The blade is a typical free-form surface part. When processing this kind of parts, there is a characteristic: thin, easy to deform during processing, and the material is usually stainless steel, Monel alloy, INCONEL, titanium and nickel-based difficult-to-machine alloy materials. It increases the difficulty of processing, and puts forward higher requirements on processing technology and processing tools.
In the processing of blades, there are three difficulties in blade processing: milling process surrounding area, blade root processing, and milling of rib holes.
For aircraft, the normal operation of the engine is the most important one. To ensure the safe operation of the engine, the quality of the blades must pass strict inspections! Blade inspection is mainly size and shape inspection, as well as crack inspection.
1) Size and shape detection
There are many blades on an engine, and there are about 30 blades on each disk. If the shape and size of the blades cannot be guaranteed, it is very dangerous when the engine is running at high speed. Therefore, it is also very important to detect the shape and geometric size of the blade, but the conventional measurement method is difficult to measure the shape of the blade. Therefore, scientists have developed a three-coordinate measurement system to establish a model by establishing measurement data. Determine the difference in the shape and size of the blade.
2) Crack detection
Cracks are the most fatal defect of engine blades. The working conditions of aero-engine blades are very bad, causing the blades to be often subjected to impacts and frictions. At the same time, they also endure high-temperature burning and thermal fatigue. The blades are prone to various cracks. If they cannot be found and dealt with in time, they will be affected. The flight safety of aircraft poses a great threat, so it is always the pursuit of scientists to adopt effective methods to find cracks in the blades.
At present, common detection methods include CTI technology, TOFD technology, infrared technology, UT technology, etc.
Below we briefly describe how to manufacture turbine blades for aero-engines:
Process porcelain clay, break the porcelain clay to make the inner core of the turbine blade.
Workers check and modify the shaped porcelain clay models one by one, and the finished porcelain clay models will first be sintered into a fused silica ceramic core.
Turbojet engines require hollow turbine blades. Only a high-quality ceramic core is the best core material for lost wax casting. It can remain stable when casting metal, and can be easily dissolved by chemical processes after the casting is cooled. Leave the required air channels in the blades.
The porcelain clay model waiting to be processed is wrapped with beeswax on the outside for lost-wax casting to obtain turbine blades. The porcelain clay model is actually the air passage in the blade. When the engine is running, air passes through it, so as to cool the turbine blade and keep it stable.
Prepare the casting interface, these interfaces will be equipped with two to four blades, so that the efficiency of casting molten metal can be improved. Wrap the ceramic core with beeswax to form a cavity in the casting mold.
After installing the beeswax blades on the casting interface, you can see that the beeswax blades that have been wrapped with the ceramic core look strong in structure, but they are all metal runners during casting, and the blades are actually very small. Final processing of the blades so that the molten metal can fill the cavity without causing casting blisters. At this point, the casting model was finally processed.
The next step is to wrap these cast models with porcelain clay to make pottery models. Workers install the casting model on a rotating machine. Use the manipulator to rotate in the clay liquid to make it evenly wrap any part of the model. Only in this way can it be considered qualified. After adding it into a special wind box, spray porcelain clay on the surface to form a thick shell. Let it air dry.
After that, the casting model is cast in the precision casting workshop. The first step is to heat up and burn the porcelain clay wrapped around the cast model into a ceramic model. At the same time, the beeswax inside is discharged to form a casting cavity. The worker took out the casting model. These models will then cast special alloy solutions. Each model requires a special furnace for processing. The model production temperature of large parts is very high.
Finally, the blades produced need to be X-ray inspected. Each blade must be inspected from multiple angles to prevent any defects. X-ray photos, you can see the cavity inside the blade.
The entire turbine blade production process is very complicated, completely surpassing the jewelry manufacturing industry, and this is only a small part of aero engine manufacturing. The complete blade design and manufacturing include: blade structure design, blade strength design, blade material design, and blade manufacturing process design. Failure mode analysis during blade use, etc.
Post time: Jun-18-2021