NbC Content Research Articles

The microstructure evolution and mechanical properties of WC-cu-10Ni-5Mn-3Sn cemented carbides containing NbC prepared by pressureless melt infiltration

WC-based cemented carbides with different contents of NbC (0, 0.6, 0.8, 1.0, 1.2, and 1.4 wt%) are prepared via pressureless melt infiltration at 1200 °C for 1.5 h. Microstructure evolution regularity of WC-based cemented carbide is investigated to establish the effect of NbC addition and microstructure peculiarities on mechanical properties (flexural strength, hardness, and impact toughness) of final product. Experimental results reveal that NbC firstly dissolves in binder alloy during melt infiltration, which slows down dissolution-precipitation reaction of WC, thus refining WC grains. With the increase in NbC content, average WC grain size shows varying trend, achieving the minimum (3.779 μm) at NbC addition of 1 wt%. When NbC is added in smaller amounts, Nb is mainly distributed throughout binder alloy. With the increase in NbC content, Nb elements tend to form aggregates and attach to WC particle boundaries. Some WC and NbC also decompose under experimental conditions. At NbC addition greater than 1 wt%, decomposition products (Nb, W, and C) combine with other elements in binder phase to form new phases such as (Nb,W)C, Ni2W4C, Nb2C, and Nb4Ni2C. These phases further act as bridges for WC grain coarsening. Meanwhile, excessive NbC is detrimental to mechanical properties of the alloy. With the increase in NbC content, hardness and flexural strength of the alloy increase and then decrease, reaching the maximum values of 93.4 HRA and 1808.786 MPa, respectively, at 1 wt% NbC addition. In turn, impact toughness of the alloy shows consistently downward trend. Therefore, changes in mechanical properties of WC-based cemented carbides are mainly related to WC grain size, the appearance of new phases in binder phase, and their morphology.

Effect of in-situ NbC content on the microstructure and mechanical properties of Ni625 composite coating by laser cladding

To improve the mechanical properties of Ni625 coatings, different contents of Nb powder and Ni-coated graphite particles were added to Ni625 powder for in-situ generation of NbC particles. The effects of different NbC contents on the microstructure, hardness, wear resistance and corrosion resistance of Ni625 coatings were investigated. The results show that the highest XRD phase diffraction peaks of NbC in the coating are obtained with the addition of 15 % (Nb 9.9 %, Ni-coated graphite particles 5.1 %), and the coating exhibits a hardness of 441.9 HV, which is 1.53 times greater than that of the coating with the addition of 0 %. Furthermore, the wear coefficient (μ) of the coating is 0.4804, and the wear volume is 0.0042 mm3, representing a reduction of 23.5 % and 64.1 %, respectively, in comparison to the coating with 0 % additive. However, the coating with an addition of 20 % does not generate more NbC phase, and the hardness and wear resistance are not further improved. The coating with an addition of 10 % has the best corrosion resistance, with a corrosion current density of 2.1829E-10 A/cm2. Further additions do not result in an enhanced corrosion resistance of the coating. Therefore, appropriate amount of in-situ generation of NbC within the Ni625 coating during the laser cladding process can effectively enhance the mechanical properties of the Ni625 coating.

Microstructure evolution, wear and corrosion behaviour of (Nb, V)C-reinforced Fe-based composite coatings by laser cladding

Five Fe-based composite coatings with different weight ratios of Nb were prepared by laser cladding on 0Cr13Ni5Mo substrate. As the Nb content imposes, the NbC content gradually increases; the microstructure was refined; and the NbC morphology changed from quadrangle carbides to petaloid and papilionaceous carbides. Meanwhile, the microhardness and wear resistance of the composite coating gradually improve. The S3 coating exhibited a high microhardness of approximately 610 ± 12.2 HV and an excellent wear resistance. The S3 coating showed the highest corrosion resistance in 3.5 wt-% NaCl solution with Ecorr and Icorr of −179.3 mV and 9.258 × 10−8 A/cm2, respectively. The improvement in the corrosion resistance could be attributed to the fact that the forming NbC would consume amounts of C in the matrix; thus, the Cr atoms were released from its carbide state, and then dissolved in the matrix.

Microstructural evolution and interfacial properties of explosively welded Nb/steel composite plate during post-heat treatment

In this work, Nb/steel composite plates were fabricated by explosive welding technique. Then post-heat treatments were conducted for large temperature range of 723 K–1273 K. Microstructural evolution and interfacial properties in welded interface were revealed by SEM, EBSD, XRD, microhardness, nanohardness and shear strength examinations. The effects of annealed temperature on interfacial microstructures and properties of Nb/steel composites were systematically investigated. The results demonstrated that microstructures and microhardness of Nb-side almost presented no changes with annealed temperature; Carbon elements from steel-side diffused easily into Nb-side forming a thin Nb carbide layer in which content of NbC increased as increasing annealing temperature; At 1273 K, formation of Nb2C was also found in carbide layers. In the steel-side, during low temperature (723 K–923 K) annealing, the deformed pearlite near interface recrystallized to form ferrite of which grains grew up with increasing annealed temperature; During high temperature (1073 K–1273 K) annealing, a large number of voids appeared at 1073 K, and typical normalizing structure generated at 1173 K–1273 K. Meanwhile, it was also found that with increasing of annealed temperature, shear strength firstly increased to maximum value of 326 MPa at 923 K and then decreased to 267 MPa at 1273 K. Failure mechanism of shear tests exhibited mixed ductile-brittle fracture at low temperature annealing; Then it converted into brittle fracture at high temperature annealing. Microhardness near interface of steel side firstly decreased to the minimum value of 106HV at 923 K and then increased to value of 220HV at 1273 K.

Hydrogen embrittlement sensitivity of dispersion-strengthened-high-strength steel welded joint under alternating wet-dry marine environment

This paper investigated the effects of welding and alternating wet-dry seawater on the hydrogen embrittlement (HE) susceptibility of a new nanoparticle-reinforced high-strength steel, dispersion-strengthened-high-strength (DSHS) steel. The results show that welding led to the transformation of granular bainite to tempered martensite. It also promotes grain coarsening as well as an increase in inclusions size and irregular changes in shape. This results in increased susceptibility to HE at the welded joint (WJ). After wet-dry cycle corrosion in seawater, corrosion products impede the oxygen transfer and promote the hydrogen evolution reaction, so the hydrogen production increases. The decrease in the protection of corrosion products at the WJ and the decrease in NbC content led to an increase in hydrogen production but a decrease in hydrogen trapping capacity. Therefore, the WJ HE sensitivity of DSHS steel is further increased.

A novel NbC/CrMnFeCoNi0.8 high entropy alloy matrix composites with ultrastrength and ductility: Experiments and density function theory

In this work, NbC particle-reinforced CrMnFeCoNi0.8 high-entropy alloys (HEAs) matrix composites were prepared by induction melting method. With increasing NbC content, the strength of the composites increases first and decreases afterwards, while the ductility decreases monotonically. The composite with 5 vol% NbC exhibits an excellent combination of yield strength (458.9 MPa), ultimate tensile strength (917.9 MPa), and ductility (29.0% elongation). The enhanced strength of the composite can be attributed to the synergy of various strengthening mechanisms, including dislocation strengthening, Orowan strengthening and load-bearing effect. Density functional theory (DFT) calculations revealed that the addition of NbC particles increases the value at Fermi level for individual elements in the HEA matrix, which provides support for improving mechanical properties of the NbC-reinforced composites.

Properties of NbC/а‐C:H films on titanium bipolar plates for proton exchange membrane fuel cells

AbstractSurface modification of metallic bipolar plates is a crucial subject for the performance elevation of proton exchange membrane fuel cells (PEMFCs). In this work, a series of NbC/а‐C:H films with different Nb/C ratios are prepared by arc ion plating. Film microstructure, composition, mechanical properties, hydrophobility, interfacial contact resistance (ICR), and corrosion resistance in the simulated cathode environment of PEMFCs are systematically studied. The results show that within the experiment conditions, higher NbC content helps to promote the film hardness and adhesion strength as well as the interfacial conductivity. While higher а‐C:H content attributes to a more compact microstructure thus improving the anti‐corrosion performance. The best corrosion resistance and conductivity come with the lowest corrosion current density of 0.09 µA/cm2 and ICR of 0.77 mΩ cm2, respectively. Based on the result of this research, to further improve the comprehensive performance of NbC/а‐C:H film, strategies for increasing the metal carbide content and preventing surface metal oxidation while keeping a dense and fine microstructure need to be considered.

Influence of reduced carbon content on microstructure and mechanical behavior of Inconel 718 prepared by laser powder bed fusion

• Successful production of a reduced carbon Inconel 718 alloy via SLM. • Significant changes in the precipitation behavior of NbC and γ’’ are achieved. • Reductions in NbC content and finer γ’’ precipitation verified By Thermocalc. • Reduced γ’’ size results in improved tensile strengths at both 25 °C and 650 °C. Inconel 718 powder with reduced carbon content was used to manufacture coupons via laser powder bed fusion (LPBF) to study the influence of carbon content on microstructures and mechanical properties of HIP'ed and heat-treated material. The carbon concentration in this material was kept deliberately low (0.01 wt%) relative to a typical commercial powder composition (0.04 wt%) of IN718 in order to minimize the precipitation of primary carbides during post-processing heat treatments, which have been observed to be deleterious to elevated temperature mechanical properties such as elongation, stress rupture ductility, and notch sensitivity. The final microstructure of the lean C alloy is shown to have a significantly reduced NbC population relative to the baseline material. Furthermore, other microstructural variations such as an increased δ phase population and decreased γ’’ particle size were observed. Empirical observations agreed with microstructural simulations calculated by the ThermoCalc/TC-PRISMA precipitation module. These changes to the microstructure resulted in a 10% increase in the yield strength at both 25 and 650 °C in the lean C alloy, bringing the strength of LPBF-printed material closer to that of wrought IN718. Overall, the reduction in carbon content in the raw material has significant effects beyond limiting the pre-solution treatment precipitation of NbC, primarily by freeing Nb for formation of δ and γ’’ phases.

Consolidation and high‐temperature properties of ceramics in the TaC–NbC system

AbstractIn this study, we explored the consolidation, solid‐solution formation, and high‐temperature properties of carbides in the Ta–Nb–C system. The tantalum niobium carbide bulks can be consolidated by spark‐plasma sintering only at a temperature of 2200°C using a 30‐min dwell. The ceramics were homogeneous solid solutions and a linear dependence of the lattice parameters on the NbC content was observed. The average grain size varied between 10 and 30 μm, while the reference monolithic tantalum carbide consolidated under similar conditions had a grain size exceeding 40 μm. The room temperature strength linearly decreased from TaC to NbC. The 75 mol% NbC ceramic showed almost an unchanged strength up to 1600°C (450 ± 20 MPa), following the linear decrease in strength to 290 MPa at 2000°C. The monolithic tantalum carbide had showed the lowest strength at 2000°C among the studied ceramics.

Effects of Nb and NbC additives on microstructure and properties of WC-Co-Ni cemented carbides

Cemented carbides (WC-Co-Ni) with the addition of Nb and NbC respectively were prepared by the conventional powder metallurgy method. The microstructure and mechanical properties of the sintered samples were analyzed. The results indicated that the addition of Nb or NbC reduced the grain size of WC and Nb had a greater inhibition effect on WC grain growth than NbC. The transverse fracture strength of the samples first increased and then decreased with the increase of the amount of Nb and NbC, and reached 3120 MPa and 2850 MPa respectively when adding 1.0 wt% Nb and NbC. The hardness of cemented carbides showed an upward trend as the content of additives increased. The fracture toughness decreased with the increases of NbC and Nb contents respectively and the fracture toughness of NbC-added samples was lower than that of Nb-added samples. The impact toughness decreased in a mass with the increase of additives.

Effects of NbC content on microstructural evolution and mechanical properties of laser cladded Fe50Mn30Co10Cr10-xNbC composite coatings

In this paper, NbC reinforced Fe50Mn30Co10Cr10 high entropy alloy coatings with different NbC content were fabricated by laser cladding. The formation mechanism of NbC particles with micro/nano-scale was analyzed. Based on the interaction between the solid-liquid interface and NbC particles, the distribution of micro/nano-scale NbC particles is clarified. The effects of NbC content on microstructure and mechanical properties of the coatings were investigated. It demonstrated that the nanoscale NbC particles restricted the dendritic growth whilst promoting grain nucleation and altering the grain morphology from columnar grain to equiaxed dendrite. Besides, the influence of NbC particles on FCC phase stability was studied based on the lattice mismatch theory, which indicates that the addition of ceramic particles is a new way to modify the phase volume fraction in the dual-phase high-entropy alloys (HEA). The micro-hardness and wear resistance of the coatings significantly improved with the increase of NbC content. For the Fe50Mn30Co10Cr10-30 wt%NbC high entropy composite coating, the average Vickers hardness and friction coefficient value separately is 525 HV and 0.45. In addition, the large fluctuations on the friction coefficient of the coatings for 10 wt% and 20 wt% NbC addition may be related to the uneven distribution of nanoscale NbC particles in the matrix.

Effects of High Carbon Ferrochrome Additions on the Microstructure and Properties of Fe-C-Cr-Nb Hardfacing Alloys

Fe-Cr-C-Nb hardfacing alloys composed of 1.07-1.33 wt% C, 0.08-2.61 wt% Cr, and 4.55-4.98 wt% Nb were prepared on C45E4 steel surfaces using alloy steel flux-cored wires. The alloy microstructures were studied by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) and the effects of the alloying elements on the hardfacing properties were determined. The results indicate that these alloys contain martensite, austenite and NbC phases. As the C，Cr and Nb mass fraction in the surfacing material increases, the austenite and NbC contents increase, and the martensite content decreases. The NbC crystallite size in the surface layer affects its hardness and thus its wear resistance. The wear resistance first increases and reaches to its maximum value which is 5.7 times higher than that of the C45E4 steel substrate, while by higher increasing of the mentioned elements, it decreases.

Influence of NbC Content on the Wear Resistance of Alumina/Niobium Carbide Tools

Wear resistance is a fundamental property which defines the lifetime of cutting tools, but the investigation of wear performance of alternative hard materials for traditional WC-Co composites are recent. The present work evaluated the pin-on-disk wear behavior and mechanical properties, i.e., hardness and fracture toughness of spark plasma sintered Al2O3 matrix composites with additions of 5, 15, 25 or 30%wt of niobium carbide NbC. The wear resistance was observed to increase as a function of the NbC content, even though the hardness reached a plateau at 25%wt NbC. The composite behavior was compared to that of other alumina composite tool materials proving to be a promising material for applications such as ceramic cutting tools. The composition A95N5 presented the best combination of values of wear rate: 8.9 mm3/N.m, hardness equal to (17.36±1.72) GPa and fracture toughness of (3.2±0.6) MPa. m1/2.

Microstructure and wear behavior of spherical NbC hardmetals with nickel-based binders on AISI 4145H steel

To investigate the effect of spherical NbC particles on the wear resistance of nickel-based coatings, five groups of samples were tested. The microstructure of nickel-based coatings reinforced by spherical NbC particles was examined through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The wear behavior of samples was analyzed by microhardness, coefficient of friction, 2D profile across the wear track and summary of tribological properties, respectively. The results shows that in the microstructure of nickel-based coatings reinforced by spherical NbC particles, γ-Ni solid solution and Cr23C6 dominated the coating, and complex carbides (NbC, Cr7C3 and a small amount of Cr3C2) and borides (Cr2B) were also detected. The hardness of the nickel-based coating was 400HV0.2. With the increase of the NbC content in the coating, the hardness gradually increased, reaching the maximum when the content was 40% NbC, which was 610HV0.2. The average friction coefficient of AISI 4145H steel was 0.473, and the average friction coefficient of nickel-based coating was 0.573. With the increase of NbC content in the coating, the friction coefficient of the coating gradually decreased, reaching the lowest at a NbC content of 40%, which was 0.470. Although the friction coefficient of the coating changed slightly with the addition of NbC, in the friction and wear of the nickel-based coating, the coating was adhesively worn, and there were many abrasive dust, scratches and grooves on the surface of the coating. By the way, there were only a few scratches on the surface after friction and wear of the nickel-based coating containing 40% NbC. The wear rate of the coating with 40% NbC content was about 1.6% of AISI 4145H steel or one-tenth of the nickel-based coating.

Microstructures and mechanical properties of in-situ FeCrNiCu high entropy alloy matrix composites reinforced with NbC particles

A series of NbC/FeCrNiCu high entropy alloy matrix composites (2.5, 5, 7.5 and 10 vol% of NbC) were prepared by vacuum induction melting. The microstructures and mechanical properties of the composites were investigated using X-ray electron diffraction, scanning electron microscopy, transmission electron microscopy, tensile and hardness tests. The results show that the FeCrNiCu high entropy alloy matrix composites are composed of FCC solid solution embedded with NbC particles. A coherent relationship was identified between the alloy matrix and reinforcement phase. The formation of NbC particles increases the hardness from 337.6 HV to 591.3 HV. Moreover, compared with the base alloy, the tensile yield strength, ultimate tensile strength and ductility of the new composite first increases and then decreases with the increase of NbC content. The tensile yield strength, ultimate tensile strength and ductility reaches maximum for the composites containing 5 vol% of NbC, which is 458.2 MPa, 691.6 MPa and 24.7%, respectively. The strengthening mechanisms of the composites are discussed and the contributions of dislocation strengthening, load bearing effect and Orowan mechanism are quantified.

Effect of NbC on the microstructure, mechanical properties, and oxidation resistance of Ti(C,N)-based cermets

Abstract A comprehensive investigation of the effects of NbC on the microstructure and properties of Ti(C,N)-based cermets has been performed. Cermet samples were obtained via liquid-phase sintering under the guidance of thermodynamic calculations, and the amount of NbC was varied. The results showed that when the NbC content exceeded 12 wt.%, a hard phase with an NbC core appeared due to the lattice mismatch between the core and rim. NbC was not completely consumed by dissolution and precipitation, causing it to form a residual NbC core. As the NbC content increased, the grain size was refined, and the hardness of the cermet increased, but the fracture toughness decreased. When NbC was introduced into the cermet, a relatively dense protective layer was formed on the surface during oxidation, which restricted the diffusion of oxygen and improved the oxidation resistance of the cermet.

Effect of Nb Content on the Microstructure and Wear Resistance of Fe-12Cr-xNb-4C Coatings Prepared by Plasma-Transferred Arc Welding

The Fe-Cr-C coatings with different levels of Nb addition were prepared on carbon steel by a plasma transferred arc (PTA) weld-surfacing process and their microstructure and properties were investigated. As the Nb content increases from 8.96% to 12.55%, the coating gradually changes from a hypereutectic structure (martensite, austenite matrix, primary NbC and eutectic γ+M7C3) to a near eutectic structure (γ+M7C3 and NbC) and finally a hypoeutectic structure (primary γ, γ+M7C3 and NbC). As the Nb content increases, the hardness and wear resistance of the coating first increase and then decrease, which is closely related to the NbC volume fraction first increasing and then the NbC size coarsening. The Fe-Cr-C coating with 11.65% Nb balances the NbC content and size, and has the highest hardness and best wear resistance. As the Nb content increases further, the formation and aggregation of coarse NbC carbides in the coating results in high brittleness of the coating, which may cause the carbide particles to peel off the coating during the wear process, thereby reducing wear resistance.

Effect of NbC on the microstructure, mechanical properties, and oxidation resistance of Ti(C,N)-based cermets

Abstract A comprehensive investigation of the effects of NbC on the microstructure and properties of Ti(C,N)-based cermets has been performed. Cermet samples were obtained via liquid-phase sintering under the guidance of thermodynamic calculations, and the amount of NbC was varied. The results showed that when the NbC content exceeded 12 wt.%, a hard phase with an NbC core appeared due to the lattice mismatch between the core and rim. NbC was not completely consumed by dissolution and precipitation, causing it to form a residual NbC core. As the NbC content increased, the grain size was refined, and the hardness of the cermet increased, but the fracture toughness decreased. When NbC was introduced into the cermet, a relatively dense protective layer was formed on the surface during oxidation, which restricted the diffusion of oxygen and improved the oxidation resistance of the cermet.

Microstructural evolution and wear behaviors of NbC-reinforced Ti-based composite coating

In situ ceramic phase reinforced Ti-based composite coatings were successfully fabricated on Ti-6Al-4V alloys by laser cladding using Ti + Al + Si mixed powders with different NbC contents (0, 5, 10, 15 wt.%). The effects of different NbC content on the microstructural evolution, hardness, and wear behaviors of the Ti-based composite coatings were studied. The results showed that the phase in the cladding layer was mainly consisted of Ti3Al, TiAl, and Ti5Si3 before NbC was added. After NbC was added, the TiC and Ti3AlC2 ceramic reinforcement phase was in suit synthesized. In addition, (Ti, Nb)C were also found. The in situ formed phases were proved beneficial to the improvement of the coating property. With the addition of NbC, the hardness of the coating is apparently increased. When the content of NbC is 15%, the maximum hardness of the coating is 1024 HV0.2, which is almost three times that of the substrate. The coefficient of friction of the coating without NbC was 0.591. With the addition of NbC, the coefficient of friction of S2, S3, and S4 was significantly decreased to 0.450, 0.388, and 0.375, respectively. Furthermore, the addition of NbC improves the worn surface of the coatings.

Evolution behavior of ex-situ NbC and properties of Fe-based laser clad coating

The NbC-reinforced Fe-based laser clad coatings were obtained by ex-situ processing. The evolution behavior of ex-situ NbC was quantitatively researched and the microhardness and wear resistance of laser clad coatings were also investigated. The results show that the ex-situ NbC added in clad powder can decompose and re-precipitate during the laser clad process, which affects significantly the content and morphology of NbC. After the added NbC particles decompose during the heating process of laser beam, Nb and C atoms are released into the molten pool. However, a part of Nb atoms cannot react with C to form NbC, but dissolve into the coating matrix or form Fe2Nb with Fe atoms, which decreases the content in NbC in clad coating. Moreover, Most of re-precipitated NbC phases belong to eutectic microstructure and exist in coatingin the form of network or featherlike structure instead of theoriginal particle shape. As heterogeneous nucleation core, the undecomposed NbC can promote the re-precipitation of new NbC phases. These new NbC can precipitate on the surface of undecomposed NbC particle, and then form the larger block and petaloid NbC phase with core. Both dissolved Nb atom and NbC precipitate can enhancethe microhardness and wear resistance of coating, but the promotion role on the wear resistance is more obvious.