) shielding materials are of great importance for protecting flexible electronics and telecommunication devices under extremely high temperature conditions. A potential solution is to incorporate ceramic phases with highly conductive flexible carbon nanotube films to improve their thermal stability. However, the grain size of the ceramic phase generally increased significantly as the temperature increased which led to brittleness. In this work, a highly flexible carbon nanotube (CNT) film with controllable ceramic nanocrystals was prepared by precursor infiltration and pyrolysis. The silicon carbide (SiC) grain size in the nanocomposites was inhibited by the spatial confinement effects of CNT networks and a second amorphous SiBCN phase. The SiC grain size in the composite film decreased with the increase of the SiBCN content and the elongation at break of the nanocomposites improved significantly by 45 %. Moreover, the initial thermogravimetric temperature of the prepared films has been significantly improved to exceed 600 °C compared to the raw CNT film. Importantly, the nanocomposite film exhibited an average EMI shielding effectiveness of ∼40 dB from 8.2 to 12.4 GHz. Benefiting from the ultrafine grain size, the nanocomposite films could be folded and extended without micro-cracks over 1000 times. Combining the performance and mechanical properties of the nanocomposite film, this approach provides important guidance for designing high-performance CNT-based electromagnetic shielding materials with superior flexibility at elevated temperatures.

Isotope studies of presolar silicon carbide grains from supernovae: new constraints for hydrogen-ingestion supernova models

ABSTRACT We report isotope data for C, N, Al, Si, and S of 33 presolar SiC and Si3N4 grains (0.3–1.6 $\mu$m) of Type X, C, D, and N from the Murchison CM2 meteorite of likely core-collapse supernova (CCSN) origin which we discuss together with data of six SiC X grains from an earlier study. The isotope data are discussed in the context of hydrogen ingestion supernova (SN) models. We have modified previously used ad-hoc mixing schemes in that we considered (i) heterogeneous H ingestion into the He shell of the pre-SN star, (ii) a variable C-N fractionation for the condensation of SiC grains in the SN ejecta, and (iii) smaller mass units for better fine-tuning. With our modified ad-hoc mixing approach over small scales (0.2–0.4 M⊙), with major contributions from the O-rich O/nova zone, we find remarkably good fits (within a few per cent) for 12C/13C, 26Al/27Al, and 29Si/28Si ratios. The 14N/15N ratio of SiC grains can be well matched if variable C-N fractionation is considered. However, the Si3N4 isotope data point to overproduction of 15N in hydrogen ingestion CCSN models and lower C-N fractionation during SiC condensation than applied here. Our ad-hoc mixing approach based on current CCSN models suggests that the O-rich O/nova zone, which uniquely combines explosive H- and He-burning signatures, is favourable for SiC and Si3N4 formation. The effective range of C/O abundance variations in the He shell triggered by H ingestion events in the massive star progenitor is currently not well constrained and needs further investigation.

Protective layers of zirconium alloys used for claddings to improve the corrosion resistance

Abstract Zirconium alloys are used as a cladding material for fuel elements in nuclear reactors. In the case of severe accident conditions, the possible rapid oxidation of zirconium in steam or/and air may result in intense hydrogen generation and hydrogen–oxide mixture explosion. Advanced technologies for increasing the corrosion resistance of claddings are being investigated in two directions: (a) protective coatings on Zr alloys and (b) the use of new materials for claddings. Coatings with silicon may provide a more protective barrier than the ZrO2 films formed on an alloy cladding during nuclear plant operations. These coatings may also serve as a protective barrier during high-temperature accidents. The current work aimed at developing protective coatings with silicon on zirconium alloys. Multielemental Zr–Si–Cr coatings were formed on Zry-2 alloy using the physical vapor deposition (PVD) method. Long-term oxidation tests were carried out under the following conditions: 360°C/195 bar/63 days/water-simulating PWR water. Obtained results show the protective character of formed layers. The material in the form of silicon carbide grains covered with yttrium–aluminum garnet (SiC + YAG) was prepared using the sol–gel method. The formed powder is the main component for coating formation on Zr–1Nb alloy using the method of suspension plasma spraying (SPS).

Effect of binder phases on the microstructure and sliding wear properties of HVOF-sprayed WC-based coatings

This study aimed to evaluate the microstructure and wear properties of WC-10Co-4Cr, WC-12Co, and WC-17Co coatings on TC4 titanium alloy. The coatings were deposited using high velocity oxygen-fuel (HVOF) technique. To analyze the influence of binder phases, the coatings were thoroughly examined using scanning electron microscopy, X-ray diffractometer, microhardness tester, and friction and wear tester. The analysis of the results reveals that the primary phases in all three coatings consist mainly of WC, with smaller quantities of W2C and amorphous phases present. The WC-10Co-4Cr powder demonstrates a relatively even particle size distribution, high degree of sphericity, and rough porous surface, allowing for efficient heat absorption and uniform heat distribution, resulting in a dense coating. Notably, the WC-10Co-4Cr coating exhibits significantly smaller tungsten carbide grain size compared to the other coatings. Moreover, the microhardness of the WC-10Co-4Cr coating, measured at 1377.8 HV0.05, is significantly higher than that of the WC-12Co and WC-17Co coatings, which measured at 1258.8 HV0.05 and 1182.4 HV0.05, respectively. Additionally, the WC-10Co-4Cr coating demonstrates low friction coefficient and wear volume, indicating excellent wear resistance. Subsequently, a comprehensive analysis was conducted to determine the reasons for the relative enhancement in binder performance.

Investigation of the Corrosion and Tribological Properties of WC-Co Tools Hardened with PVD Coatings in Solid Oak Wood Processing

Corrosion and friction coefficient tests were performed on solid oak wood machined with hard-metal woodworking tools coated with PVD coatings (AlCrN, AlTiN, TiAlN, TiCN and CrN). The tannic acid attacks the carbide more intensively than the PVD coatings. During cutting, corrosion spreads on the cutting edge of the cutter due to mechanical action, which dissolves the cobalt binder of the hard-metal and causes the carbide grains to flake off. After 80 min of contact with the wood, the cobalt content decreases from 3.53 to 1.74%. Depending on the PVD coating material, cracks of 4 to 40 µm in width appear after 120 min (9000 m cutting path). After 120 min of machining, wear, corrosion effects and the influence of corrosion on the coefficients of friction were evaluated for tools with and without PVD coatings. TiCN is the most sensitive to corrosion, while AlCrN and CrN coatings are the least sensitive, with the AlTiN coating being the most affected under real cutting conditions (with mechanical + thermal + corrosion effects) and the tools with CrN and AlCrN coatings being the least affected. Corrosion affects the hard-metal and PVD coatings and reduces the coefficient of friction. The angle between the directions of sliding and sharpening of the cutting edge sharpening significantly influences this parameter. The coefficient of friction of hard-metal WC-Co and PVD coatings is higher in the parallel machining direction than in the perpendicular machining direction and ranges from 16.03% (WC-Co) to 44.8% (AlTiN). The coefficient of friction of hard-metal WC-Co decreases by 5.13% before and after exposure to tannic acid, while the corrosion of PVD coatings reduces it by 4.13% (CrN) to 26.7% (TiAlN).

Highly Active W2C-Based Composites for the HER in Alkaline Solution: the Role of Surface Oxide Species.

The hydrogen evolution reaction (HER) is a crucial electrochemical process for the proposed hydrogen economy since it has the potential to provide pure hydrogen for fuel cells. Nowadays, hydrogen electroproduction is considerably expensive, so promoting the development of new non-noble catalysts for the cathode of alkaline electrolyzers appears as a suitable way to reduce the costs of this technology. In this sense, a series of tungsten-based carbide materials have been synthesized by the urea-glass route as candidates to improve the HER in alkaline media. Moreover, two different pyridinium-based ionic liquids were employed to modify the surface of the carbide grains and control the amount and nature of their surface species. The main results indicate that the catalyst surface composition is modified in the hybrid materials, which are then distinguished by the appearance of tungsten suboxide structures. This implies the action of ionic liquids as reducing agents. Consequently, differential electrochemical mass spectrometry (DEMS) is used to precisely determine the onset potentials and rate-determining steps (RDS) for the HER in alkaline media. Remarkably, the modified surfaces show high catalytic performance (overpotentials between 45 and 60 mV) and RDS changes from Heyrovsky-Volmer to Heyrovsky as the surface oxide structures get reduced. H2O molecule reduction is then faster at tungsten suboxide, which allows the formation of the adsorbed hydrogen at the surface, boosting the catalytic activity and the kinetics of the alkaline HER.

The effect of carbide decomposition and carbon loss on the steady state composition of WC-Cr3C2-Ni composite coatings at 900 °C.

The steady-state composition and microstructure of 42 wt% WC-42 wt% Cr3C2–16 wt% Ni coatings sprayed under “low”, “medium” and “high” thermal input conditions was explored following treatment at 900 °C for up to 30 days. None of the coatings achieved thermodynamic equilibrium compositions. Attempts at compensating for mechanisms of bulk carbon loss and selective carbon loss from the dissolution phases alone, were both unsuccessful in predicting the steady-state compositions based on equilibrium phase diagrams. The low thermal input HVOF coating underwent recovery of the dissolved Cr3C2 phase to form an interconnected, two-phase Cr3C2 + Ni-alloy matrix surrounding the retained WC grains, which did not achieve thermodynamic equilibrium with the precipitating phases. The high carbide dissolution plasma ArH2 coating generated a homogeneous distribution of metallic and carbon elements such that the metal: carbon ratio exceeded 1:1, favouring the formation of (W,Cr)2C. The remaining material formed (Cr,W)3C2 within a Ni(Cr,W) alloy binder. Chromium stabilised the (W,Cr)2C phase such that it did not decompose into W + WC, as predicted in the WC system. The plasma ArHe response was a mix of these mechanisms. A distinctive feature of the heat-treated coatings was the lack of significant grain growth, with submicron carbide grains retained out to 30 days at 900 °C.

High-temperature sliding wear performance of HVAF sprayed WC-based coatings with alternative binders

The wear performance of HVAF sprayed WC-based composite coatings with Co-lean or Co-free binders was evaluated as an alternative to conventional WC-CoCr wear-resistant layers. The coatings were characterized for microstructure and tested for their micro and nano hardness. Their tribological behavior was studied for reciprocating sliding wear at room and elevated temperature (∼300 °C). Using nanoindentation, the hardness of carbide grains was measured to be between 18 GPa and 25 GPa. Nanoindents that fell in the binder phases had a hardness of 15 GPa–18 GPa, which, due to the fine scale of the microstructure, represents some average mixture of the binder and carbide. Using Vickers indentation at higher loads, the hardness values of the coatings at room temperature were found to be between 1000 and 1200 HV0.3, which decreased by ∼200 HV0.3 when tested at elevated temperatures. The wear performance of all coatings with alternative binders at room temperature was comparable to that of the reference WC-CoCr. However, the specific wear rates of the coatings tested at elevated temperature was higher by 1–2 orders of magnitude compared to those performed at room temperature. With the exception of WC-FeNiCrMoCu, the other three coatings exhibited comparable high-temperature wear performance. Ripple-like patterns were the prominent feature observed on the room temperature wear tracks. At elevated temperatures, wear tracks showed macro cracking and micro fatigue cracks, as well as pitting and oxide formation on the surface of wear track.

The Presolar Grain Database. I. Silicon Carbide

The Presolar Grain Database (PGD) contains the vast majority of isotope data (published and unpublished) on presolar grains and was first released as a collection of spreadsheets in 2009. It has been a helpful tool used by many researchers in cosmochemistry and astrophysics. However, over the years, accumulated errors compromised major parts of the PGD. Here, we provide a fresh start, with the PGD for silicon carbide (SiC) grains rebuilt from the ground up. We also provide updated rules for SiC grain type classification to unify previous efforts, taking into account newly discovered grain types. We also define a new grain type D, which includes some grains previously classified as ungrouped. Future work will focus on rebuilding the PGD for other kinds of presolar grains: graphite, oxides, silicates, and rarer phases.

Combustion synthesized boron carbide powders by different organic carbon sources and microwave absorbing properties

AbstractBoron carbide powders were synthesized by combustion synthesis using organics chitosan, dextrin, cellulose, starch, and polyvinyl chloride (PVC) as carbon sources. The microwave absorbing properties of boron carbide powders synthesized by different carbon sources were investigated. The results showed that the powders synthesized using organic compounds containing Cl and N atoms as carbon sources have better absorbing properties. The peak value of reflection loss of boron carbide powder prepared with chitosan as carbon source is −46.41 dB at 2.1 mm thickness, with an effective absorption range of 9.21–12.30 GHz and an effective absorption bandwidth of 3.09 GHz. The small and uniform boron carbide grains and residual carbon with multiple morphologies enhance the interface polarization and electronic polarization in the material, which leads to multiple reflections and losses of the microwave. Additionally, the lattice defects and surface holes caused by Cl, N, and other atoms in chitosan and PVC increase the energy storage sites of the material, which makes the materials obtain excellent microwave absorbing properties. Boron carbides fabricated from an organic carbon source provide a potential for the preparation of high‐temperature resistant absorber.

Hybrid composite with WC/Y–TZP–Al2O3 ceramic matrix and dispersed Hadfield steel particles

Low-temperature and short-time sinter-forging has been used to obtain a dense WC/Y–TZP–Al2O3 hybrid ceramic–matrix composite with dispersed Hadfield steel with high fracture toughness. The hardness and К1С fracture toughness were 13.7 ± 0.3 GPa and 7.4 ± 0.4 MPa m1/2, respectively. The composite contained phases such as Y–TZP–Al2O3 eutectics and hypereutectic grains, WC agglomerates, γ-Fe particles as well as small amounts of Al2(WO4)3 and MnFe2O4. No t-ZrO2→m-ZrO2 transformational toughening occurred during mechanical loading so that enhanced fracture toughness resulted from forming a dense microstructures with ductile metallic interlayers between ceramic and tungsten carbide grains.

Wear characteristics of dual‐phase high‐entropy ceramics: Influence of the testing method

AbstractWear behavior of a fine‐grained dual‐phase high‐entropy carbide/boride ceramics was investigated using ball‐on‐flat dry sliding methods in air, applying rotational and linear reciprocation motion with SiC counterpart. The investigated system showed very high nanohardness of the carbide and boride grains with mean values of 37.4 ± 2.3 and 43.0 ± 2.9 GPa, respectively, with the microhardness of dual system HV1 29.4 ± 2.0 GPa. The stabilized friction coefficient values during the circular tests changing from .62 to .77. During the reciprocal test, the frictional coefficient values are very similar with an average value of .53. The specific wear rates during the circular motion were similar in the range from 4.65 × 10−7 to 1.68 × 10−7 mm3/N m. During the reciprocal test, the wear rates at 5 and 25 N were similar as in the case of circular motion, but at 50 N load, the wear rate increased significantly to the value of 9.11 × 10−6 mm3/N m. The dominant wear mechanisms in all cases were oxidation driven tribochemical reaction and tribolayer formation in boride grains and mechanical wear in carbide grains. During the linear reciprocation test, the loading mode created conditions resulted in relatively low coefficient of friction and very high specific wear rate.

Dual-phase high-entropy carbide/boride ceramics with excellent tribological properties

Tribological characteristics of fine-grained dual-phase high-entropy carbide/boride ceramics were investigated using the ball-on-flat dry sliding method in air, applying linear reciprocation motion with SiC counterpart. Detailed fractographical analyses were used for the characterization of the deformation and damage mechanisms. The investigated system with composition (Ti0.14Zr0.2Nb0.2Hf0.2Ta0.26)C + (Ti0.38Zr0.18Nb0.22Hf0.115Ta0.105)B2 showed density with value 8.72 g/cm3 and very high hardness of HV1 29.4 ± 2.0 GPa. The friction coefficient at the test with 5 N was 0.56 and during the test with 10 N and 25 N loads were 0.48 and 0.5, respectively. The effective wear rates at the loads of 5 N and 25 N were very similar with values of 7.93 × 10−7 mm3/Nm and 6.63 × 10−7 mm3/Nm. At load 50 N the effective wear rate is significantly higher with a value of 9.11 × 10−6 mm3/Nm. Detailed fractography revealed that the dominant wear mechanisms at loads of 5 N and 25 N were an oxidation-driven tribochemical reaction and tribo-layer formation in boride grains and mechanical wear in carbide grains and at the load of 50 N fracture of boride and carbide grains and formation of chemically complex tribolayers.

Microstructural evolution and mechanical properties of Ti(C,N)–FeCrMo-based green cermets

This work aims to develop Co and Ni-free Ti(C,N)–Fe-based cermets which are essential for developing cermets in the direction of green and low-cost materials. TiC and Ti(C,N) -based cermets prove to evince excellent mechanical properties at high temperatures as compared to conventional WC-based cermets. A binder system based on Cr, Mo, Fe, and their alloys may offer a viable solution to replace carcinogen elements such as Ni and Co from the binder. In the present work, high chromium Ti(C,N)-30 wt% FeCrMo cermets were fabricated by using Pressureless liquid-phase sintering. Samples at different sintering temperatures were prepared to investigate the influence of the temperature on microstructural formation and their mechanical characteristics. Scanning Electron Microscopy (SEM) is employed to observe the microstructural formation. A microstructural analysis of the consolidated cermets reveals that the addition of Mo to the binder system and an increase in sintering temperature affect the carbide grain size and densification, which ultimately affect their mechanical characteristics. The hardness and fracture toughness were determined by the Vickers hardness test and Indentation fracture toughness (IFT) method respectively. The maximum Hardness, Fracture toughness, and Transverse rapture strength achieved for the Ti(C,N)–FeCrMo-based green cermets are 665 ± 6.7 MPa, 1396 ± 26 HV30, and 9.23 ± 0.12 MPa m1/2 respectively.

Postprocessing of tungsten carbide‐nickel preforms fabricated via binder jetting of sintered‐agglomerated powder

AbstractThis study binder jets a tungsten carbide‐nickel (WC‐Ni) sintered‐agglomerated composite powder, and postprocesses the preforms using an initial sintering step followed by a hot isostatic pressing (HIP) step. The effects of sintering temperatures, sintering durations, and HIP temperatures on notable properties (e.g., porosity, microstructure, hardness, and oxidation behavior) are quantified. The highest average relative density produced in this study was 96.8%, and volumetric shrinkage of these coupons was about 64%. Microstructural characterization shows that the WC grains are homogenously distributed throughout the nickel matrix and grow to an average diameter of 1.6 (a 60% increase) during processing. X‐ray diffraction patterns indicate that no unwanted products were formed. Processed coupons achieved a maximum hardness of 54 Rockwell C, limited by their internal porosity. Oxidation tests result in the production of WO3 and NiWO4 at temperatures above 600°C. Methodologies and results from this study can be leveraged to additively manufacture highly dense, geometrically complex WC‐Ni parts with small carbide grains, low nickel content, desirable microstructure, and suitable functional properties.