Optimization and Nanoreinforcements of Lubricant Concentration for Steel Sheet Forming Process

In metal-mechanic industry, lubricants are applied to improve products’ quality and tools useful life, while reducing friction and wear, also removing the generated heat during the material processing. Tribological evaluations are performed varying the water content of two widely used lubricants in automotive metal-forming operations. Evaluations are first performed to determine the optimal lubricant dilutions, followed by reinforcement of 2D-nanostructures of hexagonal Boron Nitride (h-BN). Tribological characterization under extreme pressures (EP) are performed with a four-ball tribometer according to the Institute for Sustainable Technologies –National Research Institute (ITeE-PIB) Polish method under scuffing conditions. The optimized concentrations are determined for Ecodraw and Montgomery lubricants, representing a 28% and 3% improvement in pressure loss limit at 1:8 and 1:6 concentrations, respectively. Block-on-ring tribotest is used to determine the coefficient of friction (COF) of the optimized lubricant dilutions and h-BN nanolubricants, which represent ~10% improvement. These results could be attributed to diverse factors such as a layering mechanism of the 2D nanostructures, soft van der Waals forces between 2D h-BN layers, and the deposition of h-BN on the worn surface, decreasing the shearing stress and COF. Finally, thermal conductivity evaluations showed an enhancement by 30% and 15% with addition of h-BN, demonstrating the potential of 2D nanostructures for improving the efficiency on antiwear and thermal transport.

Tribological Characterization of the Heat-Assisted Single Point Incremental Forming Process Applied to the Ti6Al4V Alloy with the Definition of An Adhesion Parameter for the Tool Surface

Heat-assisted single point incremental forming or HA-SPIF has a great potential for producing one-piece batches of hard-to-form materials such as Ti6Al4V alloy for medical and aeronautical applications. One of the limitations of the process is the difficulty in achieving a reasonable surface finish, which makes essential the characterization of the tribological process in the tool–sheet contact. In fact, not much work can be found at this point in literature. In this research, a novel procedure for evaluating the adhesion on the tool surface is proposed and the influence of the temperature is determined. The surface finish of parts is analyzed, and the changes promoted by HA-SPIF appearing in the morphology of the external surface layer are characterized by SEM.

Tribological Characterization of Polyether Ether Ketone (PEEK) Polymers Produced by Additive Manufacturing for Hydrodynamic Bearing Application

The coating materials commonly used in hydrodynamic bearings are the so-called “Babbitt metals” or “white metals”, as defined by ASTM B23-00. Their low Young’s modulus and yield point have encouraged researchers to find new coatings to overcome these limitations. In this paper, the friction and wear of PEEK are studied in a dry sliding environment (without lubrication) using a ball-on-disk tribometer and compared to those of Babbitt metal. Furthermore, the bond strength tests between PEEK and metals/alloys are evaluated. PEEK polymer samples were obtained from cylindrical rods, manufactured by an innovative process for polymer bonding on bearing surfaces, using additive manufacturing technology. The morphologies of the degraded surfaces were examined using a high-resolution metallurgical optical microscope (OM) and a scanning electron microscope (SEM). The coefficients of friction (CoF) were obtained under the alternating ball-on-disk dry tribometer. The results of the experimental activity show that PEEK polymers have CoFs of about 0.22 and 0.16 under the 1 and 5 N applied load, respectively. The CoF and wear volume loss results are reported and compared to the reference Babbitt coating.

Processing of Al2O3-AlN Ceramics and Their Structural, Mechanical, and Tribological Characterization

The aim of this study is to present a novel, lower sintering temperature preparation, processing, structural, mechanical, and tribological testing of the AlN-Al2O3 ceramics. The precursor powder of AlN was subjected to oxidation in ambient environment at 900 °C for 3, 10, and 20 h, respectively. These oxidized powders were characterized by SEM and XRD to reveal their morphology, phase, and crystal structure. The SEM results showed coarse powder particles and the presence of aluminum oxide (Al2O3) phase at the surface of aluminum nitride (AlN). The XRD analysis has shown increasing aluminum-oxy-nitride conversion of aluminum nitride as the holding time of oxidation increased. The highest percentage of conversion of AlN powder to AlN-Al2O3 was observed after 10 h. Simultaneously the powders were compacted and sintered using the hot isostatic pressing (HIP) under inert environment (N2 gas) at 1700 °C, 20 MPa for 5 h. This led to the compaction and increase in density of the final samples. Mechanical tests, such as bending test and tribology tests, were carried out on the samples. The mechanical properties of the samples were observed to improve in the oxidized samples compared to the precursor AlN. Moreover, applying longer oxidation time, the mechanical properties of the sintered samples enhanced significantly. Optimum qualitative (microstructure, oxide percentage) and quantitative (tribology, hardness, and bending tests) properties were observed in samples with 10-h oxidation time.

Synthesis and Tribological Characterization of Ti3SiC2/ZnO Composites

Dense Ti3SiC2/ZnO composites were sintered at different temperatures by spark plasma sintering (SPS). The effects of sintering temperature on composition and mechanical properties of Ti3SiC2/ZnO composites were studied. The tribological behaviors of Ti3SiC2/ZnO composites/Inconel 718 alloy tribo-pairs at elevated temperature from 25 °C to 800 °C were discussed. The experimental results showed that the initial decomposition temperature of the Ti3SiC2/ZnO composite was 1150 °C, and Ti3SiC2 decomposed into TiC. When the decomposition temperature was higher than 1150 °C, the compositions of the Ti3SiC2/ZnO composites were Ti3SiC2, ZnO, and TiC. It was found that Ti3SiC2/ZnO composites had better self-lubricating performance than Ti3SiC2 at elevated temperature from 600 °C to 800 °C, which was owing to material transfers of tribo-pairs and sheared oxides generated by tribo-oxidation reactions.