The choice of diamond coating thickness is not "the thicker the better", the improvement of wear resistance, the quality of the diamond coating is more important than the thickness. With the full-scale explosion of the 3D glass market, the excellent performance of graphite materials in the application of 3D glass hot bending molds has been unanimously recognized by the industry. Due to the high abrasiveness and toughness of graphite materials, the processing environment requirements for graphite molds are very strict. In order to ensure that the graphite mold has good precision, smoothness, and stability, in addition to the need for quietness and the dust-absorbing ability of the fuselage itself, graphite processing tools have also become the top priority in the processing process. Selecting tools suitable for high-speed processing requires from From the perspective of improving durability, reliability and safety, comprehensive consideration should be given to the matching of tool substrate and coating material and tool and workpiece material.
After continuous experiments and verification of various tool materials, the service life of CVD diamond-coated tools is 8-10 times that of cemented carbide tools, and the allowable cutting speed of CVD diamond-coated tools is 2-3 times higher than that of cemented carbide tools. The blade is sharp and consistent, and the friction coefficient is low. It can realize high-speed and high-precision machining of thin-walled graphite molds at high speed and low feed rate. At the same time, the service life of CVD diamond-coated tools is limited by various graphite processing manufacturers among many tool materials. of all ages!
Chemical vapor deposition (Chemical Vapor Deposition, referred to as CVD) diamond coating has many excellent properties such as high hardness, high thermal conductivity, low friction and low expansion coefficient close to natural diamond. When processing brittle materials such as graphite and carbon fiber composite materials, It has become the surface coating of cutting tools, showing excellent performance in improving tool life and machining quality.
According to the grain size, CVD diamond coating can be divided into micro-diamond coating and nano-diamond coating. The grain size of the micron diamond coating is usually between 500 nm and several microns. It is formed by the competitive growth of columnar diamond grains. It has excellent characteristics such as high hardness and good surface wear resistance, which can significantly reduce the tool wear rate. Improve tool life. However, the surface of the micron diamond coating is relatively rough (the Ra value is usually a few hundred nanometers), and the coating toughness and crack resistance are poor. Before blunting the standard, the coating has peeled off. The nano-diamond coating is composed of nano-scale diamond grains distributed in clusters, the grain size is usually below 100 nm, the surface smoothness is good (Ra value is less than 100 nm), and the friction can be significantly reduced during the cutting process, thereby Reduce cutting force and cutting heat, improve tool life. Nano-diamond coating has a good ability to resist crack propagation. However, compared with micro-diamond, its bonding strength with the substrate is relatively low, and it is prone to abnormal failures such as coating peeling off during processing.
The main basis for the selection and application of diamond-coated tools is the properties of the workpiece material and the processing quality requirements. For EDM graphite mold processing, the essence of the milling process is similar to the "grinding" process. At this time, the number of "micro-cutting edges" on the tool surface is large and wear-resistant, and a micron diamond coating with a larger grain size should be selected. For molds used in ceramic processing, high surface finish is required, and nano-diamond coating should be used in the finishing stage. In the processing of aluminum alloys, the severity of the "sticking tool" phenomenon is higher than that of tool wear. At this time, the requirements for tool wear resistance are relatively low, and nano-diamond coatings with low friction coefficients should be selected. For carbon fiber composite materials, due to the strong abrasiveness of the fiber material itself, it is required that the tool has good wear resistance and reduce the cutting force and cutting heat during processing. Micro/nano composite diamond coating should be used. In particular, the choice of the thickness of the diamond coating is not "the thicker the better", the improvement of wear resistance, the effect of the quality of the diamond coating is greater than the effect of the thickness.