Fused filament fabrication is a rapidly growing 3D printing technique with the ability to produce functional components with complex shapes. The mechanical characteristics of 3D-printed parts are significantly influenced by various process parameters such as layer thickness, infill density, and nozzle temperature, which can influence part's parameters in conflicting ways. This research focuses on identifying the optimum settings for fused filament fabrication of acrylonitrile butadiene styrene. Specifically, the dimensional deviations, mechanical and abrasive wear properties of printed specimens are investigated. Experiments were designed using the Taguchi method with an L9 orthogonal array, to vary the three factors systematically. The results were analysed using analysis of variance, the Taguchi signal-to-noise ratio, and the regression analysis, with multi-response optimisation performed via desirability function analysis. The optimal balance of all three properties was achieved with infill density = 23%, layer thickness = 0.25 mm, and nozzle temperature = 240°C. This work provides a systematic, statistically validated method for multi-criteria optimisation in fused filament fabrication, offering practical guidance for producing acrylonitrile butadiene styrene components that meet multiple performance requirements simultaneously.

This experimental study investigates the critical role and impact of additive concentration in enhancing the tribological performance of castor oil as a biolubricant for agricultural tractor engines. Friction and wear are major contributors to reduced engine efficiency, highlighting the need for effective lubrication strategies. While biolubricants like castor oil offer environmental benefits, they often require additives to achieve optimal performance. However, the concentration of these additives is crucial, as an imbalance can negatively impact the lubrication system, leading to a higher coefficient of friction, increased wear, and reduced engine efficiency and lifespan. This study examines the effects of varying concentrations of a mixture of propyl gallate (PG) and ionic liquid (IL) additives on the tribological performance of castor oil. The tribological behaviour of lubricated top compression piston ring and cylinder liner samples was evaluated under simulated engine conditions using a Bruker UMT Tribolab test rig, in accordance with the ASTM G181 standard. The experimental results revealed an influence of additive concentration on the coefficient of friction and wear behaviour. This emphasises the importance of optimising additive formulations to minimise engine wear and friction. Notably, a 0.5% volume concentration of the additive mixture led to a remarkable 34.8% reduction in the average coefficient of friction (COF) and a lower wear rate.

Mechanical components undergo various wear mechanisms during operation, leading to the development of different failure modes on their surface. Identifying the different types of failure modes is essential to understand the contributing conditions to component failure. However, the identification process heavily relies on qualitative assessment of the worn surfaces by human experts, which is time-consuming, demands a high level of specialization, and is inevitably subjective. In this context, assessing three-dimensional (3D) worn topography can improve the objectiveness of identifying the surface failure modes. This study focuses on classifying indentation, grooving, pitting, and adhesive failure modes using 3D topography metrics. Historical datasets of worn topographies are considered, including ball cratering, dry sand rubber wheel, seawater corrosion, and back-to-back gear tests. An original framework, combining topography measurement and metrics with an artificial neural network, is developed for classifying these samples. Topography metrics of surface motion orientation (Smo) and surface stratification ratio (Ssr) are employed to facilitate the classification task. Smo describes how the damage is oriented towards the motion direction, while Ssr quantifies the ratio between peaks and valleys of the worn topography. When combined, they reveal a unique morphological space SmoxSsr, with improved physical interpretability, where different surface failure modes can be located. These metrics (Smo and Ssr) serve as input features of an artificial neural network designed for the automated classification of surface failure modes. When applied to the historical datasets, the developed network achieved an overall accuracy of 94% in classifying the investigated failure modes. The proposed framework offers an effective and objective solution for identifying surface failure modes in metal contacts.

This study evaluates the tribological properties of DIN 1.2740 hot tool steel against Super Cr13 martensitic stainless steel at 700 °C. The results show that the coefficient of friction (COF) ranged from 0.15 to 0.63, indicating moderate frictional interaction. The wear rate of DIN 1.2740 was observed to be low, suggesting good resistance to wear at high temperatures. The complex surface oxide layer that formed on the pin's top surface, significantly reducing the COF and acting as a solid lubricant at elevated temperatures. The oxide layer was also fragile and unable to withstand the high sliding velocities and high loads. The steel exhibited a high surface roughness when subjected to increasing normal loads and increasing sliding velocities.

The formation of a tribological layer (i.e., tribolayer) affects friction and wear behavior during sliding. The mechanisms involved can be better understood by the characterization of this layer. The wear corrosion behavior of Ti-6Al-4V was studied using a reciprocating ball-on-flat tribometer at a frequency of 1 Hz and under normal loads of 1 N, 5 N, and 15 N against an alumina ball for 3600 cycles of sliding in a phosphate buffer saline (PBS) solution. Scanning Electron Microscopy (SEM) images, along with EDS analysis showed a greater coverage of a tribolayer under a normal load of 15 N. Transmission electron microscopy (TEM) studies indicated that a tribolayer with thickness up to 1000 nm, consisting of nanograins with diameters of less than 10 nm, formed on the deformed wear surface of Ti-6Al-4V under a normal load of 15 N. This protected tribolayer, under normal loads of 5 N and 15 N, resulted in a decrease of 40% in the coefficient of friction and a 15–20% reduction in the specific tribocorrosion rate compared with that at the lower applied load.

Knowledge of wear and associated damage mechanism that is prevalent during abrasive wear conditions using NbC-based cermets is lacking. In the current investigation, the abrasive wear response and associated damage mechanisms of cermets due to characteristics effect of grit particles such as size and hardness have been explored. The present study evaluates the abrasive wear response of NbC-12Ni-10Mo2C (NbC-Ni) cermet during two-body abrasive wear, which was experimentally simulated by a pin abrasion tester following the ASTM G132 standard. The WC-Co cemented carbide (WC-15.6Co) with similar hardness was used as a reference material in this study for a comprehensive comparison of materials. The investigated test parameters included different applied loads (4–16 N) and abrasive particle sizes (22–200 μm) for a 30 m sliding distance at 0.15 m/s sliding velocity. Silicon carbide (SiC) and aluminium oxide (Al2O3) were used as abrasive counter bodies. Test results clearly show the particle size effect and the critical abrasive particle size (CPS) for the cermet lies between 82 μm and 125 μm for both abrasives (SiC, Al2O3). It is noticed that the wear rate shows three different trends as the particle size increases, initial increase then a steady state during critical particle size and becomes unpredictable. This effect reflects the transition of wear micro-mechanisms dominated from binder removal (below CPS) to fracture and fragmentations (beyond CPS). The wear mode transition map from plastic grooving to fracture-dominated failure (fragmentation and granular cracks) was created by correlating factors such as the severity of contact and specific wear rate with microscopic observations. The wear produced by SiC abrasives was about an order of magnitude higher (≈18×) than with Al2O3 abrasives. In addition, the material comparison highlight that the abrasive wear rate of NbC-Ni cermet was about 37–86% (SiC) to 66–83% (Al2O3) higher than for the WC-Co cemented carbide, despite both cermets having similar micro-hardness. In addition, the present study illustrates that the abrasion of cermets is not only related to mechanical properties such as hardness and fracture toughness but is inherently related to composite chemical properties such as wettability and interfacial strength. This work provides new insight into the wear response of NbC-Ni cermets and WC-Co cemented carbides regarding different abrasive counterfaces, abrasive particle sizes and transition of abrasive wear mechanisms.

Polyamide 11 (PA11) and copolyester (TPC-E) were compounded through melt extrusion with low levels (below 10%) of expanded graphite (EG), aiming at the manufacturing of a thermally and electrically conductive composite resistant to friction and with acceptable mechanical properties. Thermal characterisation showed that the EG presence had no influence on the onset degradation temperature or melting temperature. While the specific density of the produced composite materials increased linearly with increasing levels of EG, the tensile modulus and flexural modulus showed a significant increase already at the introduction of 1 wt% EG. However, the elongation at break decreased significantly for higher loadings, which is typical for composite materials. We observed the increase in the dielectric and thermal conductivity, and the dissipated power displayed a much larger increase where high frequencies (e.g., 10 GHz) were taken into account. The tribological results showed significant changes at 4 wt% for the PA11 composite and 6 wt% for the TPC-E composite. Morphological analysis of the wear surfaces indicated that the main wear mechanism changed from abrasive wear to adhesive wear, which contributes to the enhanced wear resistance of the developed materials. Overall, we manufactured new composite materials with enhanced dielectric properties and superior wear resistance while maintaining good processability, specifically upon using 4–6 wt% of EG.

The investigation in this article focuses on the rolling resistance torque and thermal inlet shear factor in tapered roller bearings (TRBs) through systematic experiments using a modular test setup. TRBs typically operate under Elastohydrodynamic Lubrication (EHL) conditions. At sufficiently high speeds, the majority of rolling friction is due to a significant shift of the pressure centre in the EHL contact. While at lower speeds, sliding friction in the roller-rib contact becomes dominant, which operates under mixed lubrication conditions. Limited literature exists on the impact of inlet shear heating on effective lubricant temperature ((Formula presented.)) and rolling friction in TRBs. To fill this gap, experimental measurements of the total frictional torque under axial loading at different speeds and oil temperatures are performed. With existing models for different friction contributions described in the literature, the rolling resistance due to EHL has been determined for various operating conditions. The effects of dimension-less speed (U), material (G), and load (W) parameters have also been investigated. Under fully flooded conditions, it was observed that the influence of material (G) and load (W) parameters on rolling friction is minor, while the impact of velocity (U) is significant. In the context of rolling resistance, the heating due to shear of the lubricant in the inlet zone plays a significant role. For higher rotational velocities, the estimated rotational torque reduction resulting from inlet shear heating was found to be approximately 6–8%.

The present study has developed new insights into the wear transition mode of cermets and provides a better understanding of the role of abrasive characteristics in three-body abrasive wear. Two sintered and fully densified cermets, NbC–Ni (NbC–12Ni–10Mo2C) and WC-Co (WC-9.5Co) with similar micro-hardness (HV30 ≈ 13.5 GPa) were selected in this study. The abrasion response of cermets against different abrasive characteristics namely size (67–245 μm), hardness (silica, alumina and SiC), and shape (round and angular) was experimentally investigated according to the ASTM G65 standard. The test results showed that the specific wear rate (SWR) of the cermets increased significantly with increasing abrasive size and hardness. The size effect shows that the dominant wear micro-mechanisms shift from binder removal (rolling) to mixed binder-carbide extrusion (sliding) as the abrasives particle size changes from smaller (67 μm) to larger (245 μm). The hardness ratio between the abrasives and cermets (Ha/Hs) highlights that silica and alumina abrasives provide mild wear (Ha/Hs < 1.5), while SiC abrasives cause severe wear (Ha/Hs > 1.5). Both cermets exhibited similar SWR during mild wear, but NbC–Ni showed 7 times higher SWR than WC-Co during severe wear. The abrasives shape effect does not show a significant difference on the wear rate of the cermets.

TiB2+TiB coatings were formed on Ti-6Al-4V through a molten-salt diffusional process at temperatures of 850 degrees C and 900 degrees C for 16 h. The thickness of the TiB layer increased by about two times at the higher process temperature, while the thickness of the TiB2 layer remained constant. Tribocorrosion rate of Ti-6Al-4V and the coated samples was evaluated in a reciprocating sliding under a normal load of 15 N in a phosphate buffer saline (PBS) solution for 3600-36000 cycles against an alumina ball. The results showed that the tribocorrosion rate of the borided samples decreased up to 56 times compared with Ti-6Al-4V after 36000 cycles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies showed the presence of oxide-rich patches on the wear surface of Ti-6Al-4V with a thickness of up to 1 mu m. TEM and atomic force microscopy (AFM) images also revealed the presence of a tribofilm with a thickness of up to 200 nm on the surface of the boride coating. In addition, X-ray photoelectron spectroscopy (XPS) analysis confirmed the tribofilm formed on the wear surface of coated samples contained B2O3/H3BO3 compound, resulting in a more stable fluctuation in coefficient of friction and open circuit potential during sliding. The SEM images of the alumina wear surface showed cracks and titanium transfer layers in contact with the borided layers and Ti-6Al-4V, respectively.