High-temperature alloys (also known as heat-resistant superalloys) are a type of metal material that can work for a long time at high temperatures of 600℃-1000℃ and under certain stress. They are made of iron, cobalt, and nickel as matrix elements, fused with other metals or non-metallic elements. Compared with ordinary metals, high-temperature alloys have excellent oxidation resistance and corrosion resistance, fatigue resistance and fracture toughness.
Classification and application of high-temperature alloys
High-temperature alloys can be further subdivided into iron-based alloys, cobalt-based alloys, and nickel-based alloys.
1. Iron-based alloys: low-cost, mainly used for low-temperature aerospace engines and industrial gas turbine discs, casings, shafts and other parts, as well as some load-bearing parts and fasteners.
2. Cobalt-based alloys: mainly used for guide blade materials. Due to the scarcity of cobalt resources, the price of this type of alloy is relatively high.
3. Nickel-based alloys: widely used in the manufacture of high-temperature components of turbojet aircraft engines and industrial gas turbines, such as turbine part working blades, guide blades, etc. Nickel-based high-temperature alloys account for more than half of the high-temperature alloy market, and representative alloys include Inconel 718, Waspaloy, and Udimet 720.
Difficulties in processing high-temperature alloys
Poor thermal conductivity
The thermal conductivity of high-temperature alloys is only 1/5 to 1/2 of that of 45 steel, resulting in high cutting temperatures and extremely high requirements for the high-temperature resistance of the tool.
Complex processes
The processing of high-temperature alloys involves multiple heat treatments, forging, casting, and other process steps, which are complex and extend the processing cycle.
High cost
Due to the high hardness and high-temperature resistance of high-temperature alloys, high-hardness cutting tools and special tools are required for processing, which increases the wear and replacement costs of cutting tools and increases the overall processing cost.
Material loss
Traditional processing methods will generate a large amount of cutting waste and chips, and the tool is prone to the built-up edge, which affects the quality of the processing surface, increases the loss of raw materials, and brings environmental problems.
Difficult processing
The hardness and brittleness of high-temperature alloys limit their processing, especially for parts with complex shapes. The processing is difficult, the workpiece is easy to deform, it is difficult to ensure accuracy, and it takes more time and resources.
Recently, a German customer asked Moresuperhard for ceramic inserts, hoping to improve the current processing situation. The common alumina ceramic inserts he used include RCGX 090700 T01020, RCGX 120700 T01020, etc. However, these inserts are not suitable for processing common nickel-based high-temperature alloys such as Inconel 718, Rene 65, and Udimet 720 alloys. When processing high-temperature alloys, if the wrong ceramic tool is selected, the following situations will easily occur: groove wear, cutting-edge deformation, tool chipping, and tool peeling.
Moresuperhard's professional engineers recommend that the following two types of ceramic inserts be selected for nickel-based alloy processing:
1. Whisker-reinforced ceramic inserts: suitable for processing forging blanks with rough and hard skin and ovality, with better toughness and overall strength, suitable for rough processing under harsh conditions.
2. Sialon ceramic inserts: a mixture of silicon nitride and alumina, suitable for heavy load rough processing, plunge cutting, and direct milling of workpiece corners. Compared with whisker-reinforced ceramics, the cutting speed of Sialon ceramic inserts can be increased by about 20%, and the metal removal rate is significantly higher than that of whisker-reinforced ceramic inserts.
After communicating with the customer about Moresuperhard's previous related cases and solutions, the customer decided to try the whisker ceramic tools recommended by Moresuperhard.
1. Improve processing efficiency, achieve higher output and shorter cycle time
2. Improve toughness and fracture resistance, increase feed rate
3. Provide a variety of sharp-edge treatments
4. Efficient cutting, extended tool life
5. Suitable for continuous cutting, with superior performance
6. Can be used for dry and wet processing, suitable for heavy interrupted cutting
1. Coolant close to the cutting area: Keep the coolant as close to the cutting area as possible to improve productivity and tool life.
2. Use round ceramic inserts: In most applications, round ceramic inserts can achieve higher productivity and tool life.
3. Avoid notch wear: The most common wear is notch when turning high-temperature alloys. To avoid this phenomenon, it is recommended that the cutting depth does not have to be consistent.
4. Alternating cutting method: The traditional straight-line constant back-cutting method is adjusted to alternate between oblique variable back-cutting and straight-line constant back-cutting.
Please communicate with us if you have more experience and ideas about machining high-temperature alloys. If you are worried about choosing cutting tools for high-temperature alloy machining, please learn about Moresuperhard's tools.
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