Search Results (330)

Background: Compared to the conventional method of machining granite, abrasive water jet machining (AWJM) offers several benefits, including flexible cutting mechanisms and machine efficiency, among other possible advantages. The high-speed particles carried by water remove the materials, preventing heat damage and maintaining the granite’s structure. Methods: Three types of granite with different compressive strengths are investigated in terms of the effects of pump pressure (P), traverse speed (T), and abrasive mass flow (A) on the cutting depth. Results: The results of the study demonstrated that the coarse-grained granite negatively affected the penetration depth, while the fine-grained granite produced a higher cutting depth. The value of an optimal depth of penetration was also generated; for example, the optimum depth obtained for Black Galaxy Granite, M1 (32.27 mm), was achieved at P = 300 MPa, T = 100 mm/min, and A = 180.59 g/min. Conclusions: In terms of processing parameters, the maximum penetration depth can be achieved in granite with a higher compressive strength. Full article

The high-efficiency polishing of large-sized polycrystalline diamond (PCD) wafers continues to pose significant challenges in its practical applications. Conventional mechanical polishing suffers from a low material removal rate (MRR) and surface damage. To improve the process efficiency, this study investigates the effect of chemomechanical abrasive polishing (CMAP) with a slurry containing high-concentration H₂O₂ and varying mass percentages of SiO₂ powder and diamond particles on surface morphology, surface roughness, material removal rate (MRR), and microstrain of PCD disks. The contributions of mechanical action, chemical action, and bubble cavitation to the CMAP process are analyzed. Scanning electron microscopy (SEM) observations indicate that large grains present in PCD are effectively eliminated after CMAP, leading to a notable reduction in surface roughness. The optimal results are obtained with 60 wt% SiO₂ powder and 40 wt% diamond particles, achieving a maximum MRR of 1039.78 μm/(MPa·h) (15.5% improvement compared to the mechanical method) and a minimum surface roughness (Sa) of 3.59 μm. Additionally, the microstrain on the PCD disk shows a slight reduction following the CMAP process. The material removal mechanism is primarily attributed to mechanical action (70.8%), with bubble cavitation and chemical action (27.5%) and action of SiO₂ (1.7%) playing secondary roles. The incorporation of SiO₂ leads to the formation of a lubricating layer, significantly reducing surface damage and decreasing the surface roughness Sa to 1.39 µm. Full article

An analysis of the existing methods of sintering diamond-containing composites is presented. On the basis of mathematical modeling and experimental studies, the conditions of the laser liquid-phase sintering of diamond-containing composites under which they retain their strength are determined. The energy and technological parameters of the laser irradiation process are characterized, which determine the range of laser processing modes within which no oxidation and crack formation occur, and a high-quality composite with specified geometrical parameters is formed. It has been proven that composites consisting of synthetic diamond grains and a metal bond do not lose strength under the condition that the temperature during laser heating does not exceed 1600 °C and the exposure time is 0.3 s. Electron microscopy and X-ray diffractometry were used for experimental studies of the microstructure and phase composition of the sintered layers. A new design and manufacturing method for a drum-type abrasive tool with replaceable diamond inserts for grinding large-sized aircraft and shipbuilding products are proposed. Components of a laser technological complex for the implementation of the process of sintering the diamond-containing layer of the abrasive inserts of the drum have been developed. Full article

Phonolite is a fine-grained, shallow extrusive rock rich in alkali minerals and containing iron/titanium-bearing minerals. This rock is widely used as a construction material for building exteriors due to its excellent abrasion resistance and insulation properties. However, during the cutting process, approximately 70% of the rock is discarded as tailing. So, this study aims to repurpose tailings from a phonolite cutting and sizing plant into a high-alkali ceramic raw mineral concentrate. To enable the use of phonolite tailings in ceramic manufacturing, it is necessary to remove coloring iron/titanium-bearing minerals, which negatively affect the final product. To achieve this removal, dry/wet magnetic separation processes, along with flotation, were employed both individually and in combination. The results demonstrated that using dry high-intensity magnetic separation (DHIMS) resulted in a concentrate with an Fe₂O₃ + TiO₂ grade of 0.95% and a removal efficiency of 85%. The wet high-intensity magnetic separation (WHIMS) process reduced the Fe₂O₃ + TiO₂ grade of the concentrate to 1.2%, with 70% removal efficiency. During flotation tests, both pH levels and collector concentration impacted the efficiency and Fe₂O₃ + TiO₂ grade (%) of the concentrate. The lowest Fe₂O₃ + TiO₂ grade of 1.65% was achieved at a pH level of 10 with a collector concentration of 2000 g/t. Flotation concentrates processed with DHIMS achieved a minimum Fe₂O₃ + TiO₂ grade of 0.90%, while those processed with WHIMS exhibited higher Fe₂O₃ + TiO₂ grades (>1.1%) and higher recovery rates (80%). Additionally, studies on flotation applied to WHIMS concentrates showed that collector concentration, pulp density, and conditioning time significantly influenced the Fe₂O₃ + TiO₂ grade of the final concentrate. Full article

Nickel matrix composites reinforced with T15 high-speed steel (HSS) were prepared using powder metallurgy techniques. A systematic investigation was conducted into the effect of CeO₂, MoS₂, and graphite additives on the tribological properties of the composites. The results show that when T15 HSS particles are added, nickel grains do not grow as much as they do in pure sintered nickel. It was also observed that the T15 HSS particles were diffusion-bonded to the nickel matrix after sintering. The highest relative density after sintering is obtained for composites containing graphite, but the maximum hardness of 243 HV can be achieved for composites containing 2% of CeO₂, which is about 16% higher than that of the Ni-T15 HSS composite. The wear rate of Ni-T15 HSS composites reduces from 3.4782 × 10⁻⁷ cm³/N∙m to 2.0222 × 10⁻⁷ cm³/N∙m as the content of CeO₂ rises from 0 wt.% to 2 wt.%. The wear mechanisms of composites with MoS₂ or graphite are abrasive wear and adhesive wear. The introduction of CeO₂ enhances the hardness of the investigated composites to the highest degree, leading to a change in the wear mechanism of the composites to slight abrasive wear. The addition of CeO₂ can effectively optimize the tribological properties of Ni-T15 HSS composites. Full article

This study investigated the erosive wear of a polyurea coating with a hardness of 95 ShA and a thickness of 3 mm applied to a 3 mm thick plate made of S235 steel. The process of erosive wear was carried out using a stream of compressed air containing abrasive grains of aluminum oxide (Al₂O₃). The erosive wear was studied using different incidence angles (45°, 60° and 90°) and erosive grain sizes. Thus, the effects of the incidence angle and erosive grain size on the erosive wear of the polyurea coating were analyzed. Erosive wear was determined as linear wear: the depth of the wear trace was measured using an optical profilometer. This study showed a non-linear correlation between erosive wear, incidence angle and erosive particle size. In addition, a qualitative study of the surface of the coating after a wear test was carried out using a scanning electron microscope, which made it possible to describe the mechanisms of erosive wear of the polyurea coating. Full article

Mold copper plates (Cr–Zr–Cu alloy) frequently fail due to severe wear under high-temperature conditions during continuous casting. To solve this problem, Inconel 718 coatings were prepared on the plate surface via laser cladding to enhance its high-temperature wear resistance. The results demonstrate that the coatings exhibit a defect-free structure with metallurgical bonding to the substrate. The coating primarily consists of a γ-(Fe, Ni, Cr) solid solution and carbides (M₂₃C₆ and M₆C). Notably, elongated columnar Laves phases and coarse Cr–Mo compounds were distributed along grain boundaries, significantly enhancing the coating’s microhardness and high-temperature stability. The coating exhibited an average microhardness of 491.7 HV_0.5, which is approximately 6.8 times higher than that of the copper plate. At 400 °C, the wear rate of the coating was 4.7 × 10⁻⁴ mm³·N⁻¹·min⁻¹, significantly lower than the substrate’s wear rate of 8.86 × 10⁻⁴ mm³·N⁻¹·min⁻¹, which represents only 53% of the substrate’s wear rate. The dominant wear mechanisms were adhesive wear, abrasive wear, and oxidative wear. The Inconel 718 coating demonstrates superior hardness and excellent high-temperature wear resistance, effectively improving both the surface properties and service life of mold copper plates. Full article

In response to the performance requirements of ship conductive rings in the coupled environment of high salt spray, high humidity, and mechanical wear in the ocean, a Cu-TiC composite coating was prepared on the surface of 7075 aluminum alloy by using the high-speed laser cladding (HLC) technology. The influence laws of the scanning speed (86.4–149.7 mm/s) on the microstructure, tribological properties, and corrosion resistance of the coating were explored. The results show that the scanning speed significantly changes the phase composition and grain morphology of the coating by regulating the thermodynamic behavior of the molten pool. At a low scanning speed (86.4 mm/s), the CuAl₂ phase is dominant, and the grains are mainly columnar crystals. As the scanning speed increases to 149.7 mm/s, the accelerated cooling rate promotes an increase in the proportion of Cu₂Al₃ phase, refines the grains to a coexisting structure of equiaxed crystals and cellular crystals, and improves the uniformity of TiC particle distribution. Tribological property analysis shows that the high scanning speed (149.7 mm/s) coating has a 17.9% lower wear rate than the substrate due to grain refinement and TiC interface strengthening. The wear mechanism is mainly abrasive wear and adhesive wear, accompanied by slight oxidative wear. Electrochemical tests show that the corrosion current density of the high-speed cladding coating is as low as 7.36 × 10⁻⁷ A·cm⁻², and the polarization resistance reaches 23,813 Ω·cm². The improvement in corrosion resistance is attributed to the formation of a dense passivation film and the blocking of the Cl diffusion path. The coating with a scanning speed of 149.7 mm/s exhibits optimal wear-resistant and corrosion-resistant synergistic performance and is suitable for the surface strengthening of conductive rings in extreme marine environments. This research provides theoretical support for the process performance regulation and engineering application of copper-based composite coatings. Full article

This study investigates the influence of Si content (x = 0, 0.1, 0.3, 0.5) on the microstructure, mechanical properties, and wear behavior of FeNiCrAl_0.7Cu_0.3Si_x high-entropy alloys. With increasing silicon content, the microstructure evolves from a dendritic morphology in the silicon-free FeNiCrAl_0.7Cu_0.3 alloy to a transitional structure in the FeNiCrAl_0.7Cu_0.3Si_0.1 alloy that retains dendritic features; then to a chrysanthemum-like morphology in the FeNiCrAl_0.7Cu_0.3Si_0.3 alloy, and finally to island-like grains in the FeNiCrAl_0.7Cu_0.3Si_0.5 alloy. This evolution is accompanied by a phase transition from an Fe and Cr-rich body-centered cubic phase to an Al and Ni-rich body-centered cubic phase, with silicon showing a tendency to segregate alongside aluminum and nickel. The microhardness increases from 498.2 ± 15.0 HV for the FeNiCrAl_0.7Cu_0.3 alloy, to 502.7 ± 32.7 HV for FeNiCrAl_0.7Cu_0.3Si_0.1, 577.3 ± 24.5 HV for FeNiCrAl_0.7Cu_0.3Si_0.3, and 863.2 ± 23.5 HV for FeNiCrAl_0.7Cu_0.3Si_0.5. The average friction coefficients are 0.571, 0.551, 0.524, and 0.468, respectively. The wear mass decreases from 1.31 mg in the FeNiCrAl_0.7Cu_0.3 alloy to 1.28 mg, 1.11 mg, and 0.78 mg in the FeNiCrAl_0.7Cu_0.3Si_0.1, FeNiCrAl_0.7Cu_0.3Si_0.3, and FeNiCrAl_0.7Cu_0.3Si_0.5 samples, respectively. These trends are consistent with the increase in microhardness, supporting the inverse relationship between hardness and wear. As the silicon content increases, the dominant wear mechanism changes from abrasive wear to adhesive wear, with the high-silicon alloy exhibiting lamellar debris on the worn surface. These findings confirm that silicon addition enhances microstructural refinement, mechanical strength, and wear resistance of the alloy system. Full article

In this work, arc ion plating (AIP) was employed to deposit AlCrMoN coatings on cemented carbide substrates, and the effects of substrate bias voltages (−80 V, −100 V, −120 V, and −140 V) on the microstructures, mechanical properties, and tribological behaviors of the coatings were investigated. The results showed that all AlCrMoN coatings exhibited a single-phase face-centered cubic (FCC) structure with columnar crystal growth and excellent adhesion to the substrate. As the negative bias voltage increased, the grain size of the coatings first decreased and then increased, while the hardness and elastic modulus showed a trend of first increasing and then decreasing, with the maximum hardness reaching 36.2 ± 1.33 GPa. Room-temperature ball-on-disk wear tests revealed that all four coatings demonstrated favorable wear resistance. The coating deposited at −100 V exhibited the lowest average friction coefficient of 0.47 ± 0.02 and wear rate ((3.27 ± 0.10) × 10⁻⁸ mm³/(N∙m)), featuring a smooth wear track with minimal oxide debris. During the steady-state wear stage, the dominant wear mechanisms of the AlCrMoN coatings were identified as oxidative wear combined with abrasive wear. Full article

This research delves into the corrosion resistance and wear behavior of Ni60-based composite coatings strengthened by TiC and NbC particles, which are produced by laser cladding. Three distinct coatings were prepared: S1 (Ni60 + 20%TiC), S2 (Ni60 + 10%TiC + 10%NbC), and S3 (Ni60 + 20%NbC). Microstructural characterization revealed that the addition of TiC and NbC altered phase composition, inducing lattice distortion and promoting the formation of carbides such as Cr₇C₃, Ni₃C, and Nb₂C. The S2 coating exhibited the highest average microhardness (1045 HV) due to synergistic grain refinement and homogeneous carbide dispersion. Wear resistance followed the order S2 > S3 > S1, attributed to the optimized balance of hard-phase distribution and reduced abrasive wear. Electrochemical tests in 3.5 wt% NaCl solution demonstrated superior corrosion resistance for S3, characterized by the lowest corrosion current density (1.732 × 10⁻⁶ A/cm²) and a stable passivation film, facilitated by NbC-induced oxide formation. While S2 achieved peak mechanical performance, S3 excelled in corrosion resistance, highlighting the trade-off between carbide reinforcement and electrochemical stability. This work underscores the potential of tailoring dual-carbide systems in Ni60 coatings to enhance durability in harsh environments. Full article

Valve leakage mainly comes from worn sealing surfaces caused by abrasive particles. This study uses plasma beam spraying to create Fe55 alloy coatings with CeO₂ and TiN added to improve microstructure and wear resistance. Five coatings were prepared: Fe55 with 0.02% CeO₂ (FC2), 0.04% CeO₂ (FC4), 1% TiN (FT1), 2% TiN (FT2), and 2% TiN/0.02% CeO₂ (FC2T2). These coatings were tested for wear and erosion using wet sand and slurry experiments. Results showed that FC2T2 had the most uniform microstructure with fully equiaxed grains (20.32 μm size) and no columnar grains. This was due to CeO₂ and TiN co-working effect: CeO₂ was adsorbed onto TiN surfaces, reducing TiN decomposition and acting as nucleation sites. The FC2T2 coating also showed the highest hardness uniformity (no large changes with depth) and the lowest surface roughness after wear (41% lower than pure Fe55). In wear tests, FC2T2’s Cr₇C₃ hard phases blocked abrasive cutting, while the γ-Fe matrix prevented Cr₇C₃ from breaking off. Erosion tests confirmed FC2T2’s superior performance, as its uniform structure limited deep grooves. Adding both CeO₂ and TiN improved wear resistance by providing a balanced microstructure, reducing leakage risks in valve sealing surfaces. Full article

In recent years, the field of bionic engineering has advanced at a remarkable pace. Numerous engineering challenges have been addressed through inspiration drawn from biological organisms in nature. In this paper, laser cladding was employed to fabricate a bionic unit inspired by the radial ribs of the bivalve shell surface morphology on 20CrMnTi steel, with the aim of enhancing its wear performance. The metallic powder used in the experiments was prepared by blending Ni60 alloy powder with tungsten carbide (WC) in a predetermined ratio. The WC content was maintained within a mass percentage range of 15% to 60% in the composite powder system. The microstructure and properties of the bionic unit were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and a hardness tester, while its dry sliding wear resistance was evaluated using a block-on-ring tribometer. The influence of the WC content on the microstructure, hardness, surface roughness, and wear performance of the bionic unit was investigated. The experimental results revealed that the bionic unit exhibited a dual microstructure comprising equiaxed crystals and fine dendritic structures. The incorporation of WC induced pronounced grain refinement, while the dispersed WC particles formed effective metallurgical bonding with the Ni-substrate. A positive correlation was observed between the WC content and hardness, with peak hardness reaching 1008 HV_0.2 at 60% WC. Tribological analysis demonstrated a wear mechanism transition from dominant abrasive wear to a hybrid abrasive–adhesive wear. The wear volume of the bionic unit decreased with increasing WC content, and the extent of damage was reduced. Full article

In this paper, the wear characteristics of 20GrNi2MoV bearing steel under different working conditions were investigated by finite element simulation considering microscopic grain size and pin-on-disk friction experiments, and the wear mechanism during friction and wear was explained, along with a finite element model that took initial grain size and material organization into account to predict the process of subsurface crack initiation during friction. The results show that high-speed and large-load conditions have a significant effect on the wear characteristics of dry friction of pinned disks. The effect of high speed and load will greatly reduce the time of the grinding stage, and the friction coefficient can quickly reach a stable state; the roughness of the surface of the friction pair increases with the increase in load, but the roughness shows a tendency to first increase and then decrease with the increase in sliding speed. Martensitic phase transformation occurs in the friction subsurface, and the decrease in Mn element content is one of the causes of cracks on the subsurface of the material; with the increase in load and speed, the damage form of the sample disk material is changed from abrasive wear and adhesive wear to the mixture of three kinds of wear: abrasive wear, adhesive wear, and cracks. In addition, the simulation of crack initiation and growth agrees well with the experiment, which proves the accuracy of crack prediction. This study provides a reference for crack initiation prediction in the study of pinned disk friction vises. Full article

In the process of herringbone gear grinding, excessive grinding force leads to a large increase in grinding specific energy. A large increase in the specific grinding energy can easily lead to an increase in the transient cutting load. It leads to grinding burn, tooth surface crack and other undesirable phenomena, which ultimately affect the surface quality and service performance of the workpiece. This paper is based on the contact mechanics of workpiece materials. The number of dynamic effective abrasive particles is considered. Combined with the mechanism of grinding force, the model is developed. Based on the consideration of the wear characteristics of the grinding wheel and the structure parameters of the gear itself, the grinding force model was modified. The accuracy of grinding force model is improved by dividing the effective contact angle of grinding grains into four cases. The experimental results show that the normal grinding force error reaches 10.73% and the tangential grinding force error reaches 10.34%. The model reveals the grinding mechanism, optimizes grinding parameters and improves grinding efficiency. It provides a new way for high-precision machining of aerospace precision herringbone gear. Full article