Cutting and forming tools operating under high load conditions often suffer from premature wear. Applying hard, wear-resistant coatings particularly multilayer coatings can significantly enhance their functional properties. In this study, three multilayered coatings were deposited on hardened M2 steel bars using arc-evaporation: (1) TiN/TiCrN/TiN, (2) TiN/TiCrN/(TiN/CrN)(10)/TiN system and (3) (Cr/CrN)(25). Mechanical (nanoindentation), tribological (cylinder on cylinder reciprocating tests) behavior of the coatings was investigated along with microimpact tests. SEM/TEM analysis of the coatings revealed dense and fine-grained columnar structure in the direction of growth. All multilayer coatings showed enhanced wear resistance compared to the TiN monolayer. The TiN/TiCrN/TiN system exhibited the highest hardness (30.6 GPa) and best wear resistance against Al2O3, with an 88 % reduction in volume loss compared to TiN. This performance is consistent with its high load-bearing capacity (H-3/E-2 = 0.107 GPa), moderate H/E (0.059) and the lowest friction coefficient (<0.2). On the other hand, the (Cr/CrN)25 coating demonstrated the best impact performance - with no chipping at 500 mN over 500 cycles and minimal damage at 1500 mN. This is attributed to its high H/E (0.074) and H-3/E-2 (0.126 GPa) ratios, along with a relatively low modulus (310 GPa), much more closely matched (E-c/E-s similar to 1.5) to the substrate than the other coatings.

A novel test method for more closely replicating the statistical, and apparently stochastic, distribution of multiple impacts that occur in solid particle erosion is to perform multiple impacts with controlled energy at different locations on the sample surface using a nanomechanical test instrument where sample stage movement between impacts enables each impact to be at a new position. In this work we have applied the new method to investigate the behaviour of hard, wear resistant PVD TiAlN and AlCrN coatings on cemented carbide, comparing their behaviour to that in cyclic micro-impact tests where the multiple impacts occur at the same position. Both coatings showed a strongly load-dependent behaviour in the statistically distributed impact test. A transition to lateral cracking with continued impact occurred more readily on AlCrN, with more extensive lateral cracking at higher load than on TiAlN. In contrast, in cyclic impact tests the TiAlN performed poorly at lower load whilst the AlCrN was resistant to lateral cracking. At high load AlCrN was more variable, with dramatic failure in some tests and no failure in others. Reasons for these differences are discussed.

This study investigates the use of duplex coatings, TiN/diamond-like-carbon (DLC), on improving the tribological performance of stainless steel 316L which is commonly used for femoral stems in total hip replacement implants. A range of substrate pre-treatment variants (nitriding and polishing) were applied to investigate the impact on the mechanical and tribological performance of the coatings. The tribological performance of plasma vapour deposition duplex coating variants was tested using a bespoke in-house fretting tribometer with an electrodynamic shaker utilising a ball-on-plate configuration. Fretting was replicated by applying micro-motion to the Ø12 Al2O3 ball relative to duplex coated SS 316L plates under a dead weight normal load. Un-polished substrates prior to the coating deposition led to improved tribological performance likely due to improve coating adhesion to the substrate surface. The hydrogenated DLC sample variants showed lower friction performance compared to hydrogen-free DLC variants most likely due to higher amounts of graphitisation.

Carbides/nitrides (MXenes) have been applied in various fields due to their unique two-dimensional structure and excellent conductivity. However, the sediments from the preparation of MXenes were often discarded without full utilization, which generates huge waste and potential environmental pollution. Here, a strategy of turning waste into treasure is proposed. Sediments from the preparation of Ti3C2Tx have been effectively recycled, and strain sensors have been fabricated based on a 25% Ti3C2Tx -Ti3AlC2/PVA composite film for human motion monitoring. The strain sensor shows a fast response with a gauge factor of 5.53 under the strain of less than 10%. We give a model to explain the operating mechanism of Ti3C2Tx-Ti3AlC2/PVA during the stretching process. The monitoring of human motions on fingers and wrists demonstrates extremely high sensitivity (response time <100 ms). Moreover, the strain sensor exhibits excellent stability. This research opens the door for the future recycling of the sediments generated during the preparation of MXenes.

This study investigates the machining characteristics of a High Entropy Alloy, CrMnFeCoNi (Cantor's Alloy), when machined with different metalworking fluids. Selective Laser Melting was used to additively manufacture the material block from powder, which was then used in a parametric study of machining responses in comparison to a reference AISI 304L stainless steel. Tool life and power consumption was monitored when unadditised and commercial metalworking fluid variants were used during the machining of both materials. The study demonstrated that it was harder to machine the high entropy alloy, likely due to the high hardness and lower thermal conductivity of the material. It was also found that the commercial metalworking fluid increased tool life compared to the unadditised fluid when machining 304L, however no difference in tool life was observed when machining with the high entropy alloy. It may be that the elemental composition of the high entropy alloy impacted the formation of a protective film that could influence tool life, as has been observed with other materials.

MXenes show great potential in energy storage due to their excellent conductivity, abundant surface groups and adjustable interlayer spacing. Amino modification is an effective strategy to improve electrochemical properties of MXene. However, the selection of amino source is still a key issue. Herein, the amino modification of Ti3C2 MXenes for high-performance supercapacitors has been investigated. The structure and electrochemical properties of Ti3C2 are modified by different amino sources, such as ethylenediamine (EDA), monoethanolamine (MEA) and hydrazine monohydrate (HM). EDA ensures Ti3C2 the largest interlayer spacing (13.96 & Aring;) and highest specific surface area (52.2 m2g- 1). In addition, there are more functional groups in EDA-modified Ti3C2 (EDATi3C2) resulted from the stronger electron-donating nature of EDA than HM and MEA. Thus, EDA-Ti3C2 exhibits the largest specific capacitance of 683 F g- 1 in 1 M H2SO4 electrolyte at 2 mV/s, and the capacitance maintains 97.3 % of the original after 10,000 cycles at 50 mV/s. As a comparison, MEA-Ti3C2 and HM-Ti3C2 show specific capacitances of 553 F g- 1 and 470 F g-1, respectively. Furthermore, the symmetric supercapacitor based on EDATi3C2 electrode achieves maximum energy density of 7.87 W h kg- 1 at power density of 600 W Kg-1, and the energy density still remains at 6.34 W h Kg- 1 even at an increased power density of 3000 W Kg-1. This study proposes a simple strategy to enhance electrochemical properties of MXene by amino modification, providing valuable insights for high-performance supercapacitors.

Surface functionality plays a pivotal role in Tribology, a discipline dedicated to examining the interactions of surfaces in relative motion. The approach, known as Tribotronics, combines Tribology and electronics, enabling active tribological components to be embedded in larger systems and networks constituting the Industrial Internet of Things. Leveraging novel technologies such as advanced sensing coatings and triboelectric nanogenerators, the sensing capability of Tribotronic systems undergoes a transformative shift from a device‐centric to a surface‐centric paradigm. This critical advancement unlocks the potential for direct interface probing and in‐situ measurement of tribological processes, marking a significant milestone in the field. This emerging trend introduces the concept of the Internet of Surfaces, a novel perspective within surface engineering. It entails the amalgamation of sensing capabilities, embedded power generation, and external analytics, creating dynamic materials in the context of Industry 4.0.

MXenes possess high metallic conductivity and excellent dispersion quality and pseudocapcitance. Their good hydrophilicity makes them particularly suitable as eco-friendly inks for printing applications. However, MXenes are prone to oxidization in aqueous dispersions, and it is very important to improve their stability. Here, the long-term storage of MXene aqueous dispersions was realized by the introduction of sodium L-ascorbate (NaAsc) as the antioxidant. The preserved MXenes exhibited very stable electrochemical properties. Even after 60-day storage, the supercapacitor with preserved MXenes as the electrode still demonstrated an excellent specific capacitance of 381.1 F/g at a scan rate of 5 mV/s and a good retention rate of 92.6% after 10,000 consecutive cyclic voltammetry measurements, which was nearly the same as that of fresh MXenes. The results indicate a facile and efficient method to realize the long-term storage of MXene aqueous dispersions for mass use in future energy storage.

Achieving macroscale structural superlubricity with two-dimensional (2D) materials under ultrahigh contact pressure in ambient condition is particularly challenging. Furthermore, the mechanisms underlying the disparate trans-scale tribological behaviors of 2D materials continue to be a subject of debate. Here, we propose a novel principle concerning pressure-induced dynamic structural evolution and tribochemical behaviors of tribolayers to broaden the macroscale structural superlubricity. For the first time, robust macroscale structural superlubricity with ultralow wear rate is realized by 2D material coating in ambient condition by sliding steel counterparts under ultrahigh contact pressure. The results reveal that macroscale structural superlubricity of 2D materials is highly dependent on the dynamic evolution of tribolayers nanostructures, as well as the adsorption and tribochemical behaviors governed by extreme pressure. These findings shed light on achieving robust macroscale structural superlubricity with 2D materials for harsh engineering conditions.

Sealing treatment provides a strategy for the long-term performance of thermal spray coatings under actual working conditions. However, common sealants are mainly limited to improving the corrosion resistance of coatings, neglecting applications in more complex environments where they are subject to simultaneous corrosion and wear. Herein, a novel organic-inorganic hybrid composite sealant, composed of self-lubricating MoS2 nanoparticles and environmentally friendly waterborne silicone modified acrylic resin (WBS-ACR), was successfully prepared in the pores and micro-defects of plasma-sprayed HEA coatings by one-step hydrothermal method. The results indicate that MoS2 nanosheets are uniformly synthesized in resin materials through precursor hydrothermal reactions. The hybrid sealants are filled densely in the micro-defects of HEA coatings with a maximum penetration depth greater than 180 mu m. The tribological and electrochemical results indicate that the hybrid sealant exhibits similar anti-wear performance, but two orders of magnitude lower corrosion currents than that of pure MoS2 sealant. In comparison to the pure resin sealant, the hybrid sealant retains its excellent corrosion resistance while increasing its wear resistance. The superior comprehensive performance of the novel organic-inorganic hybrid sealant could expand the application of thermal spray coatings into new fields.

MAX phases are intriguing materials due to their unique properties. However, each of these materials possesses its own weaknesses when subjected to service conditions. For example, while one MAX phase exhibits self-lubricating feature, it may not perform well under high load conditions. This study investigates the impact of adding chromium to Ti2AlC on microstructure and mechanical properties. Samples are prepared through ball-milling and spark plasma sintering (SPS), then analyzed using various techniques. The presence of different phases, including MAX phases (Ti2AlC and Cr2AlC), carbides (TiC and Cr7C3), and low amounts of oxides, is identified. Hardness, fractography, and wear characteristics are assessed through indentation and sliding tests. The study correlates the wear rate of each sample with experimental (H/E) and theoretical indicators (B/G), showing the production of composites with improved properties suitable for diverse applications.

High entropy alloy composites (HEACs) have recently been explored for use in industrial applications. This study investigates the impact of particle size (micro or nano) and content (5 and 10 wt

Metalworking fluids have the ability to extend cutting tool life and improve the machinability of materials. There is a need for the development of reliable machining tests which can be used to screen fluids with high confidence to allow for ranking in terms of performance. This study developed a novel methodology utilizing single-point milling to evaluate fluid performance in terms of tool wear and cutting forces across various aerospace alloys. The repeatability of the procedure was assessed and demonstrated by using standard deviation. The study showed alternative cutting fluid compositions could influence tool life performance across all the aerospace material variants. Inconel 718 was shown to be the hardest material to machine followed by Titanium Ti–5Al–5Mo–5V–3Cr and Titanium Ti–6Al–4V. However, with each material, there was a differentiation in fluid performance with up to 11% difference in average tool life between different fluids.

Diamond-like carbon coatings have previously been studied as a protective coating for fretting wear protection providing low friction and low wear. H/E ratio has been used as a metric to rank coating performance in sliding wear, but this has not been applied to gross-slip fretting. Three DLC coating systems (a-C:H, Si-a-C:H, a-C:H:W top layers) on hardened M2 tool steel were studied using a bespoke electrodynamic shaker with a 10 mm 52100 steel ball as the counterface. This work has shown that H/E ratio can be used to predict wear performance in gross-slip fretting; the highest H/E ratio a-C:H performed best with low friction and wear.

The wider availability of low-cost sensing and data acquisition technologies means that real-time sensing of tribological parameters is becoming increasingly viable. Consequently, the potential to use these technologies to monitor in-service tribological components has increased significantly. This paper presents a review of a number of state-of-the-art in sensors for measuring friction, wear and lubricant properties. It also elaborates on the use of sensor coatings as an emerging area for directly probing the tribological interface. It is concluded that sensors will find ever increasing uses in condition monitoring” applications. However, sensing and tribology is beginning to evolve towards “Tribotronics” where combining the sensing of machine elements that have conventionally been passive with computational capability, or even embedded intelligence, along with actuation can create active machine elements, optimised to operate with say minimum power loss in all situations of duty. Additionally, it is noted that by incorporating sensing and responsive capabilities, functional surfaces can also become part of a bigger connected systems particularly in association with Industry 4.0. Increased use of sensors in tribological components alongside machine learning and artificial intelligence, will also support the shift in industrial tribological analytics.

Although fretting, as a serious problem in mechanical engineering, has been recognized for at least a century, the mechanics of the problem, and the influence of fretting on component failures either through the shortening of fatigue life or through the emergence of wear has been studied since only the late 1950s. A synthetic review of the work carried out will be presented here in order to trace out the development of the knowledge acquired in the last few decades, covering the progress made and the contributions by the pioneers of the field, as well as providing an overview of recent advances and current efforts in this area.