Hard Particles Research Articles

Research on polishing aluminum alloy optical elements with a new solid flexible bonnet tool

As a common optical element material, aluminum alloy has been widely used because of its high reflectivity, easy lightweight design and other advantages. However, due to the soft texture and large plasticity of aluminum alloy, the surface is prone to mechanical damage during processing. In order to improve the surface quality and processing efficiency, this paper designs a new type of solid flexible bonnet tool to polish aluminum alloy optical elements. Then the finite element analysis method is used to compare the performance of several bonnet tools. Finally, the aluminum alloy polishing experiment is carried out, and the material removal mechanism and the factors affecting the polishing surface quality are analysed. The results show that the new solid flexible bonnet tool has good deformation stability, good fit with the workpiece, and can achieve high efficiency and precision polishing of aluminum alloy optical elements. According to the pressure distribution in the contact area, the abrasive particles in the sliding state are divided into three removal modes: micro-cutting, micro-plowing and micro-rubbing. At the same time, the hard particles in aluminum alloy have an important influence on the surface morphology after polishing. Due to the strong plasticity and viscosity of aluminum alloy, the abrasive dust is easy to adhere to the surface of the workpiece, reducing the surface roughness.

Particle Behavior and Aperture Optimization of Variable Vibration-Amplitude Screening Based on Discrete Element Method Simulation.

Recently, some novel screens were proposed based on the improved understanding of screening processes from particle-scale studies, one of which is the novel variable amplitude equal thickness vibration screen (VAETVS). This paper presents an investigation of using different aperture sizes to further optimize the VAETVS by the discrete element method (DEM). The screen was divided into three panels, and the aperture size of each panel was varied in the simulation. The particles' dynamics and spatial distribution were investigated to better understand the effects of varied amplitudes and aperture sizes on the screening efficiency. The results showed that the VAETVS can be effectively optimized by varied amplitude as well as varied aperture size for different screen panels. The amplitude variance is more effective for hard sieve particles and hindrance particles. It is also found that from the feed end to the discharge end, the difference in the distribution of particle mass between the coarse particles and the fine particles increases. Generally, such a difference can be increased with increasing aperture sizes. However, the effects of the apertures of the different panels were not the same. The simulated data were further analyzed by the Box-Behnken response surface method, which gave a mathematical model to predict the screening efficiency η with the varied apertures. From the model, the optimal aperture sizes are 7.5, 7.58, and 6.81 mm, yielding the maximum screening efficiency of 86.35%, and the optimal opening areas for the three panels are 35, 40, and 40%, respectively, yielding the maximum screening efficiency of 87.82%.

Laser shock dynamic compaction of aluminum–copper (Al–Cu) composite metal powder

Laser impact dynamic compaction experiments and 2D multi-particle finite element method (MPFEM) simulations were carried out on aluminum–copper (Al–Cu) binary-based composite powders. Al–Cu compacts with densities of about 95% were successfully prepared at the maximum laser energy of 1.8 J. Research trends indicate that higher power lasers could nearly achieve the theoretical densities. Analysis of the influence laws of laser energy and copper powder mass fraction on the densities of Al–Cu compacts was carried out, and the effects of microstructure and microhardness of Al–Cu compacts on their mechanical properties were investigated, as well as the stresses and velocities in the dynamic compaction process of Al–Cu composite powders were analyzed. The results showed that the relative densities of composite powder compacts of Al-5 wt%Cu gradually exceeded those of Al-10 wt%Cu and Al-15 wt%Cu with the increase of laser energy. In laser impact dynamic compaction the mechanism of inter-particle joining was solid-state press-welding, and the increase in the hardness of the Al–Cu compacts could be attributed to the inherent hardness of the hard particles. The upper particles have a localized maximum velocity of more than 300 m/s, which met the explosion welding velocity, thus localized cold welding occurred and contributed to the inter-particle connection.

Effect of nano∖micro‐textures on the enhancement of tool wear resistance in green ceramics processing

AbstractThe processing of green ceramics aims to obtain parts with complex shapes and good surface quality. This paper prepared tools with micro/nano‐textured flank face by femtosecond laser to improve the cutting performance in processing of Al2O3 green ceramics. The wear resistance of cutting tools and characteristics of machined compacts are analyzed. Results shows that textures can improve the wear resistance of cutting tools and surface quality of green ceramics. Micro/nano‐textured tools own the best cutting performance, the improvement rate of wear resistance and surface roughness can reach 28.5% and 25% respectively. The reasonable mechanisms are explained by the storage of powder chips and the derivative‐cutting phenomenon by textures. The derivative‐cutting behavior can prevent cutting tool from severe abrasive wear by hard phase particles. The storage function prevents the powder chips from scratching the unworn surface of cutting tools, and the additional scratching of the machined surface by the hard phase particles is reduced. The two functions contribute to the improvement of cutting performance of micro/nano‐textured tools.

Effect of the Reinforcing Particle Introduction Method on the Tribomechanical Properties of Sintered Al-Sn-Fe Alloys

The present paper reports the results of the comparative study of mechanical properties of sintered disperse-strengthened Al–40Sn alloy depending on the method of reinforcing particle introduction. The study is performed on two mixtures of aluminum and tin powders: one is admixed with 5.5–14.6 wt% of pure iron powder and the other contains the same amount of iron, but as a component of aluminide Al3Fe powders. The volume fraction of tin remains unchanged in all mixtures, being equal to 20%, and the concentration of hard particles increases due to a decrease in the volume fraction of the aluminum phase. Green compacts are sintered in the vacuum furnace at a temperature above the melting point of aluminum. The sintered material is a composite containing three phases: α-Al, β-Sn, and Al3Fe, in which the tin volume fraction is constant. Testing of the sintered composites for compression shows that the addition of finished Al3Fe particles has a more beneficial effect on their mechanical properties as compared to the addition of pure iron powders. In the latter case, aluminides are formed during sintering. The ultimate strength of composites reaches 180 MPa. Mechanisms of sintering of composites and the related structure and mechanical properties are discussed.

Sliding frictional characteristic of tight sandstone and its influence on the hydraulic fracture complexity

The complexity of the fracture network during hydraulic fracturing is closely related to the frictional characteristics of the reservoir rock, which largely depends on the rock’s mineralogical properties and the type of fracturing fluid. In this study, the micro-friction characteristics of three kinds of tight sandstone were tested using an indoor rock micro-friction setup. The effects of different hydraulic fluids and rock mineralogical properties on the friction coefficient were investigated. A numerical model was then developed to investigate the influence of different friction coefficients on fracture propagation. The results indicate that the friction coefficients of tight sandstones are closely related to their content of clay and quartz. When the content of clay is low (around 20%), the content of hard particles such as quartz and feldspar is high, the friction coefficient of the rock appears to be high and insensitive to the wetting characteristics of the fracturing fluid. Conversely, when the clay content is high (around 30%), rock friction coefficients tend to be sensitive to different types of fracture liquids, and decrease when the liquid wets the rock. The numerical simulation results indicate that a 0.4 friction coefficient produces the maximum of fracture complexity. These findings provide a potential method on how to increase the productivity of unconventional plays by generating complex fracture networks.

Dramatic improvement of the strength of laser welded joints of Nb521 to GH3128 by adding pure copper as an interlayer

Weld cracks and low weld strength of Nb521 to GH3128 dissimilar metal welded joint are key factors influencing their weldability. To obtain favorable crack-free laser welded joints, this research adopted copper as an interlayer to research the microstructure and properties of laser direct welded and laser offset welded joints of Nb521 to GH3128 superalloy. Compared to previous research results, the tensile strength of laser direct welded joints is enhanced by 2.5 folds. There is a melting reaction layer at the position where the center welded joints are adjacent to the Nb521 base metal, and Ni3Nb and Laves phases are present in the layer. The copper solid solution is located in the center of fusion zone, and Ni3Nb-Laves hard particles are found. The phases near the side of GH3128 superalloy base metal are Ni solid solution, Cu solid solution, Ni3Nb/Cr2Nb hard particles and high melting point alloy mixture. Macrosegregation at the laser offset welding fusion zone is more serious. The phases near the Nb521 base metal are Nb solid solution, Cu solid solution, Ni3Nb and Cu/Cr eutectic structure. At the center of the fusion zone, Cu solid solution, Ni3Nb and Cu/Cr eutectic structure are observed. The phases near GH3128 base metal are Ni solid solution, Cr2Nb phase and Cu solid solution. Mean Vickers hardness values of the direct welded fusion zone is 271.7 ± 129.8 HV, which reduces mismatching of hardness of the joints to a certain degree. As there are Laves phase and Ni3Nb brittle phase in the melting reaction layer adjacent to Nb521 base metal, the microhardness value is up to 589.1 HV. The average microhardness of the offset welded fusion zone is 449.1 ± 217.4 HV, which is higher than the hardness of Nb521 and GH3128 base metals, due to increasing number of brittle phases in the joints. Strength values of the direct welded and offset welded joints are 418.7 ± 49.8 MPa and 364.3 ± 24.5 MPa respectively, which are separately 86.0% and 74.8% of Nb521 base metal. Fractures are all found to occur at the fusion zone on the side of Nb521. The direct welded joints exhibit mixed fracture characteristics with dimples and cleavage facets on the fracture, while the offset welded joints are characterized by brittle fracture.

Laser cladding of electroplated Ni-WC on surface of TA2：microstructure and mechanical properties

The combination of electroplating Ni/WC composite coating and laser cladding was utilized to modify surface of TA2 substrate. Microstructure of the Ni/WC composite coating was characterized by SEM and TEM. The composite coating consists mostly of TiNi-WC layer and Ti2Ni layer. The phases in the TiNi-WC layer include TiNi, unreacted Ti and uniformly dispersed WC, while Ti2Ni is the main phase in the Ti2Ni layer. The composite coating shows remarkable nano-hardness (9.5 GPa) compared to the TA2 substrate (2.5 GPa), which is contributed by residual WC particles in the laser remelted coatings. In addition, the hard phase WC particles facilitates the wear resistance of the laser remelted Ni/WC coating. Abrasive wear and adhesive wear mechanism are dominant in the friction and wear mechanism.

Numerical simulation of liquid–solid two-phase flow and erosion of Y-type slurry valve with different openings

Most conveyed industrial slurries contain hard particles, and the Y-type slurry valve is eroded after the long-term operation, causing economic losses. In this study, the liquid–solid two-phase flow and erosion characteristics of the Y-type slurry valve were studied. The distribution positions of particles with different sizes were determined, and large particles showed a deposition phenomenon. The particle distributions were more dispersed. At smaller valve opening degrees and the average velocity of solid particles decreased with the increase in valve opening degree. The main erosion area of the valve was concentrated on the ring area around the valve body connecting the downstream pipeline, and the valve disc. The relationship between the particle size and the erosion rate was analyzed, and the distribution of the main erosion area was obtained.

Analytical modeling of a magnetoactive elastomer unimorph

Magnetoactive elastomers (MAEs) are capable of large deformation, shape programming, and moderately large actuation forces when driven by an external magnetic field. These capabilities enable applications such as soft grippers, biomedical devices, and actuators. To facilitate complex shape deformation and enhanced range of motion, a unimorph can be designed with varying geometries, behave spatially varying multi-material properties, and be actuated with a non-uniform external magnetic field. To predict actuation performance under these complex conditions, an analytical model of a segmented MAE unimorph is developed based on beam theory with large deformation. The effect of the spatially-varying magnetic field is approximated using a segment-wise effective torque. The model accommodates spatially varying concentrations of magnetic particles and differentiates between the actuation mechanisms of hard and soft magnetic particles by accommodating different assumptions concerning the magnitude and direction of induced magnetization under a magnetic field. To validate the accuracy of the model predictions, four case studies are considered with various magnetic particles and matrix materials. Actuation performance is measured experimentally to validate the model for the case studies. The results show good agreement between experimental measurements and model predictions. A further parametric study is conducted to investigate the effects of the magnetic properties of particles and external magnetic fields on the free deflection. In addition, complex shape programming of the unimorph actuator is demonstrated by locally altering the geometric and material properties.

Analysis of wear mechanism and sawing performance of carbide and PCD circular saw blades in machining hard aluminum alloy

High-efficiency sawing is widely applied in primary and secondary machining sectors, but it faces limitations due to saw tooth life and manufacturing constraints. This research investigates the wear mechanism, wear characteristics, and sawing performance of carbide and polycrystalline diamond (PCD) saw teeth when machining hard aluminum alloy. The results show that the sawing forces with PCD saw teeth are less than those of carbide teeth, yielding better surface quality and longer tool life. The wear mechanisms of saw teeth of two materials with different tooth types are classified and characterized finely. Carbide teeth are subject mainly to abrasion and adhesion at the cutting edges, while adhesion, corrosion, and diffusion primarily contribute to flank face wear. PCD teeth mainly suffer from abrasion and micro-chipping on the cutting edges and faces. A comprehensive description of the wear evolution of carbide and PCD teeth is presented, with the cutting heat being the primary cause of carbide tooth wear and the presence of hard particles in the workpiece causing PCD tooth wear by SEM and EDS analysis. The friction coefficient of the PCD teeth is considerably lower than that of the carbide teeth by sliding friction and wear tests, which also proves its more superior thermal stability and wear resistance during wear evolution analysis. Systematic research analyzes and discusses the wear mechanism and wear characteristics of saw teeth in high-speed sawing process, which can further enhance the understanding of the saw tooth wear to provide theoretical guidance for saw tooth design and manufacturing.

Effect of binder phases on the cavitation erosion behavior of HVOF sprayed WC-based coatings

In order to address the issue of cavitation erosion (CE) damage in marine mechanical components, WC-10Co4Cr (WCC), WC-10Co (WC1) and WC-17Co (WC2) coatings were prepared on the surface of 316L stainless steel using high-velocity oxygen-fuel (HVOF) spraying technique. The study investigated the microstructures, phases, mechanical properties and CE behavior of the coatings with different binder phases. The effects of the type and content of binder phase on the CE resistance and mechanism of the coatings were studied by compared the differences of volume loss rate (VLR) and eroded surface morphologies between the coatings. It was observed that all three coatings were dense and tightly bonded to the substrate. The primary phases identified in the coatings were WC, W2C and Co3W3C. Compared with the WC1 and WC2 coatings, the WCC coating demonstrated superior CE resistance with the lowest volume loss rate (VLR). The VLR of the WC1 and WC2 coatings was approximately four times higher than that of the WCC coating. The binder phase of Co-Cr improved the mechanical properties and the bonding strength of hard and binder phase, which reduces the brittle detachment of WC particles. In addition, the WCC coating had high microhardness and elastic modulus (E), H/E and H3/E2, which hindered the initiation and propagation of fatigue cracks. The initiation of CE damage occurred at the original defects, such as pores, cracks. The primary CE mechanism of the coatings was the interlinking of cavitation craters, lamellar spalling caused by the fatigue cracks propagation along the interlayer. The brittle detachment of WC hard particles also occurred significantly in WC1 and WC2 coatings due to loss of the binder phase. It was concluded that the binder phase markedly influenced the CE resistance and mechanism of the coatings, the addition of Cr showed the most pronounced effect.

Significant hardening effect of high-temperature aging of alloy Ti-6Al-4V composite reinforced with TiC

Titanium alloy composites, reinforced with a light second phase and made using inexpensive powder metallurgy, attract considerable attention due to the directness of their intentional hardness increase without compromising low weight of materials. In this study the metal-matrix composites (MMC) of Ti-6Al-4V alloy reinforced with light and hard particles of TiC (up to 80%, vol.) were made using blended elemental powder metallurgy of hydrogenated titanium. Post-sintering solution treatment for 45 min. at 880 °C and 1000 °C and water quenching followed by the 5 hrs. aging at 550 °C was used to additionally refine the microstructure and properties of MMC. For the duration of thermal exposure throughout solution treatment and additional aging the matrix and reinforcement phase underwent distinct structural changes that modified the mechanical properties of materials. It has been shown that the used reinforcement presents an exceptional opportunity for hardening of Ti-based composites without compromising their low specific weigh. It can increase the hardness of material by more than 40% due to the ability of TiC to chemically react with the matrix to form a strong interfacial bond and its ability to form hard compounds of Ti2C and Ti3AlC in the expense of the relatively soft matrix alloy.

Improvement Mechanical Properties of Epoxy Composite Reinforced with Sisal, Ramie and Carbon Fibers

In this paper, justification of mechanical characteristics is carried out to determine the ability of bio-composites to become structural composite bicycle frames capable of achieving strengths of more than 300 [MPa]. Sisal fiber is a natural fiber that is widely used as a composite fiber and is easy to cultivate. The fiber is believed to originate from Central and South America. Nearly 4.5 million tons of sisal fiber are produced annually worldwide, according to FAO. In building structural materials, in addition to structural strength, it is hoped that the material will also have good ductility. For this reason, the assembled bio-composite material consists of carbon fiber, ramie fiber, sisal fiber. The fiber is then mixed with hard epoxy resin, soft epoxy and aluminum particles 9 µm which are mixed until smooth and even. The significant increase in material strength is obtained from the strength of carbon fiber. Another thing is that the ductility of the material is obtained due to sisal and ramie which are bound by a mixture of epoxy resins. Because the quality of plant products is very dependent on the agricultural process, this study, the residual material was taken from the Subang (Indonesie) area and the ramie fiber was obtained from the Bandung market. Because agricultural cultivation in Indonesia still emphasizes the use of chemicals, basically this also has an impact on plant bio elements. However, research using local materials was still able to obtain strength reaching ~480 MPa, so it is still good. In this research, the tensile test was carried out 3 times so that it is known that the fiber taken from a rope has the greatest tensile strength which reaches around 480 MPa.

The effect of the diode laser beam power on the behaviour of the ZrC powder pre-coat and the 145Cr6 steel substrate during laser processing

The paper presents both the production method and its impact on selected properties of composite coatings reinforced with hard ZrC particles. The Fe/ZrC coatings were produced using diode laser by remelting the pre-coat in the form of paste consisting of ZrC powder and binder. Different values of laser beam power (500 W, 700 W, and 900 W) and different pre-coat thicknesses (100 µm, 150 µm, and 200 µm) were used to produce the composite coatings. During all processes, the scanning speed of laser beam was 3 m/min. Laser beam spot diameter was 1 mm. Microstructure study, microhardness tests, as well as EDS and XRD analysis were carried out. The obtained Fe/ZrC coatings were also tested for the effect of the corrosive medium in a 3.5% NaCl water solution. The effect of applied parameters on wear resistance of Fe/ZrC coatings was also studied. The tribological properties were assessed both by mass loss measurement and by scanning electron microscopy. Fe/ZrC coatings produced using the highest thickness of the pre-coat were characterised by cracks arising during production process. The very high concentration of carbides and hence high hardness of the coating produced in this way contributed to it. However, a positive effect of laser beam power increase on reduction of these cracks was observed. The coatings were characterised by very high hardness, reaching in some cases even more than 2000 HV. It was found that the most favourable properties regarding both tribology and corrosion resistance were obtained for Fe/ZrC coatings produced using 150 µm of pre-coat thickness.

Study on hard rock particle size division based on Mars rover traction performance

To simplify the dynamic solution of the contact between the rigid wheel of Mars rover and the spherical hard stone on the mixed terrain, a model for hard stone particle size division based on the traction performance of Mars rover is proposed. On the mixed terrain of hard rock and soft soil, the movement of hard rock will affect the traction performance of the rigid wheels of Mars rover. According to the different effects of the hard stones on the traction performance of rigid wheels, stones are divided into three types. The static sinkage of rigid wheels is calculated according to the Bekker bearing model, and the calculation formula of sliding sinkage of rigid wheels and hard stone sinkage is proposed. The type of hard stones is determined by comparing the sinkage of hard stones and rigid wheels. Finally, three kinds of hard stones with slip ratios of 0.2, 0.5, and 0.7 were substituted into the single wheel simulation platform and the soil trough experiment platform for simulation and experiment. The results show that on mixed terrain, the error of simulation and experimental results of fixed hard stones under three slip rates is below 5.4%, the error of drawbar pull in simulation and experimental results of movable hard stones is above 126%, and the error of simulation and experimental results of scattered small hard stones is below 2%, which verifies the effectiveness of the hard stone particle size division model.

A comprehensive analysis of the erosion in a carbon steel boiler tube elbow through the use of 3D mapping of the corroded surface and CFD modeling

Erosion corrosion is a common problem that affects boiler tubes, particularly those in power plants and industrial settings where hard water and abrasive particles are present in the flow. These particles can cause physical erosion to the surface of the tubes, which can then lead to further corrosion. This type of corrosion is often accelerated by the high temperatures and pressures present in a boiler system, as well as the presence of oxygen. The combination of physical erosion and chemical corrosion attack can cause significant damage to the tubes, reducing their ability to efficiently transfer heat and potentially leading to system failure. Therefore, it is important to predict rates of erosion to prevent costly and potentially dangerous failures. The focus of this paper is an investigation into the effects of erosion caused by hard water particles on a carbon steel boiler tube elbow (ANSI 16.9). A semi-empirical procedure, which considers properties of the material and flow parameters, is developed for predicting erosion rates. The study revealed that the primary erosion damage occurred on the extrados of the bend. The findings indicated that particles within the flow began to separate from the front wall surface, resulting in significant erosion along the lateral sides. The disappearance of erosion from the front surface of the bend was also consistent with the erosion patterns observed on the eroded pipe sample, which was extracted from the line. Moreover, it was demonstrated the presence of two different erosion patterns in the separation region, which matched qualitatively the erosion pattern observed on the sample wall.

Development and characterization of titanium oxide filled ramie fiber based hybrid composites

AbstractThis investigation aims to develop and characterize a class of multi‐phase hybrid composites consisting of bi‐directional ramie fibers, epoxy resin and micro‐sized titania (TiO2) particles in different proportions. Conventional hand layup technique is followed for fabrication of these composite slabs with fixed fiber fraction but different filler loadings of 0, 10, 20, and 30 wt%. The composites are subjected to different physical, compositional, and mechanical characterization tests under controlled laboratory conditions. The microstructural features of the composites are studied using scanning electron microscopy and stereo‐microscopy. For the compositional analysis, Fourier transform‐infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) technique are adopted. The functional groups present in the constituent materials are identified and so also the different phases in the composites. The different characterization tests reveal that with the incorporation of hard titania particles, the tensile, flexural, inter‐laminar shear strength, hardness, and impact strength improve. Similarly, the density and moisture absorption behavior are also found to be greatly affected by the inclusion of fillers. Armed with reasonably good mechanical properties and improved hardness, these epoxy‐ramie composites filled with titania micro‐particles may possibly find applications as functional materials in potential areas like wear prone situations.Highlights Hybridization of ramie‐epoxy composite by additional reinforcement of TiO2. Physical properties of the composites are affected by the inclusion of fillers. Mechanical properties of composites improved with filler content. The developed composites can be used for wear resistant applications.

Optimization of stir casting and drilling process parameters of hybrid composites

AA2219 alloy is widely used in aerospace and automobile applications, wherein the properties can be enhanced with 15% wt. of B4C reinforcement particles. Assembly task in aerospace application requires drilling millions of holes, and it is often challenging to obtain good-quality drilled holes due to the presence of hard B4C particle reinforcements. The self-lubricating capability of molybdenum disulfide (MoS2) and Graphene (Gr) materials was used as secondary reinforcements to improve the drilled hole quality characteristics. The stir-casting route fabricates the hybrid composites (AA2219 alloy/B4C/Gr/MoS2). The hardness and wear resistance properties of hybrid composites are affected by the influencing process variables such as percent reinforcement of Gr and MoS2, stirring speed, and pouring temperature. Taguchi L9 matrix is used for experimentation and performs statistical analysis. All stir-casting variables are found to make significant contributions toward hardness and wear resistance. The limitation of the Taguchi method to solve multiple objective optimizations is solved by applying Data Envelopment Analysis Ranking (DEAR) method. A DEAR method determined optimal conditions (Gr and MoS2: 1.5 wt%, stir speed: 400 rpm, and pouring temperature: 760 °C) resulted in a reduced wear rate of 1.65 × 10−3 mm3/min and 128 HV hardness in hybrid composites. The hybrid composites were prepared for the determined optimal stir casting conditions. Drilling experiments were carried out to analyze the variables such as feed rate (FR), drilling speed (DS), and drill tool material (DM): high-speed steel: HSS, carbide: C, and coated carbide: CC that affect the hybrid composite hole quality characteristics such as burr height: BH, material removal rate: MRR, and thrust force: TF. A DEAR method determined optimal drilling conditions (FR: 0.25 mm/rev; DS: 20 m/min; DM: coated carbide drill tool) resulted in 645 mm3/min of MRR, 2.95 kN for TF, and 0.16 mm for BH, respectively. The self-lubricating capability of Gr and MoS2 reinforcement particles in hybrid composites ensures excellent composite properties and drilled-hole quality characteristics. Taguchi and DEAR methods employ simple mathematical steps which can be used by novice industry personnel to perform optimization for other output characteristics.

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

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