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Ceramic composite cutter

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Update time : 2018-05-28 17:55:29

Demand for gas turbine engines with good fuel economy continues to increase, resulting in the replacement of traditional heat-resistant superalloy materials with new super tough high temperature and wear resistant alloys. The demand for new materials is booming and the demand for cutting tools for processing these materials increases simultaneously.
Manufacturers who need to cut these materials quickly realize that traditional processing guidelines alone cannot make them competitive. Tool makers are familiar with these machining challenges and have timely introduced cutting tools with high productivity and cost-effectiveness: ceramic composite tools.
Ceramic composites have excellent high temperature properties and high strength. This property makes ceramic composites a highly productive and stable tool material that can withstand the harsh cutting conditions of heat-resistant high-temperature superalloys and other difficult-to-machine materials.
Whisker reinforced ceramic tool
The most widely known ceramic composites for cutting heat-resistant superalloys are whisker-reinforced ceramics. Whisker-enhanced ceramic knives have emerged 30 years ago and have quickly captured the market with 10 times the productivity of carbide cutting tools. At the time, due to the lack of support for whisker reinforcement, ceramic cutters became incapable of cutting heat-resistant superalloys. Since then, with the application of whisker reinforcement technology, ceramic tools have demonstrated excellent performance in processing difficult-to-machine materials.
The coating whisker-reinforced ceramics that have emerged in the past decade have resulted in higher processing efficiency and lower production costs than non-coated whisker-reinforced ceramics. Like the coated carbide tool, the coated whisker reinforced ceramic insert enhances high temperature and wear resistance, further increasing productivity and extending tool life.
Upgrading non-coated whisker-enhanced ceramic tools to coated tools can increase cutting speeds by an average of 20% to 40%. According to the different materials of the coated tool, the feed speed can be increased by 20%, and the tool life can be extended by 50% to 100%. In many applications, coated tools have a smoother surface finish and a longer cutting length than uncoated tools.
Using a ceramic composite tool is not as simple as attaching the insert to the knife pocket and starting the machine run button. The user must master the basics of the performance improvement, precision measurement and tool wear adjustment of these tools.
ceramic cutting tool
Correct use
Whisker-reinforced ceramic inserts are made of fine-grained alumina and silicon carbide crystals called whiskers. Al2O3 is a high-temperature, wear-resistant material, but lacks sufficient strength and therefore its cutting performance is not stable. Just like adding reinforcing steel to cement and adding fiber to glass steel, Al2O3's strength can be improved and its performance can be improved by adding silicon carbide whiskers. Whisker-reinforced ceramic tools can cut at higher speeds than conventional carbide tools.
High cutting speeds are crucial for the plasticization or softening of heat-resistant superalloys. The plasticized material can be efficiently removed layer by layer. However, the plasticization process generates a lot of heat in the cutting area. Cutting heat needs to be effectively eliminated, so that the microstructure of the base metal is not affected. Therefore, it is necessary to properly balance the cutting speed and feed rate and maintain the correct average chip thickness (ACT) so that a large amount of cutting heat can be taken away by the chip.
The feed rate is described by ACT instead of feed per revolution or feed per tooth because the chip thickness changes due to changes in the feed rate and many other factors. For example, the ACT of a circular insert is related to the depth of cut, because a change in depth of cut causes the effective leading angle of the tool to change, making the chips thicker or thinner.
When using a straight-edged blade, the ACT is related to the direction of the tool relative to the part, which is related to the primary declination angle. The use of a tool with a leading angle has a number of advantages, such as preventing the ceramic tool from being chipped, but it is important at this point to adjust the programmed feed rate to avoid chip thickening and to ensure predictable tool wear.
The empirical value of the whisker reinforced ceramic insert ACT is 0.002" to 0.004" (0.05 mm to 0.10 mm). This value ensures that the chip maintains the proper cross-sectional dimensions to remove the large amounts of heat generated by the high cutting speeds between the tool and workpiece interface.
Too thin chips will not carry enough heat. As a result, heat will be transferred to the parent material. In addition, excessively thin chips will cause the tool and the workpiece to rub instead of the tool cutting the workpiece, and accelerate the flank wear to make the tool premature failure. The opposite effect of excessive chip thickness will lead to increased pressure on the blade and chipping or breaking of the blade.
According to the composition of the material to be cut, the cutting speed and feed speed must be properly adjusted. In addition, it is particularly noteworthy that the hardness of the material to be cut, the hardness of the material needs to use a lower cutting speed to plasticize the parent material to a certain extent before they can be effectively removed.