WC Particles Research Articles

Effects of Electromagnetic Field on Microstructure and Properties of Ni‐ Based Coatings Reinforced by WC in‐Situ

The in situ WC‐reinforced Ni60 laser cladding layer‐assisted electromagnetic field is prepared on the H13 steel surface. The microstructure and phase of the cladding layer are analyzed by scanning electron microscope, energy disperse spectroscopy, and X‐ray diffractometry, the hardness and wear resistance of the coating are tested by microhardness tester and ring‐block friction and wear tester. The results indicate that more WC particles are generated with the increase in the magnetic field strength and current value, and many uniformly distributed eutectic carbides are formed in the coating, which makes the structure more uniform and dense. The average microhardness of the coating reaches 786.5HV when the electromagnetic intensity is 20 mT‐9 A, and the wear amount after 90 min is 35.2 mg, which is 65.7% of the nonelectromagnetic‐assisted WC/Ni60 coating and only 28.6% of the substrate, the wear resistance is obviously improved. The change in the structure and the improvement in microhardness and wear resistance are the result of the combined action of the directional Lorentz force generated by the electric field and the inductive Lorentz force generated by the magnetic field.

Influence of ultrasonic assistance on the microstructure and friction properties of laser cladded Ni60/WC composite coatings

The effects of different ultrasonic vibration powers on the distribution, phase structure, friction and wear properties of WC reinforced particles in laser melted Ni60/WC composite coatings are investigated. The effects of ultrasonic vibration on the microstructure, elemental distribution, crystal orientation, friction and wear properties of the fused coatings are analyzed. The experimental results show that the deposition of WC particles in the lower and middle parts of the coating is significantly improved after the introduction of ultrasonic vibration during the fusion cladding process. In particular, at 600 W ultrasonic power, not only the distribution uniformity of tungsten carbide particles in the coating is optimal, but also the composite coating shows better wear resistance. However, too much ultrasonic power increases the possibility of particle agglomeration. In addition, although the phase pattern of the coating does not change after ultrasonic vibration, the width of the columnar crystalline region of the coating is reduced, and the coating is covered by a homogeneous lamellar nanoscale eutectic structure with the phase compositions of the γ-(Fe, Ni) and M23C6 phases. The ultrasonic vibration improves elemental segregation of the coating, reduces the large number of precipitated phases in the coating, weakens the grain growth orientation, and relieves the local stress concentration in the coating. In addition, the mechanism of the influence of WC particles on the microstructure evolution and wear resistance of the composite coatings is discussed.

Solidification behavior of WC particles reinforced nickel alloy cladding layers by plasma surfacing: Simulation and experiment

In this work, a numerical simulation model was developed to investigate the complex heat and mass transfer process inside the molten pool during plasma surfacing. The temperature distribution and fluid flow were employed to depict the evolution of the molten pool. The findings revealed that the maximum temperature is located on the surface of the cladding layer corresponding to the position of heat source, and the temperature distribution follows a Gaussian distribution along the scanning direction. Thermal accumulation is obvious due to the continuous energy input in the initial stage, as a result, the maximum temperature and fluid flow velocity gradually increase with the deposition process. The maximum temperature and fluid flow velocity at 4.0 s are 1893 K and 0.281 m/s in case 110 A, respectively. The predicted shapes and dimensions are consistent with the results of the deposition experiments, with a maximum error of no more than 15 %. In order to investigate the impact of WC particles on the solidification microstructure of nickel composite layers, corresponding plasma surfacing experiment was implemented. The solidification characteristics of the microstructure follow planar-cellular-columnar-equiaxed crystals in the bonding layer and WC particles-columnar-equiaxed dendritic crystals in hard layer, respectively. Furthermore, the Ni dendritic near the retained WC particles transformed into columnar crystals due to temperature gradient in the local area.

The Effect of Solution Aging on the Microstructure and Mechanical Properties of a Laser Powder Bed Fusion-Formed WC-Reinforced 18Ni300 Composite

The addition of WC particles has the potential to improve the properties of 18Ni300 alloy, but the effect of heat treatment on the microstructure and mechanical properties of 18Ni300 matrix composites needs to be further investigated. In this work, WC-reinforced 18Ni300 composites were fabricated using laser powder bed fusion (LPBF). The composites were made into solutions at 846 °C for 51 min, followed by aging at 388 °C for 300 min. The microstructural evolution and compressive properties of the composites before and after heat treatment were systematically studied. The results indicate that the microstructures of the composites consist of heterogeneous cellular and fine columnar grains. As the WC content increases, the primary phase in the LPBF-formed samples gradually shifts from α-Fe martensite to γ-Fe austenite. After heat treatment, the primary phase transforms to α-Fe with only a small residual amount of γ-Fe. The microstructure becomes more uniform, featuring a significant reduction in grain size. Many precipitated phases can be found in the intergranular, accompanied by an increase in the thickness of diffusion layers. The WC content in the composite material is positively correlated with its hardness and compressive strength. As the WC reinforcement content increases from 5% to 20%, the yield strength and compressive strength of the LPBF-formed composites increase to 1042.5 MPa and 2900.7 MPa, respectively, while the compressive elongation decreases from 64% to 43%. After heat treatment, the yield strength of the composites significantly increases to 2356.8 MPa, with a slight increase in the compressive strength to 2939.7 MPa. However, the elongation decreases from 32.5% to 22%.

The effect of annealing on the microstructure and wear performance of laser-clad high-entropy alloy composite coatings for monorail crane braking systems

Laser cladding was utilized to fabricate WC ceramic particle-reinforced CoCrFeMnNi high-entropy alloy (HEA) composite coatings, with an investigation into the influence of annealing heat treatment on the microstructure and wear behavior of the composite coatings. The HEA composite coatings with a WC particle content of 30 wt% primarily consist of a face-centered cubic (FCC) solid solution phase, various M6C carbides with blocky, fishbone, and dendritic morphologies, and incompletely melted WC ceramic particles. The microstructure of the composite coatings remains stable up to a temperature of 570°C. After annealing at 600°C, the microstructure transforms into a typical dendritic morphology with rod-like carbides precipitating from the solid solution and discontinuously distributed in the interdendritic regions. Due to the annealing softening effect, the microhardness of the coating decreases from 488.1 HV0.3 to 443.1 HV0.3. Following annealing at a high temperature of 800°C, recrystallization leads to a refined equiaxed grain microstructure, with precipitated carbides continuously distributed along the grain boundaries, forming a network. The combined effects of precipitation hardening and fine grain strengthening result in an increase in the microhardness of the coating to 568.6 HV0.3 after annealing at 800°C. As the annealing temperature increases, the wear rate of the WC particle-reinforced CoCrFeMnNi HEA composite coatings also increase. The wear mechanism for the unannealed coating is oxidative wear, and the reduction in hardness leads to adhesive phenomena in the coating after annealing at 600°C. The network of carbides reduces the ductility of the HEA and also the toughness of the oxide film, resulting in the highest wear rate for the coating annealed at 800°C, reaching 38.636×10−6 mm3/(N·m). This study provides valuable insights for the fabrication of advanced wear-resistant coatings.

Effect of powders recycling on microstructure evolution and wear mechanism of plasma sprayed Ni625-WC composite coating

The utilization rate of metal powders during the preparation of plasma-sprayed coatings is typically below 70 %, which has raised significant concerns regarding efficiency. The microstructure evolution and wear mechanism of plasma-sprayed Ni625-WC composite coatings with received powders (C-p1) and recovered powders (C-p2) were studied to investigate the feasibility of powder recycling. The results showed that the boundary layer at WC particles in C-p2 was 2.84 μm thicker than that in C-p1. Decarburized WC products were dispersed nucleation to form block M23C6 at the boundary of WC particles and within Inconel 625 matrix in C-p1. In contrast, the larger contact area of block M23C6 after initial heating promoted the nucleation and growth of acicular M23C6 in C-p2. In addition, the wear rate of C-p2 is 9.1 % lower than that of C-p1. Although the higher elastic modulus (E) of C-p1 caused the Inconel 625 matrix to adhere more strongly to WC particles, resulting in higher degree adhesive wear rather than exfoliations and less adhesion in C-p2, the presence of harder and more uniformly distributed acicular M23C6, and higher microhardness (H)/E ratio in C-p2, improved the wear resistance.

Preparation and formation mechanism of (W) WC/Fe bundle reinforced iron matrix composites

To address the issue of strength and toughness inversion in traditional metal matrix composites, which are reinforced by uniformly distributed ceramic particles, this research developed a novel space bundle configuration of reinforced iron matrix composite using tungsten wire (W) and tungsten carbide (WC). This composite was prepared using a lost foam casting process combined with in-situ reaction. Microstructural analysis revealed that WC particles are distributed along the tungsten wire, with larger particles at the center and smaller ones at the edges. The formation of the reinforcement occurs in two stages: first, a solid-liquid reaction between the solid tungsten wire and molten iron during the lost foam casting process, promoting WC formation at high temperatures and carbon potential; second, an in situ solid-solid reaction where Fe diffuses and Fe3W3C decomposes, forming a composite structure of WC and α-Fe. The composite obtained at 1100°C for 9 hours exhibited a compressive strength of 836.59 MPa and a fracture strain of 18.69%, representing increases of 48.46% and 48.69% respectively compared to grey cast iron (GCI). The (W) WC/Fe bundle reinforcement effectively enhances the strength and toughness of the composite through the high volume fraction and gradient distribution of WC particles, combined with the synergistic effect of α-Fe. This research provides a new strategy for improving the mechanical properties of composite materials and resolving the issue of strength-toughness inversion.

Microstructure and wear behavior of WC-reinforced AlCoCrFeNiSi high entropy alloy coatings prepared by high-velocity arc spraying

In this study, AlCoCrFeNiSi/WC (WC from 0 to 40 wt%) high entropy alloys (HEAs) coatings were deposited on Q235 steel substrates using high-velocity arc spraying technique. The coatings' phases, microstructure, microhardness, nano-hardness, wear properties, and the mechanisms of wear were examined. The results have shown that the WC reinforced HEA had faced-centered cubic, body-centered cubic solid solution and carbide phases, while faced-centered cubic solution and Cr3Si, Al2O3 phase were observed in AlCoCrFeNiSi coating. The coatings possess a dense, lamellar structure and strong adhesion to the substrates. With the addition of reinforced particles, the porosity of the coatings initially decreases and then increases. The average microhardness of the coatings is significantly improved as WC content increased, reaching a maximum of 530 HV0.1. The ratio of nano-hardness to reduced elastic modulus rises as more WC is introduced. The coatings with the WC particles exhibit good wear resistance with the optimum wear rate at WC content of 40 wt%. Under the same conditions, the coating with 40 wt% of WC displayed the lowest wear rate, which decreased by 60.5 % compared to the AlCoCrFeNiSi coating. The AlCoCrFeNiSi coating experienced a mix of adhesive, abrasive, oxidative, and fatigue wear mechanisms. The wear mechanism changed to more abrasive, adhesive, and oxidative in the reinforced coatings. The load-bearing capacity and secondary phase strengthening effects of WC reduce the wear rate of the coatings.

Bonding behavior of Ti-6Al-3Nb-2Zr-1Mo/WC composite coating on titanium alloy by gas tungsten arc welding cladding

In this study, tungsten carbide (WC) ceramic particles were introduced into the molten pool of gas tungsten arc welding (GTAW) to successfully prepare a composite coating without solidification cracking and with lower dilution. The formation mechanism and properties of the bonding interface are deeply analyzed. Results demonstrate that metallurgical bonding was achieved. The dissolution behavior of WC particles and the diffusion of W element into the heat-affected zone promoted the formation of a special β(Ti, W) diffusion layer below the fusion line. (Nb, Ti)C was mainly found distributed close to the diffusion layer. Nanoindentation test results show remarkable inhomogeneity in the interface area. The fracture surface of the broken coating revealed that the titanium matrix exhibited quasi-cleavage fracture, while the particles displayed brittle fractures. The fracture surface of coatings that experienced decohesive rupture in the shear test underwent plastic deformation in the shear direction.

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 WC particle size on the microstructural evolution and tribological properties of laser cladding Ti-bearing Co-based WC reinforced coating

To improve the wear resistance of 300 M steel under reciprocating wear in landing gear shock strut, Ti-bearing Co-based WC reinforced coatings with three different WC particle sizes (280 mesh, 200 mesh, and 150–300 mesh) were successfully fabricated by laser cladding method. The effect of WC particle size on phase composition, microstructure, microhardness and tribological properties were systematically investigated. The results show that the phase composition of these coatings consists mainly of γ-Co, TiC, WC, Cr23C6 and CrCo, and that varying the WC particle size changes the morphologies of the second phases. With the increase of WC particle size, the morphology of TiC is dendritic, ellipsoidal and block, respectively; the morphology of Cr23C6 changes from discontinuous fine particles to grid-like at grain boundaries. And the TiC-WC composite phases appear when the particle size of the added WC particles is a mixture. The coating with a mixture of 150–300 mesh WC particles, has the highest hardness range, the lowest average friction coefficient of 0.372, and the lowest wear rate of 9.61 × 10−5 mm3/N·m. The wear mechanisms of all three coatings are abrasive wear and oxidation wear, and the oxide film on the worn surface of the coatings gradually becomes denser and more continuous with increasing WC particle size.

Elevated Temperature Tribological Behavior of Duplex Layer CrN/DLC and Nano Multilayer DLC-W Coatings Deposited on Carburized and Hardened 16MnCr5 Steel

This study investigates the impact of temperature on the tribological performance of duplex layer CrN/DLC and nano-multilayers DLC-W coatings deposited using hybrid PVD-PECVD techniques on carburized and hardened 16MnCr5 discs cut from internal combustion engines valve tappets. Reciprocating dry sliding experiments were conducted at 25 °C, 150 °C, 200 °C, and 250 °C to analyze the high-temperature tribological behavior of the coatings. The wear mechanisms were characterized using SEM, EDS mapping, Raman spectroscopy, and nanoindentation. The lowest coefficient of friction was obtained for CrN/DLC at 25 °C. The CrN/DLC coefficients of friction (COF) increase with temperatures due to increasing adhesive wear. Similarly, DLC-W exhibited a comparable trend with increasing temperature from 25 °C to 250 °C. Both coatings’ wear resistance decreased with higher temperatures due to the transformation of sp3 C bonds to sp2 C bonds, facilitating the plastic deformation of the coatings and afterward of the substrate. The CrN/DLC displayed superior wear resistance to the DLC-W coating across all temperatures. The DLC-W multilayer coating showed poor wear resistance above 150 °C, being completely removed during the testing. Compared to both coatings, the uncoated 16MnCr5 discs exhibited higher coefficients of friction and wear rates at all temperatures. Predominant wear mechanisms observed in the coated discs were adhesive and abrasive. The study revealed a decrease in the coatings’ structural and mechanical properties with rising temperatures. Hard abrasive WC particles were identified as contributing to increased wear rates in the multilayer DLC-W coatings.

Simulation of Localized Stress Impact on Solidification Pattern during Plasma Cladding of WC Particles in Nickel-Based Alloys by Phase-Field Method

As materials science continues to advance, the correlation between microstructure and macroscopic properties has garnered growing interest for optimizing and predicting material performance under various operating conditions. The phase-field method has emerged as a crucial tool for investigating the interplay between microstructural characteristics and internal material properties. In this study, we propose a phase-field approach to couple two-phase growth with stress–strain elastic energy at the mesoscale, enabling the simulation of local stress effects on the solidified structure during the plasma cladding of WC particles and nickel-based alloys. This model offers a more precise prediction of microstructural evolution influenced by stress. Initially, the phase field of WC-Ni binary alloys was modeled, followed by simulations of actual local stress conditions and their impacts on WC particles and nickel-based alloys with ProCAST and finite element analysis software. The results indicate that increased stress reduces grain boundary migration, decelerates WC particle dissolution and diffusion, and diminishes the formation of reaction layers and Ostwald ripening. Furthermore, experimental validation corroborated that the model’s predictions were consistent with the observed microstructural evolution of WC particles and nickel-based alloy composites.

Effect of WC addition on microstructure and properties of laser melting deposited Ti6Al4V

Titanium alloys are generally characterized by low surface hardness, poor thermal conductivity, high friction coefficients and susceptibility to adhesive wear, which significantly hinder their industrial applications. To address this issue, we enhance the wear resistance of titanium alloys by incorporating nano WC particles. However, the optimal amount of WC to be added to titanium alloys remains unexplored. In this study, we prepared Ti6Al4V-xWC (wt%) (x = 0, 10, 20) coatings on Ti6Al4V substrates using laser melting deposition, specifically examining the effects of WC content on the microstructure and properties of the coating. The experimental findings indicate that the introduction of WC particles resulted in the formation of a TiC reinforced phase within the composite coating which promoted the equiaxialization of lamellae α phase. The hardness of the coatings increased significantly with the increase of the mass fraction of WC nanoparticles. Notably, the Ti6Al4V-10WC and Ti6Al4V-20WC coatings exhibited wear resistance that was 2.5 and 3.4 times greater, respectively, compared to the Ti6Al4V coatings. This enhancement in wear resistance can be attributed to the reinforcing phase (TiC) formed by the addition of WC. This experiment demonstrates a viable approach to improving the wear resistance of the Ti6Al4V titanium alloy through surface treatment.

A comparative investigation on the effects of reinforcement phase addition methods on laser melting deposited WC/Co coatings

To unravel the fundamental mechanisms underlying the influence of ceramic phase addition methods on the formation quality and performance enhancement of coatings, the WC/Co-based composite coatings were manufactured on 42CrMo substrate utilizing laser melting deposition technology with different reinforcement phase addition methods grounded in the variable-process alternated overlapping strategy. A comparative analysis was conducted to examine the phase transformations, surface fluctuations, pore defects, microhardness, wear resistance and corrosion behavior. The findings revealed that the in-situ formation of tungsten-carbide phase fell short of the anticipated level due to the physical properties and size constraints of W particles. Notably, the 40 wt% WC particles addition significantly hindered the molten pool fluidity and impeded gas release, leading to pronounced a surface fluctuation of 180.14 μm and a porosity of 31.06 %. In contrast, the direct addition WC particles imparted support, pinning, and strengthening effects, resulting in the optimal microhardness and wear resistance compared to other addition methods, which are 1.46 times and 3.75 times higher than the 42CrMo substrate, respectively. However, an increase in WC particles destabilized the passivation film and promoted the formation of corrosion channels, ultimately exacerbating the corrosion behavior of the WC/Co-based coatings. These insights provide vital theoretical guidance and technical foundations for the adaptive selection of ceramic phase addition methods tailored to the actual working conditions and desired strengthening effects of reinforced coatings for key components.

Effect of Laser Power on Microstructure and Properties of WC-12Co Composite Coatings Deposited by Laser-Based Directed Energy Deposition.

During the laser-based directed energy deposition (DED-LB) processing, a WC-12Co composite coating with high hardness and strong wear resistance was successfully prepared on a 316L stainless steel substrate by adopting a high-precision coaxial powder feeding system using a spherical WC-12Co composite powder, which showed a large number of dendritic carbides and herringbone planar crystals on the substrate-binding interface. The influences of laser power on microstructural and mechanical properties (e.g., hardness, friction resistance) of WC-12Co composite surfaces were investigated. The results show that laser power has a significant effect on determining the degree of Co phase melting around the WC particles and the adhesion strength between the matrix and the coating. Lower laser power does not meet the melting requirements of WC particles, thus weakening the molding quality of the composite coating. At high laser power, it is possible to dissolve the WC particles and melt the metal powder between the particles, thus improving the material properties. The laser power increased from 700 W to 1000 W and the average hardness of the coating surface gradually increased from 1166.33 HV to 1395.70 HV, which is about 4-5 times higher than the average hardness of the substrate (about 281.76 HV). In addition, the coatings deposited at 1000 W showed better wear resistance. This work shows that the processing parameters during laser-directed energy deposition can be optimized to prepare WC-12Co composite coatings with excellent mechanical properties.

The Microstructure and Properties of Ni60/60% WC Wear-Resistant Coatings Prepared by Laser-Directed Energy Deposition.

Ni60/60% WC composite coatings with a good surface roughness and high mechanical properties were successfully prepared on 316L stainless steel substrate by laser-directed energy deposition (LDED) technology. The effects of laser power on the microstructural evolution and mechanical properties of the Ni60/60% WC composite coating were investigated. The relationships between the chemical composition, the microstructure, the hardness, and the friction wear resistance of the composite coatings were characterized and investigated. The results show that the laser power had a significant effect on the energy input, which determined the melting extent of the Ni60 phases around the WC particles and the bonding strength between the reinforcements and the matrix, as well as the bonding strength between the substrate and the coatings. With an increase in the laser power from 800 W to 1400 W, the average hardness of the coating surface increased due to the increased densification of the deposited coatings and then decreased due to grain coarsening under a high energy input. The average coefficient of friction of the coatings decreased gradually to 0.383 at 1000 W, showing a minimum wear of 0.00013 mm2 at 1200 W. The main wear mechanisms on the coated surfaces were adhesive wear and abrasive wear. Moreover, the coatings deposited at 1200 W exhibited better forming quality and wear resistance. This work suggests that the processing parameters during LDED can be optimized to prepare Ni60/60% WC wear-resistant coatings with excellent mechanical properties.

Microstructure characterization and high-temperature wear mechanism of high-entropy alloy matrix composite coating fabricated by laser cladding

The development of diecasting technology requires hot die steels with high-temperature resistance. In this study, a high-entropy alloy (HEA) was combined with ceramic particles to generate a CoCrFeNiMo0.2Nb0.2/WC composite coating via laser cladding. The coating consisted of a face-centered cubic (FCC) matrix with unmelted WC particles, eutectics and nanoscale (Mo)NbC phases. With the strong lattice distortion caused by the sequestration of W atoms, a nanoscale amorphous layer existed between the Laves and HEA matrix phases. A transition layer with the same structure as the Laves phase was facilitated between the WC particles and the HEA matrix. Due to the hard phases in the HEA matrix and their interfaces, the composite coating with a high proportion of WC exhibited excellent wear resistance under high-temperature dry friction conditions. When the WC was 60 wt%, a minimum wear rate reached to 0.74 × 10−5 mm3/(N·m) at 600 ℃ and 1.46 × 10−5 mm3/(N·m) at 800 ℃. The destruction pattern of the composite coating at 600 ∼ 800 °C was due to the interaction of the adhesive, oxidative and abrasive wear. The composite coatings fabricated in this study provide a route to enhance the high-temperature wear resistance of die-casting molds.

Microstructure and Mechanical Properties Evolution of W@WC/Fe Core–Shell Bar‐Reinforced Iron Matrix Composites: Effect of In‐situ Solid Diffusion Time

To improve the strength and toughness of conventional particle‐reinforced iron matrix composites, W@WC/Fe core–shell bar‐reinforced iron matrix composites (CBIMCs) are synthesized by casting and in‐situ solid‐phase diffusion method. These composites, which have an architecture similar to concrete, consist of a core of residual W bar and a shell of gradient‐structured WC‐Fe layer. The effect of in‐situ solid diffusion time on the evolution of microstructure and mechanical properties of the composites is investigated. It is observed that for in‐situ solid diffusion times ranging from 3 to 24 h, the reinforcement in the composites remained as W@WC/Fe core–shell bars. As the solid diffusion time increased, the diameter of the W core gradually decreased, and the thickness of the WC‐Fe shell layer increased. At a solid diffusion time of 30 h, the reinforcement transitioned to the WC‐Fe composite bar. Additionally, with longer solid diffusion times, the WC particles transformed from a triangular prism shape to a truncated octahedron. The composite prepared at 18 h exhibits the highest ultimate compression strength and strain, reaching values of 1100 ± 18 MPa and 35.5 ± 1.3%, respectively. This excellent ultimate compression strength is mainly due to the WC particles, which enhanced load transfer strengthening and dislocation strengthening. Moreover, the metal W core and iron matrix effectively hinder microcrack propagation, thus contributing to the enhanced toughness of the composite.

A new test for evaluating the cracking susceptibility of laser cladding coatings and its validity on assessing the effect of laser power

Cracking is one of the most common and destructive defects and Ni-based superalloys are susceptible to hot cracking during laser cladding. In this study, a new test was developed to evaluate the cracking susceptibility of materials during laser cladding, and the crack rate was used as an evaluation criterion for cracking susceptibility. Three groups of different laser powers (1.2 kW, 1.5 kW, and 1.8 kW) were selected to assess the validity of test in terms of effect of laser power on the cracking susceptibility. The cracking rates of coatings were 15.5 %, 20.4 %, and 22.0 %, respectively. It was observed that the cracking rate increased with increasing laser power, as the crack depth also increased due to the effect of the laser power on the substrate with a processed gap. The reinforcements, which were partially melted WC particles and in-situ generated reinforcements, had a similar impact on crack propagation. If there were no microcracks within the reinforcement, the crack bypassed the reinforcement and continued to propagate along the interface between the reinforcement and the matrix. When microcracks were present within the reinforcement, the stress concentration caused the crack to propagate through the microcracks within the reinforcement, crossing the reinforcement and propagating forward. Additionally, a special cored-eutectic microstructure, consisting of inner ceramic particles and fine lamellar eutectics, was found in coatings created using 1.2 kW.