News Center

Machining places stringent demands on cutting tools while also seeking to minimize environmental pollution.

　　Approximately 70% of premature failures in various electromechanical products are attributable to wear and corrosion, both of which are closely linked to the material’s surface condition—encompassing its physical, chemical, and stress states. Consequently, enhancing the service performance of such materials hinges on improving their surface properties.

　　With the advancement of science and technology, the demands on material surface properties have grown ever higher. Over the past few decades, the emergence of various vapor-phase deposition techniques has propelled both the research and practical applications of surface engineering to unprecedented levels. These technologies not only meet mechanical performance requirements—such as wear resistance, friction reduction, and corrosion protection—but also excel in functional materials fields related to surface layers, including electromagnetics, optics, optoelectronics, thermodynamics, superconductivity, and biology. Surface engineering not only enhances the performance‑to‑cost ratio of inexpensive metallic materials but has also become a crucial approach for developing novel coatings and thin‑film materials, holding immense potential for a wide range of applications.

　　As the level of mechanical machining continues to advance, new demands are being placed on cutting tools. In addition to extending tool life, there is a growing need to minimize contamination during machining and to favor dry cutting whenever possible. When it is not feasible to eliminate cutting fluids entirely, efforts should be made to formulate them with only rust inhibitors and no organic compounds, thereby significantly reducing the costs associated with recycling and reuse.

　　The diversity of cutting tools and the specific operating conditions under which they are used dictate the selection of appropriate tool coatings. Turning differs from drilling, and milling cutters must also account for their intermittent impact characteristics. Early coating technologies prioritized wear resistance, with hardness as the primary performance metric. Coatings such as titanium nitride exhibit relatively high coefficients of friction (0.4–0.6); during machining, the continuous friction between the coating and the workpiece generates substantial heat. To prevent excessive tool heating, deformation, and consequent loss of machining accuracy, as well as to extend tool life, cutting fluids are typically employed.

　　To address the issues associated with cutting fluids—whether through reduction or elimination—tool coatings must not only ensure long tool life but also provide self‑lubricating properties. Diamond‑like carbon (DLC) coatings have demonstrated advantages in machining certain materials, such as aluminum, titanium, and their composites. However, years of research have revealed three major drawbacks: high internal stresses, poor thermal stability, and a catalytic effect with ferrous metals that induces a structural transition from sp³ to sp². These limitations currently restrict DLC coatings to non‑ferrous metal machining, thereby limiting their broader application in metalworking. Recent studies, though, indicate that DLC coatings dominated by an sp² structure—also referred to as graphite‑like coatings—can achieve hardness levels of 20–40 GPa while avoiding the catalytic interaction with ferrous metals. They exhibit low friction coefficients and excellent resistance to moisture, allowing for use with coolants or even dry machining. Moreover, their service life is several times longer than that of uncoated tools, and they pose no problems when machining steel and other ferrous materials. As a result, these coatings have attracted significant interest from coating manufacturers and tool producers. Given sufficient time, this new class of diamond‑like carbon coatings is poised to find widespread adoption in the cutting‑tool industry.