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Difficult-to-machine materials (DMMs) are extensively applied in critical fields such as aviation, semiconductor, biomedicine, and other key fields due to their excellent material properties. However, traditional machining technologies often struggle to achieve ultra-precision with DMMs resulting from poor surface quality and low processing efficiency. In recent years, field-assisted machining (FAM) technology has emerged as a new generation of machining technology based on innovative principles such as laser heating, tool vibration, magnetic magnetization, and plasma modification, providing a new solution for improving the machinability of DMMs. This technology not only addresses these limitations of traditional machining methods, but also has become a hot topic of research in the domain of ultra-precision machining of DMMs. Many new methods and principles have been introduced and investigated one after another, yet few studies have presented a comprehensive analysis and summarization. To fill this gap and understand the development trend of FAM, this study provides an important overview of FAM, covering different assisted machining methods, application effects, mechanism analysis, and equipment design. The current deficiencies and future challenges of FAM are summarized to lay the foundation for the further development of multi-field hybrid assisted and intelligent FAM technologies. The recent advancements of the field-assisted machining techniques are reviewed. Basic principles, equipment design, and typical applications of different field-assisted machining methods are summarized. The rational selection and effectiveness of energy field in field-assisted machining are presented. Challenges and prospects of field-assisted machining are orchestrated.

The substitution of biolubricant for mineral cutting fluids in aerospace material grinding is an inevitable development direction, under the requirements of the worldwide carbon emission strategy. However, serious tool wear and workpiece damage in difficult-to-machine material grinding challenges the availability of using biolubricants via minimum quantity lubrication. The primary cause for this condition is the unknown and complex influencing mechanisms of the biolubricant physicochemical properties on grindability. In this review, a comparative assessment of grindability is performed using titanium alloy, nickel-based alloy, and high-strength steel. Firstly, this work considers the physicochemical properties as the main factors, and the antifriction and heat dissipation behaviours of biolubricant in a high temperature and pressure interface are comprehensively analysed. Secondly, the comparative assessment of force, temperature, wheel wear and workpiece surface for titanium alloy, nickel-based alloy, and high-strength steel confirms that biolubricant is a potential replacement of traditional cutting fluids because of its improved lubrication and cooling performance. High-viscosity biolubricant and nano-enhancers with high thermal conductivity are recommended for titanium alloy to solve the burn puzzle of the workpiece. Biolubricant with high viscosity and high fatty acid saturation characteristics should be used to overcome the bottleneck of wheel wear and nickel-based alloy surface burn. The nano-enhancers with high hardness and spherical characteristics are better choices. Furthermore, a different option is available for high-strength steel grinding, which needs low-viscosity biolubricant to address the debris breaking difficulty and wheel clogging. Finally, the current challenges and potential methods are proposed to promote the application of biolubricant.

Difficult-to-machine materials are characterized by high hardness, strength, and anisotropy. During machining, tools can suffer from adhesion, abrasion, material detachment, and high cutting temperatures. These factors result in severe adhesive wear, abrasive wear, oxidative wear, and diffusion wear. Intense tool wear leads to more burrs, delamination, chipping, and dimensional errors in the parts. It significantly increases production costs and reduces machining efficiency. Therefore, further research into tool wear is of great importance. This paper reviews the characterization and monitoring of tool wear, the morphology and mechanism of wear, and measures for improving wear, with a focus on tool wear in the machining of difficult-to-machine materials. Through a comprehensive review of existing research findings, this work offers a perspective on the investigation of tool wear, providing an effective guide for future research. And it is of great significance to improve tool life and cutting quality.

With the rapid development of aerospace and defense industries, the shape of products is becoming more and more complex, and the requirements for product processing accuracy and surface quality as well as tool life are getting higher and higher. Ultrasonic elliptical vibration cutting (UEVC) can overcome the limitations of traditional cutting methods in difficult-to-machine materials, high surface integrity and high performance and have been widely used, especially in the processing quality and performance assurance of hard and brittle materials such as ceramics, glass, composite materials and cemented carbide. At the same time, in the expansion from the field of manufacturing and processing to the fields of biomedicine and micro–nano-manufacturing, the requirements for precision are almost strict, which poses higher challenges to UEVC technology and its devices. With this trend, many new UEVC devices and applications have been put forward, however, few people have studied them from a comprehensive perspective. In order to fill this gap in literature and understand the development trend of UEVC, this study gives an important overview of UEVC, including its cutting characteristics, device development and application in difficult-to-machine materials. Firstly, the advantages brought by the cutting characteristics of UEVC are analyzed. Next, the development status and shortcomings of UEVC devices with different excitation modes in structural design and optimization are discussed, and their advantages and disadvantages are compared and analyzed. Then, the application of UEVC in difficult-to-machine materials in recent years is expounded, and the influence of various cutting parameters on tool wear and surface quality is analyzed. Finally, a summary of the full text is made, and several prospects for the future development of UEVC are proposed, which points out the direction for future research.

The properties of the Inconel 718 superalloy are used in the manufacturing of aircraft components; its properties, including high hardness and toughness, cause machining difficulties when using the conventional method. To circumvent this, non-conventional techniques are used, among which electrical discharge machining (EDM) is a good alternative. However, the nature of removing material using the EDM process causes the thermophysical properties of Inconel 718 to hinder its machinability; thus, a more extensive analysis of the influence of these properties on the EDM process, and a machinability analysis of this material in a wider range, using more process parameters, are required. In this study, we investigated the drilling of micro-holes into the Inconel 718 superalloy using the EDM process. An experiment was conducted to evaluate the impact of five process parameters with a wide range of values (open voltage, time of the impulse, current amplitude, the inlet dielectric fluid pressure, and tube electrode rotation) on the process’s performance (drilling speed, linear tool wear, the side gap thickness, and the aspect ratio of holes). The analysis shows that the thermal conductivity of this superalloy significantly influences the effective drilling of holes. The combination of a higher current amplitude (I ≥ 3.99 A) with an extended pulse time (ton ≥ 550 µs) can provide a satisfactory hole accuracy (side gap thickness ≤ 100 µm), homogeneity of the hole entrance edge without re-solidified material, and a depth-to-diameter ratio of about 19. Obtaining a high dimensional shape accuracy of holes has an enormous effect on their usability in the structure of the components in the aviation industry.

In micromachining, the quasi-intermittent vibration—assisted swing cutting technology alleviates the residual height problem of elliptical vibration–assisted cutting (EVC) and inherits its intermittent machining characteristics. The minimum chip thickness has a significant impact on cutting forces, tool wear, and process stability when working with difficult-to-machine materials. This study thoroughly examines the impact of cutting parameters and tool parameters on the quality of the workpiece during machining in order to better understand the time-varying characteristics of the quasi-intermittent vibration–assisted swing cutting (QVASC) machining process and the size effect on micro-cutting of silicon carbide crystal. This paper created the minimum chip thickness prediction model suited to QVASC machining process. The effects of variables such as cutting velocity and tool inclination on the minimum chip thickness were discussed as well as the scribing tests that were conducted on such challenging materials as silicon carbide. The research findings shown that during the machining process, the critical undeformed chip thickness of silicon carbide decreased continuously as the cutting velocity sequentially increased (1.51 mm/min, 1.88 mm/min, 2.26 mm/min); under the down inclination angle (0–10°), the critical undeformed chip thickness also continuously decreased. These results confirm that cutting too fast reduces the instantaneous undeformed chip thickness, which is not conducive to ductile removal.

Difficult-to-machine material thin-walled parts with curved surface are widely used in industrial applications, and the shape accuracy is a basic requirement for ensuring the usability. Due to the low rigidity of the thin-walled curved surface parts, the cutting force becomes a sensitive factor for the machining deformation. In addition, high speed milling, that has an obvious attribute of small cutting force comparing with the traditional one, provides an effective way to process the thin-walled curved surface parts made by difficult-to-machine materials like titanium alloy. Moreover, the rigidity of the thin-walled curved surface parts is constantly changing along with the machining process, which leads to a more complex machining deformation when choosing different tool paths and affects the machining quality. To reduce the machining deformation, a proper cutting parameters combination which influences the machining deformation directly is obtained based on the established cutting force model, and then a deformation control strategy by planning tool path is put forward. At the same time, an efficient compensation method based on modifying cutter location point is proposed. Taking TC4 thin-walled arc-shaped parts as an example, experimental studies indicate that the largest deformation values reduce to 49 μm after compensation. Compared with the former 104 μm, the deformation degree decreases by 52.88 % when the thickness of the thin wall is 200 μm. The research provides an effective approach to reduce the machining deformation induced error for difficult-to-machine material thin-walled parts with curved surface.

The fabrication of miniature structures on components with high-integrity surface quality represents one of the cutting edge technologies in the 21st century. The materials used to construct such small structures are often difficult-to-machine. Many other readily available technologies either cannot realise necessary precision or are costly. Abrasive waterjet (AWJ) is a favourable technology for the machining of difficult-to-machine materials. However, this technology is generally aimed at large stock removal. A reduction in the scale of this technology is an attractive avenue for meeting the pressing need of industry in the production of damage-free micro features. This paper reviews some of the work that has been undertaken at UNSW Sydney about the development of such an AWJ technology, focusing on the system design currently employed to generate a micro abrasive jet, the erosion mechanisms associated with processing some typical brittle materials of both single- and two-phased. Processing models based on the findings are also presented. The review concludes on the viability of the technology and the prevailing trend in its development.

Traditional mechanical processing techniques are confronted with significant challenges when machining advanced materials possessing excellent mechanical properties. Electrochemical machining (ECM), as a material removal technology based on the principle of anodic dissolution, demonstrates distinctive advantages including the absence of contact stress, independence from material hardness, and elimination of mechanical residual stress and recast layers. These characteristics render ECM particularly suitable for high-precision applications requiring superior surface quality. This review systematically summarizes the applications, recent progress, and current challenges of ECM in surface processing. According to diverse surface requirements, ECM technology is classified into two core directions based on primary objectives. The first direction focuses on surface quality enhancement, where nanoscale planarization, residual stress reduction, and uniform surface performance are achieved through precise regulation of anodic dissolution. The second direction concerns material shaping, which is subdivided into macro-scale and micro-scale processing. Macro-scale forming combines electrochemical dissolution with mechanical action to maintain high material removal rate (MRR) while achieving micron-level precision. Micro-scale forming employs nanosecond pulse power supplies and precision electrode/mask designs to overcome manufacturing limitations of micro-nano features on hard-brittle materials. Despite progress achieved, key technical bottlenecks persist, including unstable dynamic control of the inter-electrode gap, environmental concerns regarding electrolytes, and tooling degradation. Future research should prioritize the development of green processing technologies, intelligent control systems, multi-scale manufacturing strategies, and multi-energy field hybrid technologies to enhance the capability of ECM in meeting increasingly stringent surface requirements for advanced materials.

Ultrasonic vibration-assisted cutting (UVAC) has been regarded as a promising technology to machine difficult-to-machine materials. It allows for a sub-micrometer form accuracy and surface roughness in the nanometer range. In this paper, high-frequency vibration-assisted sculpturing is used to efficiently fabricate quadrilateral microlens array with sharp edges, instead of using slow-slide-servo diamond turning with vibration. The machining principle of diamond sculpturing, the cutting dynamics of ultrasonic vibration, and the tool edge on the theoretical form error between the designed structure and the machined structure were investigated for this technique. Then, the quadrilateral microlens array was machined by means of conventional sculpturing (CS) and high-frequency ultrasonic vibration-assisted sculpturing (HFUVAS), respectively, followed by a study of the cutting performances including form accuracy, the surface morphology of the machined structure, and the tool wear. Results showed that conventional sculpturing fabricated microlens array with poor form accuracy and surface finish due to couple effect of material adhesion and tool wear, while the high-frequency ultrasonic vibration-assisted sculpturing achieved optical application level with sub-micrometer form accuracy and surface roughness of nanometer due to reduction of material adhesion and tool wear resulted from high-frequency intermittent cutting.