Carbon fiber reinforced composite materials have the advantages of light weight, high strength, etc., and have been widely used in the aerospace field in recent years. Titanium alloy has excellent properties such as high strength, low density and good heat resistance. In the field of aerospace manufacturing, CFRP and Ti-6V-4V alloys are often used together, and the two need to be connected by bolts, so drilling is required, and there are few research reports on the drilling of this material. For this reason, super-hard drill bits were used to drill the laminated materials of CFRP and Ti-6V-4V alloy, the relationship between cutting conditions, tool coating types and tool wear was studied, and the optimal cutting conditions were discussed.
The experiment uses 4 kinds of coating hard drills (Φ6 mm), which are TiAlN coating hard drill, TiAlCr/TiSi coating hard drill, TiSiN coating hard drill and AlCrSiN coating hard drill. The processed material is a laminated material of CFRP (thickness 3 mm) and Ti-6V-4V alloy (thickness 9.5 mm). The cutting speed was 18.8 m/min and the feed rate was 0.2 mm/r. The experiment was conducted under two conditions, dry and wet. The flow rate of water mist during wet cutting was 100 mL/h. The pressure applied from inside the bit is 0.35 MPa. Measure the thrust, torque and wear of the cutting surface of the drilled material during drilling, and observe the surface condition of the processed hole. When the cutting surface of the drill bit wears up to 0.2 mm, it is defined as the end of tool life, and the experiment is terminated.
Experiment shows that when drilling CFRP, its thrust and torque change little with the cutting conditions; when drilling titanium alloy, its thrust is smaller than that of dry cutting under wet conditions. The torque when drilling titanium alloy does not change much when the cutting distance is less than 375 mm (N=30, N is the number of holes), and when the cutting distance is more than 1 125 mm (N=90), the torque under wet conditions increases sharply Big. Observation of the tool wear shows that the TiAlCr/TiSi coated hard drill has the least wear, followed by AlCrSiN coated drill. Compared with the dry and wet conditions, it can be seen that the tool life is longer when wet drilling is used. This is because the use of water mist reduces the cutting temperature, thereby reducing the wear of the tool. Observation of the surface of the drilled hole and the inner wall of the hole shows that the dry layer drilling has a delamination phenomenon on the inner wall of the CFRP. During wet drilling, the connection side of the CFRP and the titanium alloy shows burns, which is caused by the increase in the cutting temperature of the titanium alloy. of. In addition, in the wet drilling, the inner wall of the titanium alloy hole is damaged. This is because the double-edged drill used with the tool wear increases, the cutting resistance balance of the two blades is destroyed, causing the second blade to jump on the machining inner wall. There is titanium adhesion on the second cutting surface, which is the phenomenon of double-edged drills. However, when using single-edge drill dry cutting, there is no such phenomenon of adhesion of titanium alloy.