Search Results (882)

In this paper, the different effects of laser shock peening (LSP) and laser shock peening without coating (LSPwC) on the morphology, microhardness and fretting-wear behavior of DD6 Ni-based single-crystal superalloy are investigated. The results show that the surface roughness of DD6 decreases slightly after LSP, while it increases after LSPwC due to surface remelting. Shock wave strengthening during LSP and LSPwC results in plastic deformation of the surface layer of DD6 samples. However, besides work hardening from shock wave, dispersion strengthening of oxide particles also occurs during LSPwC. Therefore, after LSPwC, the microhardness of the DD6 surface layer increases by 38.8%, higher than the increase of 27.7% after LSP. The fretting wear resistance of DD6 increases by about 42.8% and 58% after LSP and LSPwC, respectively. The surface roughness only affects the friction coefficient at the initial stage of fretting wear. The hardness increase caused by work hardening and the dispersion strengthening of surface oxides after laser strengthening is the key to the improvement of fretting wear resistance. The main wear mechanisms of untreated and LSP sample are oxidation wear, abrasive wear and adhesive wear, while the main wear mechanisms of LSPwC sample are oxidation wear and adhesive wear. Full article

This study investigates the interplay between infill structure and surface texture in Fused Deposition Modeling (FDM)-printed polymer specimens and their combined influence on tribological and mechanical performance. Unlike previous works that focus on single-variable analysis, this work offers a comparative evaluation of Shore D hardness and coefficient of friction (COF) for PLA and Iglidur materials, incorporating diverse infill patterns. The results reveal that specific combinations (e.g., grid infill with 90% density) optimize hardness and minimize friction, offering practical insights for design optimization in functional parts. Our aim is to provide design insights for enhanced wear resistance and hardness through tailored structural configurations. Carbon Fiber-reinforced PLA (PLA CF), aramid fiber-reinforced Acrylonitrile Styrene Acrylate (Kevlar), and Iglidur I180-BL tribofilament. Disc specimens were fabricated with gyroid infill densities ranging from 10% to 100%. Experimental methodologies included Ball-on-Disc tests conducted under dry sliding conditions (5 N normal load, 150 mm/s sliding speed) to assess friction and wear characteristics. These tribological evaluations were complemented by profilometric and microscopic analyses and Shore D hardness testing. The results show that Iglidur I180-BL achieved the lowest friction coefficients (0.141–0.190) and negligible wear, while PLA specimens with 90% infill demonstrated a polishing-type wear with minimal material loss and a friction coefficient (COF) of ~0.108. In contrast, PLA CF and Kevlar exhibited higher wear depths (up to 154 µm for Kevlar) and abrasive mechanisms due to fiber detachment. Shore hardness values increased with infill density, with PLA reaching a maximum of 82.7 Shore D. These findings highlight the critical interplay between infill architecture and surface patterning and offer actionable guidelines for the functional design of durable FDM components in load-bearing or sliding applications. Full article

This article presents the results of the tribological performance of 20MnCr5 (1.7147) tool steel countersamples produced by Direct Metal Laser Sintering (DMLS), as a potential material for inserts or working layers of sheet metal forming tools. Tribological tests were performed using a roller-block tribotester. The samples were sheet metals made of materials with significantly different properties: Inconel 625, titanium-stabilised stainless steel 321, EN AW-6061 T0 aluminium alloy, and pure copper. The samples and countersamples were analysed in terms of their wear resistance, coefficient of friction (COF), changes in friction force during testing, and surface morphology after tribological contact under dry friction conditions. The tests were performed on DMLSed countersamples in the as-received state. The largest gain of countersample mass was observed for the 20MnCr5/EN AW-6061 T0 friction pair. The sample mass loss in this combination was also the largest, amounting to 19.96% of the initial mass. On the other hand, in the 20MnCr5/Inconel 625 friction pair, no significant changes in the mass of materials were recorded. For the Inconel 625 sample, a mass loss of 0.04% was observed. The basic wear mechanism of the samples was identified as abrasive wear. The highest friction forces were observed in the 20MnCr5/Cu friction pair (COF = 0.913) and 20MnCr5/EN AW-6061 T0 friction pair (COF = 1.234). The other two samples (Inconel 625, 321 steel) showed a very stable value of the friction force during the roller-block test resulting in a COF between 0.194 and 0.213. Based on the changes in friction force, COFs, and mass changes in friction pair components during wear tests, it can be concluded that potential tools in the form of inserts or working layers manufactured using 3D printing technology, the DMLS method, without additional surface treatment can be successfully used for forming sheets of 321 steel and Inconel 625. Full article

WS₂ coating, as a solid lubricating material, plays a significant role in the lubrication of rotating components in spacecraft. During the launch process, however, spacecraft are exposed to high-temperature and humid atmospheric environments, which can lead to oxidative failure in the coating, thereby limiting its engineering applications. By doping with B elements, B/WS₂ was successfully prepared as a composite coating. The results demonstrate that the fabricated coating exhibits excellent high-temperature tribological performance in atmospheric environments. The mechanism through which B doping improves the high-temperature friction and wear properties of the WS₂ composite coating was revealed through high-temperature friction and wear tests. With the incorporation of B elements, the average friction coefficient of the coating was 0.071, and the wear rate was 7.63 × 10⁻⁷ mm³·N⁻¹·m⁻¹, with the wear mechanisms identified as abrasive wear and spalling. Due to high-temperature oxidation, thermal decomposition effects, and the formation of WB₄ during sputtering, the wear resistance and anti-plastic deformation capability of the coating were further improved. Compared to room-temperature test conditions, the B/WS₂ composite coating at different high temperatures exhibited superior friction coefficients and wear rates. Notably, at 150 °C, the average friction coefficient was as low as 0.015, and the wear forms were abrasive wear and adhesive wear. Full article

Tribological processes in extreme environments pose serious material challenges, requiring coatings that resist both wear and corrosion. This review summarizes recent advances in protective coatings engineered for extreme environments such as high temperatures, chemically aggressive media, and high-pressure and abrasive domains, as well as cryogenic and space applications. A comprehensive overview of promising coating materials is provided, including ceramic-based coatings, metallic and alloy coatings, and polymer and composite systems, as well as nanostructured and multilayered architectures. These materials are deployed using advanced coating technologies such as thermal spraying (plasma spray, high-velocity oxygen fuel (HVOF), and cold spray), chemical and physical vapor deposition (CVD and PVD), electrochemical methods (electrodeposition), additive manufacturing, and in situ coating approaches. Key degradation mechanisms such as adhesive and abrasive wear, oxidation, hot corrosion, stress corrosion cracking, and tribocorrosion are examined with coating performance. The review also explores application-specific needs in aerospace, marine, energy, biomedical, and mining sectors operating in aggressive physiological environments. Emerging trends in the field are highlighted, including self-healing and smart coatings, environmentally friendly coating technologies, functionally graded and nanostructured coatings, and the integration of machine learning in coating design and optimization. Finally, the review addresses broader considerations such as scalability, cost-effectiveness, long-term durability, maintenance requirements, and environmental regulations. This comprehensive analysis aims to synthesize current knowledge while identifying future directions for innovation in protective coatings for extreme environments. Full article

This study focuses on the optimization of valve assemblies in downhole rod pumping units (DRPUs), which remain the predominant artificial lift technology in oil production worldwide. The research addresses the critical issue of premature failures in DRPUs caused by leakage in valve pairs, i.e., a problem that accounts for approximately 15% of all failures, as identified in a statistical analysis of the 2022 operational data from the Uzen oilfield in Kazakhstan. The leakage is primarily attributed to the accumulation of mechanical impurities and paraffin deposits between the valve ball and seat, leading to concentrated surface wear and compromised sealing. To mitigate this issue, a novel valve assembly design was developed featuring a flow turbulizer positioned beneath the valve seat. The turbulizer generates controlled vortex motion in the fluid flow, which increases the rotational frequency of the valve ball during operation. This motion promotes more uniform wear across the contact surfaces and reduces the risk of localized degradation. The turbulizers were manufactured using additive FDM technology, and several design variants were tested in a full-scale laboratory setup simulating downhole conditions. Experimental results revealed that the most effective configuration was a spiral plate turbulizer with a 7.5 mm width, installed without axis deviation from the vertical, which achieved the highest ball rotation frequency and enhanced lapping effect between the ball and the seat. Subsequent field trials using valves with duralumin-based turbulizers demonstrated increased operational lifespans compared to standard valves, confirming the viability of the proposed solution. However, cases of abrasive wear were observed under conditions of high mechanical impurity concentration, indicating the need for more durable materials. To address this, the study recommends transitioning to 316 L stainless steel for turbulizer fabrication due to its superior tensile strength, corrosion resistance, and wear resistance. Implementing this design improvement can significantly reduce maintenance intervals, improve pump reliability, and lower operating costs in mature oilfields with high water cut and solid content. The findings of this research contribute to the broader efforts in petroleum engineering to enhance the longevity and performance of artificial lift systems through targeted mechanical design improvements and material innovation. Full article

Nickel-based superalloy Hastelloy C276 is widely used in high-performance industries due to its strength, corrosion resistance, and thermal stability. However, these same properties pose substantial challenges in machining, resulting in high tool wear, surface defects, and dimensional inaccuracies. This study investigates methods to enhance machining performance and surface quality by evaluating the tribological behavior of TiSiN/TiAlN-coated carbide inserts under six cooling and lubrication conditions: dry, MQL with coconut oil, Cryo-LN₂, Cryo-LCO₂, MQL–Cryo-LN₂, and MQL–Cryo-LCO₂. Open-slot finishing was performed at constant cutting parameters, and key indicators such as cutting zone temperature, tool wear, surface roughness, chip morphology, and microhardness were analyzed. The hybrid MQL–Cryo-LN₂ approach significantly outperformed other methods, reducing cutting zone temperature, tool wear, and surface roughness by 116.4%, 94.34%, and 76.11%, respectively, compared to dry machining. SEM and EDS analyses confirmed abrasive, oxidative, and adhesive wear as the dominant mechanisms. The MQL–Cryo-LN₂ strategy also lowered microhardness, in contrast to a 39.7% increase observed under dry conditions. These findings highlight the superior performance of hybrid MQL–Cryo-LN₂ in improving machinability, offering a promising solution for precision-driven applications. Full article

Wide-range electric submersible centrifugal pumps (ESPs) are critical for offshore oilfields but suffer from narrow high-efficiency ranges and frictional losses under dynamic reservoir conditions. This study introduces bio-inspired dimple-type non-smooth surfaces on impeller blades to enhance hydraulic performance. A combined numerical-experimental approach was employed: a 3D CFD model with the k-ω turbulence model analyzed oil–water flow (1:9 ratio) to identify optimal dimple placement, while parametric studies tested diameters (0.6–1.2 mm). Experimental validation used 3D-printed prototypes. Results revealed that dimples on the pressure surface trailing edge reduced boundary layer separation, achieving a 12.98% head gain and 8.55% efficiency improvement at 150 m³/d in simulations, with experimental tests showing an 11.5% head increase and 4.6% efficiency gain at 130 m³/d. The optimal dimple diameter (0.9 mm, 2% of blade chord) balanced performance and manufacturability, demonstrating that bio-inspired surfaces improve ESP efficiency. This work provides practical guidelines for deploying drag reduction technologies in petroleum engineering, with a future focus on wear resistance in abrasive flows. Full article

Polyimide (PI), owing to its high heat resistance and low density, is often employed as a substitute for metallic materials in high-temperature environments, such as aircraft engines, bearings, and gears. However, the relatively high friction coefficient of pure PI limits its application under harsh conditions. Therefore, this study synthesized a composite lubricant with binary fillers to improve this performance. This study employed the hydrothermal method to synthesize MoS₂/MXene composite lubricating fillers and systematically investigated the high-temperature tribological properties of PI composites reinforced with these fillers. The results demonstrated that the optimal PI composite containing 5% MoS₂/MXene exhibited a 14 °C increase in initial decomposition temperature compared to pure PI. Additionally, its thermal conductivity was enhanced by 36%, while the hardness (0.398 GPa) and elastic modulus (6.294 GPa) were elevated by 12.4% and 18.6%, respectively, relative to the pure PI. In terms of tribological behavior, all composite formulations displayed typical temperature-dependent friction characteristics. It is worth noting that MXene’s high hardness and thermal conductivity inhibited the occurrence of abrasive wear. At the same time, the substrate was strengthened, and thermal resistance was enhanced, thereby delaying the plastic deformation of the material at high temperatures. Full article

In this study, solid particle erosion tests were conducted to evaluate the resistance of AISI 4340 (EN24) and 8620 alloy steels against silicon carbide (SiC). These steels were selected due to their high hardness, yield strength (σ_y), ultimate tensile strength (σ_uts) and elongation (%), which are significant parameters, influencing wear resistance. An erosion rig based on the ASTM G76-95 standard was used to perform the testing. Tests were carried out using different impact angles, 30°, 45°, 60° and 90°, with a particle velocity of 24 ± 2 m/s. The abrasive flow rate was 0.7 ± 0.5 g/min and the temperature was between 35 °C and 40 °C. Characterization techniques such as SEM were employed to identify the chemical composition of AISI 4340 and AISI 8620 steels and optical microscopy to determine the morphology of SiC abrasive particles. In addition, the SiC particle size was between 350 and 450 µm; it was determined by the particle size distribution technique. SEM micrographs were obtained to classify the wear mechanisms, characterized by micro-cutting, micro-ploughing, grooves, pitting actions and embedded particles on the surface at 30° and 90°. The results showed that AISI 8620 steel exhibited higher erosion resistance than AISI 4340 steel. Finally, AFM was used to evaluate the roughness variations before and after erosion tests, specifically in the central zone of the wear scars at 30° and 90° for both materials. Full article

This article focuses on the possibilities of increasing the service life of tools for crushing unwanted growths. One way to increase their service life is to increase the hardness and resistance to abrasive wear of exposed surfaces of the tool, which are their face and back. At the same time, however, care must be taken to ensure that the shape and weight of the tool is not altered after the additive has been hardfaced on. Thus, the tool was first modified by removing the material by milling from the face and back. Subsequently, two surfacing materials, namely UTP 690 and OK WearTrode 55, were chosen and hardfaced by welding onto the pre-prepared surfaces. After hardfacing by welding, the tools were ground to their original shape and their weight was measured. Subsequently, the tool was sawn, and specimens were created for Rockwell hardness evaluation, material microstructure and for abrasive wear resistance testing as per ASTM G133-95. The OK WearTrode 55 electrode is a hardfacing electrode that produces weld metal with a high-volume fraction of fine carbides in a martensitic matrix. Better results were achieved by the UTP 690 hardfacing material. The hardness was 3.1 times higher compared to the base tool material 16MnCr5 and 1.2 times higher than the OK WearTrode 55 material. The abrasive wear resistance was 2.76 times higher compared to 16MnCr5, and 1.14 times higher compared to the OK WearTrode 55 material. The choice of a suitable pre-treatment for the tool and the selection and application of such additional material, which with its complex properties better resists the effects of the working environment, is a prerequisite for increasing the service life of tools working in forestry. 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

Metallic glasses (MGs) with excellent mechanical properties have significant applications in frontier technological fields such as medical, energy and aerospace industries. Recently, MGs have been considered as ideal candidates for subzero engineering applications due to their disordered atomic structure array. However, the mechanical properties and wear behaviors of MGs at subzero temperatures have rarely been explored. In this work, the wear properties and wear mechanisms of Zr-based MG were systematically evaluated at a subzero temperature of −50 °C. Compared to the wear results at room temperature, MG in a subzero environment shows a ~60% reduction in wear rate. The main contributing factor is that MG at room temperature will easily forms a thin, brittle oxide layer at the sliding interface, which will lead to oxidation, adhesive and abrasive wear on its surface, whereas these wear behaviors do not occur in subzero conditions where only abrasive wear occurs. Meanwhile, MG at subzero temperatures has a higher elastic modulus. These properties make MG more wear-resistant in subzero environments. The current study will provide new perspectives on the wear mechanisms and subsurface deformation of MG in subzero environments and valuable insights into the use of MG in subzero engineering applications, such as deep space and polar exploration. Full article

This study investigates the tribo-corrosion behavior of Ti6Al4V biomedical alloy, when sliding against fused filament fabrication (FFF) 3D-printed polyether ether ketone (PEEK) pins in a phosphate-buffered saline (PBS) solution. This research aims to evaluate wear mechanisms and electrochemical responses under simulated physiological conditions, providing critical insights for enhancing the durability and performance of biomedical implants. Potentiodynamic polarization tests demonstrate that the Ti6Al4V alloy possesses excellent corrosion resistance, which is further enhanced under sliding conditions compared to the test without sliding. When tested against 3D-printed PEEK, the alloy exhibits a mixed wear mechanism characterized by both abrasive and adhesive wear. Open-circuit potential (OCP) measurement of Ti6Al4V demonstrates the alloy’s superior electrochemical stability, indicating high corrosion resistance and a favorable coefficient of friction. These findings highlight the potential of 3D-printed PEEK as a viable alternative for biomedical applications, offering rapid patient-specific prototyping, tunable mechanical properties, and improved surface adaptability compared to conventional materials. Full article

A plasma electrolytic oxidation (PEO) coating was produced on 6061 aluminum alloy within a silicate-containing electrolyte using a bipolar pulsed power supply. The impact of K₂ZrF₆ addition on the wear resistance of the coating was investigated. The phase composition, surface morphology, and elemental distribution of the coatings were assessed by means of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). Experimental data revealed that the growth rate of the coating increased by 37.3% compared to that without K₂ZrF₆; the addition of K₂ZrF₆ favored the formation of mullite and enhanced the coating densification; it also improved the breakdown voltage of the coating, which increased by 46.0% compared to that without K₂ZrF₆; and it also demonstrated excellent abrasion resistance, with a reduction of 41.8% in the weight of the abrasion. Full article