The machining process is still a very relevant process in today’s industry, being used to produce high quality parts for multiple industry sectors The machining processes are heavily researched, with the focus on the improvement of these processes One of these process improvements was the creation and implementation of tool coatings in various machining operations These coatings improved overall process productivity and tool-life, with new coatings being developed for various machining applications TiAlN coatings are still very present in today’s industry, being used due to its incredible wear behavior at high machining speeds, high mechanical properties, having a high-thermal stability and high corrosion resistance even at high machining temperatures Novel TiAlN-based coatings doped with Ru, Mo and Ta are currently under investigation, as they show tremendous potential in terms of mechanical properties and wear behavior improvement With the improvement of deposition technology, recent research seems to focus primarily on the study of nanolayered and nanocomposite TiAlN-based coatings, as the thinner layers improve drastically these coating’s beneficial properties for machining applications In this review, the recent developments of TiAlN-based coatings are going to be presented, analyzed and their mechanical properties and cutting behavior for the turning and milling processes are compared

Characteristics and Wear Mechanisms of TiAlN-Based Coatings for Machining Applications: A Comprehensive Review

Covalent adaptable networks (CANs), which can reconfigure on-demand under photo- or thermal stimuli, have recently been pursued as an alternative to the traditional thermosetting polymers. While these materials have demonstrated excellent recyclability and reprocessability, the majority of them reported to date are based on non-renewable resources. Meanwhile, material recycling highly counts on the collection system, and any materials that inevitably escape from the collection system will eventually go to the environment, challenging nature’s ability to break down these materials. Therefore, CAN materials that possess both recyclability and degradability are highly desirable. In this work, we seek to simultaneously address the recyclability, renewability, and degradability of CAN materials. Spiro diacetal building blocks are derived from bio-based benzaldehyde and erythritol and then subjected to the curing process using bio-based epoxy soybean oil as crosslinkers, yielding fully biobased CAN materials. Owing to the dynamic and degradable features of acetal motifs, our CAN materials exhibit both good recyclability and acid degradability, and the degraded products are reusable for preparation of new CANs. In addition, by tuning the steric hindrance adjacent to the reactive phenol site, we are able to control the mechanical properties of CANs using different bio-based benzaldehydes (vanillin, ethyl vanillin, and syringaldehyde). The outcome of the current research provides a strategy for the design of recyclable and degradable bio-based CANs, which will extend the development of CANs. 

Recyclable, Degradable, and Fully Bio-Based Covalent Adaptable Polymer Networks Enabled by a Dynamic Diacetal Motif

Surface modification technologies for enhancing the tribological properties of cemented carbides: A Review

Ti-6Al-4V alloy has low thermal conductivity, poor machinability, and active chemical activity. However, it is easily bonded to tool surface in the cutting process, resulting in drastic tool wear. The friction contact state and friction behavior between the tool and machined surface can be significantly improved when adopting tool with micro texture on the surface. The tools with line texture, regular hexagonal texture, and without texture on the rake face were adopted in this study. The cutting force, tool wear morphology, and friction coefficient of different type of tools are analyzed based on dry cutting test, friction, and wear test of cemented carbide and titanium alloy. The result shows that the cutting force caused by the line-textured tool is the smallest, following by hexagonal-textured tool and no-textured tool. However, large damage would happen at the cutting edge of line-textured tool as the cutting continues, while the damage of hexagonal-textured tool is relatively light. The main cutting force and feed force of the three kinds of tools increase as cutting depth increased, while decrease with the increase of cutting speed. The wear morphology of textured tool is smoother than that of no-textured tool, due to the micro texture can contain debris and reduce friction coefficient. A cutting force equation is established by ridge regression method based on actual cutting data, which provides a new idea for monitoring the tool during cutting process.

Effect of surface line/regular hexagonal texture on tribological performance of cemented carbide tool for machining Ti-6Al-4V alloys

Microstructure, mechanical and tribological properties of multilayer TiAl/TiAlN coatings on Al alloys by FCVA technology

Impact tests of different frequencies can be applied to simulate the cyclic fatigue load of the tool under different working conditions as well as different impact frequencies. The main objective of the present article is to review different impact test methods for hard tool coatings. In this regard, impact tests are divided into three categories, including high-frequency, medium-frequency, and low-frequency tests. In terms of the impact scale, impact tests can be divided into micro-scale and nano-scale tests. The impact tests at micro-scales and nano-scales aim to characterize the coating substrate and the coating itself, respectively. It is found that the interface properties between the coating and the substrate have a remarkable impact on the fatigue resistance of the tool coating. Finally, the design and future development of the impact test are discussed.

Mechanical impact test methods for hard coatings of cutting tools: a review

Hard coatings play an important role in increasing the ability of deformation and wear resistance due to the superior mechanical and tribological properties. Nano-structured coating is now being used for cutting tool and exhibits extremely fascinating and useful properties. In milling process, a typical failure mechanism of coating is the cyclic mechanical impact between the workpiece and cutting tool. This could induce intensive fatigue failure of coated tools. In this work, a novel cyclic impact tester has been designed by using the piezoelectric ceramic actuator to study the fatigue resistance of bilayer micro-structured and multilayer nano-structured TiSiN/TiAlN coating. Besides, the mechanical, tribological and adhesion properties of coatings were evaluated. The multilayer nano-structured coating showed higher hardness yet toughness, better adhesion and tribological properties, as well as more superior properties of fatigue impact resistance. The influence of coatings on the wear behavior and cutting performance of cutting tools was investigated in milling Ti-6Al-4 V. The milling forces applied on the coated tools were measured and analyzed. It found that the friction force and normal force applied on the multilayer nano-structured coated tool were lower than that of bilayer micro-structured coated tool. The correlation between the mechanical properties in cyclic impact tests and cutting performance in milling experiments of coatings was studied. The multilayer nano-structured coated tool was much less susceptible to fatigue fracture and this could be attributed to the better fatigue resistance in the high frequency cyclic impact tests.

Investigation the fatigue impact behavior and wear mechanisms of bilayer micro-structured and multilayer nano-structured coatings on cemented carbide tools in milling titanium alloy

Introducing dynamic covalent bonding into thermoset polymers has received considerable attention because they can repair or recover when damaged, thereby minimizing waste and extending the service life of thermoset polymers. However, most of the yielded dynamic covalent bonds require an extra catalyst, high temperature and high-pressure conditions to trigger their self-healing properties. Herein, we report on a catalyst-free bis-dynamic covalent polymer network containing vinylogous urethane and disulfide bonds. It is revealed that the introduction of disulfide bonds significantly reduces the activation energy (reduced from 94 kJ/mol to 51 kJ/mol) of the polymer system for exchanging and promotes the self-healing efficiency (with a high efficiency of 86.92% after being heated at 100 °C for 20 h) of the material. More importantly, the mechanical properties of the healed materials are comparable to those of the initial ones due to the special bis-dynamic covalent polymer network. These results suggest that the bis-dynamic covalent polymer network made of disulfide and inter-vinyl ester bonds opens a new strategy for developing high-performance vitrimer polymers.

/pdf/self-healable-covalently-adaptable-networks-based-on-6dvj61ll.pdf

Self-Healable Covalently Adaptable Networks Based on Disulfide Exchange

Research on the Oxidation Resistance and Ultra-High Frequency Thermal Fatigue Shock Failure Mechanisms of the Bilayer and Multilayer Nano-Coatings on Cemented Carbide Tools

Covalent adaptable networks (CANs) have become sustainable alternatives to traditional thermosetting materials due to their powerful reprocessing and rearrangement capabilities. Therefore, developing and investigating reversible reactions that can be used in the construction of CANs is a popular research topic. Amino-yne click chemistry is known for its green characteristics—it is a catalyst-free and efficient reaction—and is widely applied in the synthesis of bio-organic molecules, but there have been few reports on CANs, especially multifunctional amine-based amino-yne click reactions. In this study, various CANs were synthesized via the amino-yne click reaction using multifunctional amines (diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA)), and they were compared with CANs that were prepared from a primary amine (tris(2-aminoethyl) amine (TREN) and a secondary amine (tris[2-(methylamino)ethyl]amine (TMEN)) under the same conditions. The results showed that H-DETA CANs exhibited the smallest glass transition temperature Tg (15 °C) and Young's modulus (105 MPa) because the crosslinker (DETA) contained a low content of primary amine and secondary amine, but its crosslinking density followed the trend of H-TMEN < H-DETA < H-TREN. In addition, the relaxation time, activation energy, and creep rate results for the CANs followed the same trend as the crosslinking density. With the increase in the secondary amine content of the multifunctional amines, the Tg of the CANs increased from 15 °C to 57 °C, the Young's modulus increased from 105 to 666 MPa, and the crosslinking density increased from 955 to 2690 mol/m3. Notably, the increase in the secondary amine content led to the weaker dynamics of the material, namely, prolonged relaxation time, increased activation energy, and decreased creep rate. This work also verified the dynamic exchange mechanism of the materials by the molecular model reaction and the amine solvent dissolution tests. Finally, hot-pressing experiments demonstrated the good plasticity and recovery ability of prepared CANs. This work provides an elegant path for preparing materials in energy and chemical fields such as coatings and rubber. 

Synthesis of dynamic polymers by amino-yne click reaction using multifunctional amine

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