Superalloy is also called heat-resistant alloy in mechanical processing. Because of its good high temperature strength, thermal stability and fatigue resistance, it can work in high temperature oxidation atmosphere or gas conditions, and has been widely used. Superalloy cutting performance is poor, mainly in plastic deformation, cutting force, high cutting temperature, severe cold hardening phenomenon, tool is easy to produce bonding, diffusion, boundary and groove wear. Here we will introduce how to turn superalloy in mechanical processing.
1. Superalloy Turning Tools
Turning superalloy with ordinary high speed steel has low tool durability. If high vanadium, high carbon, aluminium and cobalt high speed steels are used, the tool durability will be higher. Cemented carbide is the main tool material for turning superalloy. YG cemented carbide with fine or superfine particles should be selected.
The rake angle of cemented carbide cutter is generally about 10 degrees, and it is 0-5 degrees when finishing. Because the machinability of casting superalloy is worse, the rake angle should be smaller, about 0 degrees. The form of rake face is linear arc and circular arc. In order to have better chip breaking effect. The working hardening of superalloys is serious. It is necessary to keep the blade sharp and not allow sawtooth and other defects. Generally, negative chamfering is not grinded out. If it is to be grinded out, it is smaller than that of cutting general steel.
2. Cutting parameters
Turning superalloy also has cutting speed corresponding to the optimum cutting temperature. The cutting speed of superalloy with carbide turning tool is (10-60) m/min. Cast superalloys adopt lower cutting speed and deformed superalloys adopt higher cutting speed. The cutting depth is (3-7) mm in rough turning and (0.2-0.5) mm in finish turning. In order to avoid cutting on hardened layer, the feed should be greater than 0.1mm/r.
3. Cutting fluid
When turning superalloy, cutting fluid should be used, which can reduce the cutting temperature by about 25%. Water solution should be used for high-speed steel cutting tools and emulsified or extreme pressure cutting oil should be used for carbide cutting tools. Sulfur-containing extreme pressure cutting fluid should not be used for nickel-based superalloys in order to avoid stress corrosion and reduce fatigue strength.
4. Issues to be noted
In order to avoid cutting on hardened layer, the cutting depth should be greater than 0.2 mm and the feed rate should be greater than 0.1 mm/r. In order to keep sharp edge and reduce the hardening phenomenon, the standard of tool grinding bluntness should be less than 0.2 mm. When cutting high-speed steel tools, it is necessary to avoid the tool staying on the cutting surface in order to prevent the hardening of the cutting surface from aggravating and bring difficulties to the next cutting tool.
