In recent years, additive manufacturing, especially 3D printing, has been gaining more space in the production of parts and components in various industries. Among the polymer materials, polylactic acid (PLA) stands out due to its renewable sources, such as corn starch or sugar cane. This study focused on the evaluation of the coefficient of friction (CoF) and wear resistance of pins of pure PLA, pure thermoplastic polyurethane (TPU), and bronze‐filled PLA (BRO), all produced by fused deposition modeling (FDM). The pins were rubbed against a SAE 1020 steel counterpart in a pin‐on‐disc apparatus. The wear tests also included combinations of BRO/PLA and TPU/PLA (with a pattern on the surface), combined at three different percentages (25%, 50%, and 75%). Pure BRO showed the lowest wear rate ( K ≈0.9 × 10 ⁻⁵ mm ³ /N m), while pure PLA exhibited the lowest CoF among the pins ( μ ≈0.24) but the highest wear ( K ≈16.7 × 10 ⁻⁴ mm ³ /N m). The combination of 75% of BRO with 25% of PLA demonstrated a favorable balance between friction and wear, with a wear resistance close to BRO ( K ≈0.8 × 10 ⁻⁵ mm ³ /N m) and a CoF similar to pure PLA ( μ ≈0.28). The paper extensively discusses the wear mechanisms observed on the worn surfaces, as well as the tribofilm formed on the steel disc counterpart.

The growing demand for sustainable, high-performance composite materials has increased the interest in natural fibers as reinforcements for brake friction materials (BFMs). Silk and Grewia optiva fibers, in particular, have emerged as promising candidates for BFMs due to their good mechanical properties, biodegradability, and availability. To evaluate their potential, friction materials were formulated with 6% Grewia (GF), 6% silk (SF), and a hybrid formulation containing 3% of both fibers (SGF), alongside a reference material reinforced with 6% aramid fiber (AF). These composites were then tested on a braking tribometer using an extended SAE J2522 procedure to assess their performance. The AF formulation showed slightly better wear resistance and the GF formulation showed inferior performance during high-temperature cycles, whereas SF and SGF performed close to the reference formulation (AF) in these sections. In terms of friction stability, SF matched the AF formulation, while GF demonstrated significantly poorer stability. The first high-temperature exposure of the BFMs (Fade 1) served as a critical thermal settlement phase, after which they demonstrated both improved friction stability and repeatable performance characteristics. Finally, this study demonstrates that silk fiber represents a viable, sustainable alternative to aramid in BFMs, exhibiting comparable performance in terms of friction stability and thermal resistance.

The transition toward sustainable industrial practices has led to the development of eco-friendly vegetable oils (biolubricants) as alternatives to traditional petroleum-based lubricants. However, vegetable oils are inherently susceptible to oxidative and thermal degradation at high temperatures. To overcome this, chemical modification of the pure oil is commonly employed, which not only enhances thermo-oxidative stability but also improves intrinsic lubricity. To further boost lubrication under severe conditions, dispersing solid nanoparticles into the oil has emerged as a highly effective strategy. Therefore, this study investigates the scuffing behavior of MoS₂-based nanofluids formulated with castor oil (CO) and a chemically modified vegetable oil (aminolyzed castor oil—ACO). Scuffing tests were performed in a block-on-ring tribometer. Nanofluids containing 0.10, 0.15, and 0.20 wt.% MoS₂ were compared to their additive-free base oils. Friction force evolution was quantitatively analyzed to identify characteristic scuffing phases. Results demonstrated that MoS₂ increases severe scuffing resistance, with this resistance strongly depending on the base oil and nanoparticle concentration. Among the formulations, ACO with 0.10 wt.% MoS₂ exhibited the best performance, increasing the Weibull characteristic life (α) by approximately 36.7% compared with additive-free ACO. Furthermore, the nanofluids exhibited a more stable friction response during severe scuffing, in contrast to the pronounced friction instabilities observed with the additive-free base oils. SEM/EDS analyses revealed molybdenum oxides on worn surfaces, indicating tribochemical reactions and protective tribofilm formation activated by high temperature. Overall, chemical modification of the base oil (i.e., ACO) enhances the beneficial effects of MoS₂ nanoparticles, highlighting ACO-based nanofluids as promising lubricants for severe tribological applications.

Global demand for manufacturing processes aligned with cleaner practices has increased interest in vegetable-based oils (biolubricants) as eco-friendly alternatives to petroleum-based oils. In this context, a novel vegetable emulsion was proposed as a cutting fluid in a turning process. This emulsion was formulated with 1 wt% aminolyzed castor oil (ACO) and 99 wt% water. ASTM A182 F55 super duplex stainless steel was selected as the workpiece because of its high work-hardening rate, high ductility, and low thermal conductivity result in low machinability, opening new research opportunities in the field of machining. Three cutting conditions were used in the turning process: dry cutting (DRY), Minimum Quantity Lubrication (MQL) with a semi-synthetic emulsion (SS-MQL), and MQL with an ACO emulsion (V-MQL). The experiments were conducted using TiAlN-coated carbide cutting tools. The results of V-MQL exhibited the lowest tool wear among the cutting conditions due to the formation of a protective film promoted by the ACO emulsion, which was adsorbed on the tool’s surface. Regarding chip formation, the DRY condition produced long and tangled chips with larger saw-tooth spacing. In contrast, both MQL conditions generated shorter chips with smaller saw-tooth spacing due to the cooling effect of the emulsions. Additionally, V-MQL promoted the highest chip work hardening, followed by SS-MQL and DRY. All cutting conditions showed a suitable surface finish, especially V-MQL and SS-MQL. Under the cutting conditions used in this study, the ACO emulsion proved effective for machining ASTM A182 F55 steel, standing out as a promising alternative to conventional cutting fluids.