The hottest stress relief optimizes the well-desig

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Stress relief: optimize the well-designed coating function

Sandvik croman has been exploring how to produce a low stress coating that can utilize any residual stress for the benefit of all amputees, thereby benefiting the overall blade performance. The result of this study is that several new blade brands have been introduced. Here we mainly look at stress and its role in blade performance

the main function of tool coating is to improve the production efficiency by increasing the cutting speed or the competition rate after several hours of feeding. The driving factor of the introduction of any new blade coating is to determine the possible causes of blade failure and develop coating properties that can clearly deal with these problems. A well-designed coating, each aspect has different functions; It is a combination of coating process and coating materials to prevent blade failure and promote blade to play a better performance

coating has become an integral part of modern cutting tool materials, and the vast majority of blades sold today adopt various coating technologies. The multi-layer coating is formed by stacking several thin layers, and each layer is separated by an intermediate layer. Using multi-layer coating, people can change the characteristics of each coating according to specific processing operations, and ensure that the coating and tool substrate work harmoniously, so it is increasingly popular

gc4225 visible low stress

with multi-layer coating, the blade can benefit from the combination of the properties of each layer, so as to optimize the metal removal accuracy and 7-bit removal rate. By adding several layers of coating, tool makers can produce blades with specific performance according to specific materials or applications, and can also produce blades with wide performance, which can be used to deal with various materials or applications

now, people use Sandvik's multi-layer coating on gc4225 for turning and gc4240 for grinding. It is also used on gc3205, gc3210, gc3215 and gc3220 for turning. They use titanium nitride carbide (TiCN), aluminum oxide (Al2O3) and titanium nitride (TIN), plus a variety of intermediate thin coatings

generally speaking, the materials used in various tool applications should bear both internal and external stresses. As far as the blade is concerned, the external stress is the stress borne as part of the cutting tool in the operation. The manufacturing process of the blade will also introduce internal stress, mainly tensile stress and compressive stress. At the coating temperature, the coating and substrate are free from stress. The expansion coefficient of the coating is large, so the shrinkage of the coating will be greater than that of the substrate when cooling. This will cause tensile stress on the surface and compressive stress on the substrate. These surface stresses will form surface cracks and further spread downward. By reducing the tensile stress, this cracking "tendency" will be greatly reduced, and the blade can also withstand more improper use

therefore, from a functional point of view, it is very important to eliminate the tensile stress as much as possible, because the tensile stress is the main factor causing crack propagation. Researchers have carefully designed the molecular structure of hydrophilic polyurethane resin. Compressive stress is often advantageous and can help to suppress crack propagation

common properties

inevitably, tool substrates and coatings have similar properties. Both require high hardness, fracture toughness and wear resistance

multilayer coating also helps to include other parameters that cause mismatch between coating and substrate and cause stress. For example, the coefficient of thermal expansion determines the interfacial thermal mismatch stress between the coating and the substrate

the combination of wear-resistant coating and tool surface is a key requirement, because unless the coating is well combined with the tool, the coating cannot play a role. In the coating process of chemical coating, it is relatively easy to achieve good bonding by forming a diffusion inducing interface between the coating and the substrate

the medium temperature chemical vapor deposition (mt-cvd) process and the new post-treatment process of stress reduction account for a large part of the achievements made by Sandvik croman. Mt-cvd process is used for titanium nitride carbide or titanium oxide coating. Its tensile stress value is often low, which is more suitable for the combination of fracture toughness, wear resistance, chemical wear resistance and heat cracking resistance. This can improve the performance of the blade

process considerations

process determines the structure of the blade, and the blade structure determines the properties of the blade. Thus, the columnar direction and ideal particle size of the coating crystal are formed. The crystal is in the longitudinal direction, and the surface is harder, which is the place where the wear occurs. In addition, the decreasing stress lines between the crystals dissipate the mechanical stress into the base material. The bond length between the atoms of the material is shortened, which also helps to eliminate tensile stress. If micro cracks are caused by high temperature and mechanical impact and penetrate the surface coating, these micro cracks will dissipate downward along the stress line between crystals. When the residual stress reaches the base, it will be absorbed instead of spreading into larger cracks. In this way, the blade has toughness and strength

mt CVD titanium nitride carbide is used in combination with oxide coatings such as aluminum oxide (Al2O3). The coating is a fine-grained, columnar α Phase alumina coating. This is a very hard material, which provides a temperature barrier to protect the inner body of the tool from additional high temperature

the post-treatment process developed by Sandvik clement is the final stage of blade production process. It forms a low stress blade coating and a smooth coating surface. It also tries to close the cooling cracks by bridging the cooling cracks near the coating surface

mt CVD titanium nitride carbide is used in combination with oxide coatings such as aluminum oxide (aluminum oxide)

the coating is a fine-grained, columnar α Phase alumina coating protects the inside of the tool from additional high temperature


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