With the continuous development of machining industry, people put forward many new requirements for the cutting tools used. These requirements are not only limited to the size, shape and material of the tool, but also in other aspects, such as the coating and dry cutting performance of the tool, which are increasingly becoming important indicators to measure the performance of the tool.
Tool coating and surface engineering.
The main goal of early coating is to improve the hardness and wear resistance of tools. At that time, the coating material was represented by titanium nitride, which had a large friction coefficient and would produce a lot of friction heat when cutting the workpiece, which was not conducive to the processing.
Now, the diversity of cutting tools and their different working conditions determine that the coatings used are very different. For example, the coating used by turning tools and drilling tools is quite different, and the intermittent impact characteristics of milling tools should be considered when selecting the coating. The rapid development of surface engineering technology is inseparable from the rise and maturity of various vapor deposition technologies in recent decades.
Vapor deposition technology is a technology that uses the physical and chemical effects in the gas phase to form metal, non-metal or compound coatings with certain functions or as decorations on the surface of workpieces. According to the coating mechanism, this technology can be divided into three types: chemical vapor deposition, physical vapor deposition and plasma vapor deposition. Vapor deposition technology not only realizes the mechanical properties of cutting tools, such as wear resistance, friction reduction and corrosion resistance, but also has the opportunity to show its talents in the fields of electromagnetic, optical, optoelectronic, thermal, superconducting and biological functional materials related to the surface layer.
Surface engineering not only enables low-cost ordinary metal materials to show the ability of high-quality metal materials in cutting performance, but also has become an important means to develop various new coatings and film materials, which has great application potential.
Clean and environmentally friendly cutting method
In addition to cutting performance and service life, people's requirements for cutting tools also include that the machining process should be as clean and environmentally friendly as possible to reduce the pollution caused in the cutting process. As cutting fluid is one of the main pollution sources of machining, it is in line with the purpose of clean and environmental protection that dry cutting gradually replaces the original traditional cutting methods.
Dry cutting is a technology of cutting without using cutting fluid and without cold liquid. To adopt dry cutting, we must ensure that we can still complete the processing task with high quality and high quality without using cutting fluid, and do not damage the service life of the tool. To achieve this, it depends on high-quality tool coating.
According to the research results of experts, to solve the problem of reducing or eliminating cutting fluid, the tool coating should not only make the tool have a long life, but also have the function of self-lubricating. Previously, diamond coating was used to achieve this purpose. However, diamond coating has three irreparable disadvantages: first, high internal stress, second, poor thermal stability, and third, it is easy to have catalytic effect with ferrous metals, so it can only be used to process non-ferrous metals, and is not an ideal coating material.
The appearance of DLC coating solves this problem perfectly. Many research results in recent years have shown that the diamond-like coating with SP2 structure, also known as graphite like coating, has a high hardness, which can reach 20 to 40gpa, without catalytic effect with ferrous metals; Its friction coefficient is very low, and it has good moisture resistance, which can effectively improve the service life of tools, and has been widely used in the field of machining.
In most cases at this stage, the use of cutting fluid can not be completely banned. At this time, we should try to make it contain only antirust agents and no organic substances. This can not only reduce environmental pollution, but also greatly reduce the cost of recycling.