Extreme Hardness Research Articles

Structure, Stability, and Electronic Properties of Boron Suboxide: A Density Functional Theory Study

Boron suboxide (B6O) is a boron-rich compound derived from the α-rhombohedral boron lattice with extreme hardness and unusual semiconducting properties. In this work, density functional theory (DFT) was used to show that unit cell volume, mechanical strength, band gaps, and thermodynamic stabilities of B6O were influenced by the interstitial elements and point defects at the icosahedral sites. While the hexagonal unit cell volume (HUCV) varies with interstitial occupancy, it is the icosahedral defect that weakens the intrinsic bulk modulus of B6O. Using the hybrid HSE functional, we confirmed that the perfect B6O bulk is a p-type semiconductor with a direct band gap of 2.8 eV. Furthermore, by screening α-boron compounds systematically, we found that a simple octet rule may offer a consistent explanation for the variations in the computed electronic structures. The formation free energies calculated over a wide range of temperatures (0–2500 K) and pressures (0–80 GPa) predict that formations of interstitial defects become favorable only at higher temperatures (ca. 1800 K) in bulk B6O lattices. The nudged elastic band (NEB) method was employed to identify the minimum energy pathways for the diffusions of dislocated B and O atoms. The diffusion of icosahedral B atoms has an energy barrier of 0.16 eV. More complex B diffusion paths involving the reorganization of icosahedral boron atoms incur higher barriers (>1 eV). In contrast, the diffusion of interstitial O atoms is facile with a barrier of 0.4 eV. Lastly, successive O insertions into the α-B lattice were performed using DFT to generate a basic understanding of the oxidation process. These calculations provide fundamental atomistic insights into the growth of B6O crystals and control of their point defects.

Synthesis and characterization of titanium nitride nanoparticles

Titanium nitride (TiN) materials have gained an interest over the past years due to their unique characteristics, such as thermal stability, extreme hardness, low production cost, and comparable optical properties to gold. In the present study, TiN nanoparticles were synthesized via a thermal benzene route to obtain black nanoparticles. Scanning electron microscopy (SEM) was carried out to examine the morphology. Further microscopic characterization was done where the final product was drop cast onto double-sided conductive carbon tape and sputter-coated with gold/palladium at a thickness of 4 nm for characterization by field emission scanning electron microscopy (FE-SEM) with energy dispersive X-Ray spectroscopy (EDS) that revealed they are spherical. ImageJ software was used to measure the average size of the particles to be 79 nm in diameter. EDS was used to determine the elements present in the sample and concluded that there were no impurities. Further characterization by Fourier Transform infrared (FTIR) spectroscopy was carried out to identify the characteristic peaks of TiN. X-ray diffraction (XRD) revealed typical peaks of cubic phase titanium nitride, and crystallite size was determined to be 14 nm using the Debye-Scherrer method. Dynamic light scattering (DLS) analysis revealed the size distribution of the TiN nanoparticles, with nanoparticles averaging at 154 nm in diameter. Zeta potential concluded the surface of the TiN nanoparticles is negatively charged.

Experimental investigation on the reformation and strength weakening of hard limestone by acidizing

Several derivative disasters such as ground pressure disasters and methane explosions can be caused by the hard roof in coal mines. For limestone roofs with fine integrity and extreme hardness, collapse is difficult and the effect of conventional roof control methods is limited. Acidizing reformation is an effective way to weaken the strength of roof strata based on acid-rock reaction. In this study, the rock strength damage law and acid reaction characteristics were tested by the limestone acidification experiment. Besides, the strength degradation mechanism of limestone under the acidity effect was analyzed. The results show that the acid corrosion characteristics of limestone are obvious, as numerous mineral grains generate voids under the effects of acid corrosion, and more defects are formed inside. The acid-rock reaction is the most intense at the early stage and then gradually reaches dynamic equilibrium, and the acid corrosion rate of limestone is 4.24% (10% HCl, 360 min). The hard limestone is damaged after acidification. Furthermore, the internal cracks can be induced to rapid initiation and unstable propagation under load, which reduces the strain required for rock failure by 33.33%. The failure morphology is more complicated, and the uniaxial compressive strength and elastic modulus decrease by 52.42% and 34.44% respectively. The strength weakening of hard roof after acidification is due to the defects such as intergranular cracking caused by the corrosion of rock crystals under acidity effect, which accelerate the initiation and propagation of internal cracks with external force. Macroscopically, acidification induced the deterioration of rock mechanical properties by reforming the roof structure. The feasibility of acidizing reformation method to control hard roof is confirmed in this study.

Anomalous bond softening mediated by strain-induced Friedel-like oscillations in a BC2N superlattice

The crystal structure of ${\mathrm{BC}}_{2}\mathrm{N}$ and the origin of its superhardness remain under constant debate, hindering its development. Herein, by evaluating the x-ray diffraction pattern, the thermodynamic stability at normal and high pressures of a series of ${\mathrm{BC}}_{2}\mathrm{N}$ candidates, the (111) $\mathrm{B}{\mathrm{C}}_{2}{\mathrm{N}}_{2\ifmmode\times\else\texttimes\fi{}2}$ superlattice (labeled $\mathrm{R}2u\ensuremath{-}\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$) is identified as the realistic crystal structure of the experimentally synthesized ${\mathrm{BC}}_{2}\mathrm{N}$. We further reveal that the strain-induced Friedel-like oscillations dominates the preferable slip systems of $\mathrm{R}2u\ensuremath{-}\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$ by drastically weakening the heterogenous bonds across the slip plane and thus leads to its ultralow dislocation slip resistance, which originates from the metallization triggered by the reduction in energy separation between bonding and antibonding interactions of the softened bonds. Our results rule out $\mathrm{R}2u\ensuremath{-}\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$ as the intrinsic superhard material surpassing $c\text{\ensuremath{-}}\mathrm{BN}$, whereas the experimentally determined extreme hardness can be attributed to the nanocrystalline grains glued by interfacial amorphous carbon which provides a strong barrier for plastic deformation. These findings provide a view of the longstanding issue of the possible structure of experimentally observed ${\mathrm{BC}}_{2}\mathrm{N}$, and establish a mechanism underlying the strain-driven electronic instability of superlattice structures, providing guidance towards rational design of superhard materials.

Third and fourth generation ceramic-on-ceramic total hip arthroplasty at a minimum of ten years

BackgroundCeramic on Ceramic bearings in Total Hip Arthroplasty (THA) afford a low friction coefficient, low wear rates and extreme hardness. Significant complications include hip squeak, ceramic fracture and poor polyethylene performance in revision procedures due to imbedding of abrasive microscopic ceramic fragments. We report on the results of this bearing at a minimum of 10 years. MethodsA single-centre retrospective review of 449 THAs was performed. Primary outcome measures included aseptic revision and all-cause revision rates at a minimum of 10 years post operatively. Evaluation of functionality was performed with WOMAC and SF-36 scores which were performed pre-operatively and at intervals of 6 months, one year, 2 years, 5 years and 10 years post operatively. ResultsThere was a 6.2% (n = 28) all-cause and 5.3% (n = 24) aseptic revision rate for ceramic on ceramic total hip arthroplasty at minimum of 10 years with a mean time to revision 4.8 years (range 2 months–11.6 years). Notably, there were 2 revisions for ceramic head fracture, one for ceramic liner fracture, 3 for aseptic loosening and 3 revisions for squeaking. Pain of unknown origin was the most common reason for revision. There was an improvement in postoperative WOMAC scores from a mean of 59.8 (range 15–95) pre-operatively to a mean of 15.6 (range 0–78) at 10 years. ConclusionThis study showed good functional outcomes but high revision rates for CoC THA at a minimum of 10 years. Our rates of ceramic fracture were consistent with other studies.

Wear behaviors of cubic boron nitride tools with various binders in high-speed turning of compacted graphite irons

Compacted graphite iron (CGI) is a promising material as diesel engines in automotive industry, but the poor machinability and low machining efficiency have further hindered the employment of CGI in the potential applications. Cubic boron nitride (cBN), possessing extreme hardness and chemical inertness, is the best candidate as tools to machine ferrous metals. In this paper, we attempt to explain the disparities in wear behaviors of cBN tool with different binders by implementing high-speed turning of CGI. The effects of various binders on cBN tool flank wear, cutting force, cutting temperature, and machined surface roughness was systematically investigated. Additionally, the response relationship among flank wear, cutting force, temperature and surface roughness was obtained. Further, the underlying reasons of the wear mechanism of cBN tool were revealed. The results indicated that the cBN tool performances strongly depend on the affinity of binders with CGI. The contributions of binder phases, cBN content, and cBN grain size under the employed machining conditions: the binders are dominated, and followed by cBN grain size or cBN content in the high-speed cutting of CGI. The small cBN grain size, and TiCN, TiC, TiN binders of cBN tools have superior cutting performance than the Co binders.

Wear and friction analysis of cubic boron nitride tools with different binders in high-speed turning of nickel-based superalloys

Nickel-based superalloy is an attractive material as turbine engine components in aerospace industry, but low machining efficiency and poor machinability have further hindered it to be widely employed in potential applications. Cubic boron nitride (cBN), possessing extreme hardness and chemical inertness, is the potential candidate as tools to machine superalloys. In this work, we attempt to explain the disparities in wear and friction behaviors of various-binder cBN tools by performing high-speed turning Inconel 718. Tool wears both the rake face and flank face are systematically analyzed. Friction coefficients between cBN and Inconel 718 were determined. Tool flank temperature distributions with different flank wear (VB) were visually presented by FEM simulations.

Experimental and simulation approach of surface generation on K-80 alumina ceramic by recently developed sustainable FB-HAJM using novel nozzle design

K-80 alumina ceramic makes it challenging to machine them economically due to extreme hardness. Fluidized bed-hot abrasive jet machining (FB-HAJMing), in which a target profile is eroded by the impingement action of air-hot abrasive jet, which containing fine hot abrasive grains for machining of K-80 alumina ceramic materials without thermal damage. This study is intended to analyse kerf angle (KA), surface roughness (Rz) and material removal rate (MRR) using HAJMing process of K-80 alumina ceramic. Fifteen sets of experimental trials were conducted two times using tungsten carbide (WC) nozzle with and without internal thread. The identified three cutting parameters i.e., air pressure (P), abrasive temperature (T) and stand-off-distance (SOD), were considered for experimental design. Furthermore, the response surface methodology (RSM), statistical techniques (here, desirability function approach) followed by computational approach (here, genetic algorithm) are respectively employed for experimental investigation, predictive modelling and multi-objective optimization. Subsequently, confirmation tests evaluate the efficiency of the suggested two multi---objective optimization methods to rationalize the utility and awareness of the usefulness of hot abrasives in HAJMing. Moreover, computational fluid dynamics (CFD) modelling was utilized to develop a comprehensive relation between HAJMed profile geometry and erosive flow. Finally, the environmental ‘Pugh Matrix’ approach is proposed for the HAJMing process sustainability evaluation. The results indicated a desire to improve the cutting efficiency for material erosion by using hot abrasives in the HAJMing procedure. The most important parameter for surface roughness is abrasive temperature, while pressure is important for both KA and MRR. The use of hot abrasives in the FB-HAJM process has demonstrated a focus on improving the cutting performance for material removal. From an economic standpoint, the current study presents a technological criterion for feasible industrial applications of the FB-HAJM method, such as in aerospace, precision manufacturing, and biomedical field.

Modeling and simulation of interstitial fluid flow around an osteocyte in a lacuno-canalicular network

Experiments have shown that external mechanical loading plays an important role in bone development and remodeling. In fact, recent research has provided evidence that osteocytes can sense such loading and respond by releasing biochemical signals (mechanotransduction, MT) that initiate bone degradation or growth. Many aspects on MT remain unclear, especially at the cellular level. Because of the extreme hardness of the bone matrix and complexity of the microenvironment that an osteocyte lives in, in vivo studies are difficult; in contrast, modeling and simulation are viable approaches. Although many computational studies have been carried out, the complex geometry that can involve 60+ irregular canaliculi is often simplified to a select few straight tubes or channels. In addition, the pericellular matrix (PCM) is usually not considered. To better understand the effects of these frequently neglected aspects, we use the lattice Boltzmann equations to model the fluid flow over an osteocyte in a lacuno-canalicular network in two dimensions. We focus on the influences of the number/geometry of the canaliculi and the effects of the PCM on the fluid wall shear stress (WSS) and normal stress (WNS) on an osteocyte surface. We consider 16, 32, and 64 canaliculi using one randomly generated geometry for each of the 16 and 32 canaliculi cases and three geometries for the 64 canaliculi case. We also consider 0%, 5%, 10%, 20%, and 40% pericellular matrix density. Numerical results on the WSS and WNS distributions and on the velocity field are visualized, compared, and analyzed. Our major results are as follows: (1) the fluid flow generates significantly greater force on the surface of the osteocyte if the model includes the pericellular matrix (PCM); (2) in the absence of PCM, the average magnitudes of the stresses on the osteocyte surface are not significantly altered by the number and geometry of the canaliculi despite some quantitative influence of the latter on overall variation and distribution of those stresses; and (3) the dimensionless stress (stress after non-dimensionalization) on the osteocyte surface scales approximately as the reciprocal of the Reynolds number and increasing PCM density in the canaliculi reduces the range of Reynolds number values for which the scaling law holds.

Glassy phase influence on the optical finishing of sintered silicon carbide with Al2O3 and Y2O3

Developing low-roughness silicon carbide (SiC) mirror surfaces for aerospace applications is challenging due to their extreme hardness and brittle nature. In this work, liquid phase sintered silicon carbide (LPS-SiC) substrates were machined at different feed rates. The influence of the glassy phase on the final finishing process was evaluated. An innovative thermo-chemical etching was proposed to evince the glassy phase. X-ray diffraction (XRD) analysis revealed the change of crystal structure from β-SiC to α-SiC in addition to the presence of YAP and YAG phases, constituents of the glassy phase. Vickers microhardness and scratch tests simulating the action of a single diamond grain on the surface of the substrates with and without the glassy phase showed that the hardness of the SiC grain and its fracture resistance exceeded the values obtained for the substrate with the glassy phase by 110% and 170% respectively. Reducing the feed rate decreased the damage to the surface of the substrate with the glassy phase by 25% and to the SiC matrix by 90%.

Mechanical properties of room-temperature injection molded, pressurelessly sintered boron carbide

Boron carbide (B4C) is of interest in the armor community due to its combination of extreme hardness and low density. However, it is difficult to utilize these properties in many applications due to the challenges associated with forming near-net shapes of B4C, combined with its low inherent sinterability without the application of external pressure. In this study, highly loaded (51 vol. %) aqueous B4C suspensions were developed and injection molded at room temperature followed by pressureless sintering up to 2075 °C. Three different sintering aids (Y2O3, Al, and Al2O3) were used to aid the densification process. B4C parts were sintered to high density (up to 97.7% relative density) and high hardness values (up to 3200 Vickers). The flexural strength of the samples was limited by grain pullout during polishing of the tensile surface; the strength was correlated to the maximum grain pullout flaw measured at the intersection of the tensile surface and the fracture surface (R2 > 0.98). The robust performance of the B4C suspensions and their resulting densities and hardness demonstrate the room-temperature injection molding process as a viable alternative for low-cost near-net shaping of B4C components.

Comparative study of the MeV ion channeling implantation induced damage in 6H-SiC by the iterative procedure and phenomenological CSIM computer code

Due to its unique material properties, such as extreme hardness and radiation resistance, silicon carbide has been used as an important construction material for environments with extreme conditions, like those present in nuclear reactors. As such, it is constantly exposed to energetic particles (e.g., neutrons) and consequently subjected to gradual crystal lattice degradation. In this article, the 6H-SiC crystal damage has been simulated by the implantation of 4 MeV C3+ ions in the (0001) axial direction of a single 6H-SiC crystal to the ion fluences of 1.359 1015 cm-2, 6.740 1015 cm-2, and 2.02 1016 cm-2. These implanted samples were subsequently analyzed by Rutherford and elastic backscattering spectrometry in the channeling orientation (RBS/C & EBS/C) by the usage of 1 MeV protons. Obtained spectra were analyzed by channeling simulation phenomenological computer code (CSIM) to obtain quantitative crystal damage depth profiles. The difference between the positions of damage profile maxima obtained by CSIM code and one simulated with stopping and range of ions in matter (SRIM), a Monte Carlo based computer code focused on ion implantation simulation in random crystal direction only, is about 10%. Therefore, due to small profile depth shifts, the usage of the iterative procedure for calculating crystal damage depth profiles is proposed. It was shown that profiles obtained by iterative procedure show very good agreement with the ones obtained with CSIM code. Additionally, with the introduction of channeling to random energy loss ratio the energy to depth profile scale conversion, the agreement with CSIM profiles becomes excellent.

An experimental analysis on surface roughness of the selective laser sintered and unsintered Inconel 718 components using vibratory surface finishing process

The selective laser sintering (SLS) is one among the most fast emerging rapid prototyping processes, primarily due to its capability to produce component using different kind of raw materials. On the other hand, because of stair stepping effect the prototypes produced by SLS technique have moderately high surface roughness. Vibratory finishing is the multifunctional process is utilized in several engineering industries internationally for various applications like fine finishing, brightening, cleaning, and radiusing of components. In the present research work, due to excellent mechanical properties Inconel 718 powder particles were used as raw materials to produce component using SLS technique. The surface roughness of the components (both sintered and unsintered) were analyzed by subjected them to vibratory surface finishing process using different media under constant amplitude of 0.8 mm and frequency of 25 Hz, 50 Hz, and 75 Hz for different processing time in minutes. The surface roughness tester was used to anlyse the surface roughness of the components after vibratory finishing test. The surface morphology was examined using scanning electron microscope and EDAX. The Vicker’s micro hardness tester was used to know the surface roughness of the components, laser sintered samples shows extreme hardness as compared to unsintered samples [17]. The experimental results confirm that, the surface roughness of the laser sintered and unsintered samples was reduced at 75 Hz as compared to lower taken frequencies. However, laser sintered sample performed well as compared to unsintered samples due to high density, less porosity and high surface hardness.

Comparison of coated and uncoated HSS drill bit on surface roughness, material removal rate and dimensional accuracy of SS410 stainless steel

Stainless Steel 410 (SS410) is 12% chromium martensitic steel which can be heat treated to obtain wide range of mechanical properties. Due to its high corrosion resistance and excellent combination of toughness and strength, it is used for furnace parts, steam turbine buckets, blades, pump, nozzle, automotive parts, aerospace application etc. Considering the challenges in machining of this material, drilling experiments were conducted on SS410 to analyse the effect of various parameters. Coatings always have a positive influence on the tool. It helps to reduce friction in the cut, reducing heat build-up in the drill bit, as well as improving the flow of material out of the drilling point. It also delivers protection against corrosion, rust and water damage. The AlTiN coating provides exceptional oxidation resistance and extreme hardness. This coating works well in very demanding cutting tool applications, especially when tools are being pushed to the max. This paper reports on the investigation of performance of Al-Ti-N coated and uncoated HSS drill bits when drilling SS410. Machining characteristics studied in this investigation include Material Removal Rate (MRR), Surface Roughness (Ra), Ovality. Drilling tests were carried out as per Taguchi’s L16 array using process parameters such as Speed (30, 40, 50, 60 m/min), Feed (F) (0.05, 0.075, 0.1, 0.125 mm/rev) and point angle (P) (100, 110, 120, 130 degree). Comparison of the performance of coated and uncoated drill bits showed that coated drill bits have higher performance than uncoated. By using coated drills surface Roughness and Ovality values of drilling are reduced to an extend of 48.5% and 2%. Material removal rate value is also improved to an extend of 23%.

Boron Doped Diamond for Real-Time Wireless Cutting Temperature Monitoring of Diamond Coated Carbide Tools.

Among the unique opportunities and developments that are currently being triggered by the fourth industrial revolution, developments in cutting tools have been following the trend of an ever more holistic control of manufacturing processes. Sustainable manufacturing is at the forefront of tools development, encompassing environmental, economic, and technological goals. The integrated use of sensors, data processing, and smart algorithms for fast optimization or real time adjustment of cutting processes can lead to a significant impact on productivity and energy uptake, as well as less usage of cutting fluids. Diamond is the material of choice for machining of non-ferrous alloys, composites, and ultrahard materials. While the extreme hardness, thermal conductivity, and wear resistance of CVD diamond coatings are well-known, these also exhibit highly auspicious sensing properties through doping with boron and other elements. The present study focuses on the thermal response of boron-doped diamond (BDD) coatings. BDD coatings have been shown to have a negative temperature coefficient (NTC). Several approaches have been adopted for monitoring cutting temperature, including thin film thermocouples and infrared thermography. Although these are good solutions, they can be costly and become impractical for certain finishing cutting operations, tool geometries such as rotary tools, as well as during material removal in intricate spaces. In the scope of this study, diamond/WC-Co substrates were coated with BDD by hot filament chemical vapor deposition (HFCVD). Scanning electron microscopy, Raman spectroscopy, and the van der Pauw method were used for morphological, structural, and electrical characterization, respectively. The thermal response of the thin diamond thermistors was characterized in the temperature interval of 20–400 °C. Compared to state-of-the-art temperature monitoring solutions, this is a one-step approach that improves the wear properties and heat dissipation of carbide tools while providing real-time and in-situ temperature monitoring.

Electrostatic Self-Assembled Composite Abrasives for Chemical Mechanical Polishing of A-Plane Sapphire

Sapphire substrates with different orientations have wide applications due to their excellent physical, chemical and optical properties. However, the chemical mechanical polishing of sapphire is challenging due to its chemical inertness, extreme hardness and brittleness. Herein, chemical mechanical polishing of A- and C-plane sapphire was systematically studied using α-Al2O3 and silica abrasives and polishing mechanism was analyzed by X-ray photoemission spectroscopy (XPS) and nanoindentation meter. The high MRR selectivity for C-plane sapphire in α-Al2O3 slurry is the synergy of selective hydration of C-plane and stronger crystal structure of A-plane. The low MRR selectivity for C-plane sapphire in silica slurry can be attributed to the formation of Al2SiO5 on both planes which reduced the impact of strong mechanical effect of α-Al2O3 abrasives. To improve the MRR of A-plane sapphire, a new nanocomposite particle with alumina as the core and silica as the soft shell was prepared by an electrostatic self-assembly method. The new composite abrasives combined the mechanical effect of α-Al2O3 abrasives and chemical effect of silica abrasives and demonstrated substantially higher MRR for A-plane sapphire than pure alumina abrasives, pure silica abrasives and physical mixture of alumina+silica abrasives.

Effects of TiAl Alloy as a Binder on Cubic Boron Nitride Composites.

Owing to their extreme hardness, cubic boron nitride (cBN) composites are widely used in cutting applications. The performance of cBN composites is closely related to the characteristics of the binder. Therefore, novel binders must be developed to improve the performance of cBN composites. In the present work, TiAl intermetallics were used as binders to fabricate cBN composites by employing a high-temperature and high-pressure sintering method. The phase transformation, sintering reaction mechanism, thermal stability, and mechanical properties of the resultant cBN composites were investigated. It was found that during the sintering process, Ti atoms preferentially reacted with boron nitride particles, whereas Al atoms enriched and transformed into TiAl3 phases and formed cBN/AlN, AlB2/TiN, and TiB2/TiAl3-layered structures eventually. The composites maintained good oxidation resistance at 1200 °C. A decrease in the particle size of the TiAl binder improved the uniformity of particle size distribution and increased the flexural strength of the composites.

RAW WATER QUALITY ANALYSIS TO DISCOVER THE CAUSE OF PIPELINE SCALLING PROBLEM IN PT. X (ICE PRODUCTION COMPANY)

PT. X is one of the ice companies in which its largest company is located in Bali, more precisely in the Pidada area, North Denpasar. Based on field observations the area is an area that has a calcareous soil structure. The water source of PT. X was extracted from the groundwater. From the field observation, it was found that the pipeline network, that connected the inlet water to water treatment system and ice production units, was severely covered by faint white scale. In order to discover the origin of this scale, water quality testing need to be carried out. From the results, it was found that the total hardness in the inlet water, taken from the groundwater tap, was 162.85 mg/l with calcium concentration of 2.15 mg/l and iron 3.83 mg/l. Water quality testing was also carried out in the water treatment unit consisting of resin softener where the total hardness surprisingly increased into 279.81 mg/l, calcium concentration was 2.96 mg/l, iron concentration was 0.55 mg/l. Even after being treated in softener resin, the total hardness increased sharply to 483 mg/l, which categorized as extreme hardness. The increase in total hardness indicates that there was a failure in the operation of the water treatment system, even it also contributed to the higher hardness and calcium concentration. This over-year’s treatment failure has been causing accumulation of hardness and calcium concentration in the compartment of both water treatment system and ice production unit that inflicts a higher hardness level in the effluent.

Porosity effect on the tribological properties of Al-Si alloys for diamond-like carbon coating of cold sprayed

In this study, diamond-like carbon (DLC) coating made from spherical powder SP and Irregular powder IP manufactured for plasma of cold sprayed by gas atomization is presented. Sliding assessment is carried out at different loads on each DLC coating. All DLC coating surfaces are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, coatings show low porosity and extreme hardness. Irregular powder IP coatings have proved to be less hardness than SP coatings. In case of IP coatings, abrasive plowing with used particles is resulted in an increased wear, while the available porosity in SP of the used particles is formed in some points of reduced sliding of wear. Coatings of IP cause an increasing of coefficient of friction (CoF). The load limitations are associated with tribooxidation in IP coatings, while mixed particles together with tribooxidation result in lower CoF with SP coatings. The range of CoF for all test parameters is 0.24–0.32. Transmission electron microscopy (TEM) shows characteristics body-filled pores composed of a deformed material with an ultrafine microstructure and micron-sized particles. The characterization confirms that 30% of pore-filled coatings are ultra-deformed fabric with microstructure and particles, while the worn surfaces have a rough microstructure. The effects confirm that SP hardness and porosity help attract particles and reduce abrasiveness.

Design of an innovative new extrusion system for a printing machine for ceramics

The introduction of ceramic materials in the medical field is becoming a vital necessity because of its stable physicochemical characteristics, high biocompatibility, and good osteoconductivity. On the contrary, machining ceramic components is difficult, owing to their extreme hardness and brittleness. Additive manufacturing (AM) technologies are an appropriate alternative to obtain the complex shapes of implants, which can have porous structures. Thus, since the development of 3D printing, direct ink writing (DIW) is one of the most promising and inexpensive techniques for shaping free-form ceramic medical components such as prostheses or dental implants from liquids or pastes. However, the assurance of performance criteria of the extrusion system for simultaneous usage becomes the major challenge for most direct ink writing (DIW) platforms, for instance for printing large parts, for multi-material printing, to decrease printing time, and to increase efficiency in terms of motor usage and weight of the extruders. To address the current deficiencies, a new extrusion system is designed for a 3D printing machine for ceramics that is compatible with different low-cost, open-source 3D printers. The proposed extrusion model enables printing with a loader with different syringes simultaneously, without stopping the operational process while switching the syringe. It adopts three subsystems. The automatic syringe loading system, which is operational to manually receive several syringes of the same or different volumes, allows the syringe feeding system to be loaded and unloaded once the syringe is empty. The syringes are automatically transferred to the holding system using an arm. The holding system allows the fixing of the syringe in order to perform printing with ceramic material. Pugh concept analysis was used to select the optimum design shape. After that, the 3D CAD environment was used to combine the strength of Pugh’s method and the design space. This brings a new concept into the mechanical design field for 3D printers, which is in line with the technological trends prevalent in the industry.