Diamond is renowned for its high stability in extreme environments, such as high temperatures, high pressures, and strong corrosive conditions, which makes it demonstrate irreplaceable superior performance in quantum devices, high-power optical systems, and ultra-high-frequency electronic devices. Nevertheless, its intrinsic brittleness, difficulty in material removal, and vulnerability to damage caused by processing severely limit its practical application. The inherently rough surface of as-grown diamond necessitates precision polishing to obtain ultra-smooth, damage-free surface with nanometer-scale roughness, sub-micrometer form accuracy, and minimal subsurface damage. This paper provides a systematic review of state-of-the-art diamond polishing technologies, addressing the challenge of achieving sub-nanometer roughness and damage-free surface, with particular emphasis on the need for atomic-level surface integrity. The discussion covers laser polishing (LP), mechanical polishing (MP), ion beam polishing (IBP), gas cluster ion beam polishing (GCIBP), plasma polishing, dynamic friction polishing (DFP), chemical mechanical polishing (CMP), ultraviolet-assisted polishing (UVAP), plasma-assisted polishing (PAP), laser-assisted polishing (LAP), ultrasonic-assisted polishing (UAP), and other major techniques. By deconstructing these technological approaches, four fundamental material removal mechanisms, i.e., microfracture, graphitization, oxidation, physical sputtering and chemical etching, are identified. This highlights that hybrid, multi-physics polishing strategies can effectively balance the material removal rate (up to several μm·h⁻¹) and surface quality (down to sub-nanometer scale), outperforming conventional single-field techniques. Finally, the review outlines future directions, emphasizing innovations in multi-physics coupling mechanisms and intelligent control of atomic-scale manufacturing processes, thereby providing theoretical guidance and technical pathways to overcome the coupled challenges of atomic precision, efficiency, and extreme service conditions.

Material removal in the cutting process is regarded as a friction system with multiple input and output variables. The complexity of the cutting friction system is caused by the extreme conditions existing on the tool–chip and tool–workpiece interfaces. The critical issue is significant to use knowledge of cutting friction behaviors to guide researchers and industrial manufacturing engineers in designing rational cutting processes to reduce tool wear and improve surface quality. This review focuses on the state of the art of research on friction behaviors in cutting procedures as well as future perspectives. First, the cutting friction phenomena under extreme conditions, such as high temperature, large strain/strain rates, sticking–sliding contact states, and diverse cutting conditions are analyzed. Second, the theoretical models of cutting friction behaviors and the application of simulation technology are discussed. Third, the factors that affect friction behaviors are analyzed, including material matching, cutting parameters, lubrication/cooling conditions, micro/nano surface textures, and tool coatings. Then, the consequences of the cutting friction phenomena, including tool wear patterns, tool life, chip formation, and the machined surface are analyzed. Finally, the research limitations and future work for cutting friction behaviors are discussed. This review contributes to the understanding of cutting friction behaviors and the development of high-quality cutting technology.