Superalloys are also known as heat-resistant alloys in machining. Because it has good high temperature strength, thermal stability and fatigue resistance, it can work in high temperature oxidizing atmosphere or gas conditions, and is widely used. The machining performance of superalloys is poor, mainly in the large plastic deformation, large cutting force, high cutting temperature, and serious chilling phenomenon. The tool is prone to bonding, diffusion, boundary and groove wear. Let's go into details. Introduce how to turn superalloys in machining.
1. High temperature alloy turning tools
When turning superalloys with ordinary high-speed steel, the tool durability is very low. If high vanadium, high carbon, aluminum and cobalt containing high speed steel is used, the tool durability will be higher. Carbide is the main tool material for turning superalloys. YG-type cemented carbide with fine particles or ultra-fine particles should be selected. The rake angle of the carbide tool is generally about 10°, and it is 0°-5° during fine turning. Due to the poor machinability of cast superalloys, the rake angle should be smaller, around 0°. The rake face forms are mostly straight arcs and arcs. In order to have better chip breaking effect. The superalloy has serious work hardening, and the blade must be kept sharp, and no defects such as serrations are allowed. Generally, the negative chamfers are not ground.
2. Cutting amount
Turning superalloys also has cutting speeds that correspond to optimum cutting temperatures. The cutting speed of cutting superalloy with cemented carbide turning tool is (10-60) m/min. Cast superalloys use lower cutting speeds, and deformed superalloys use higher cutting speeds. The cutting depth is (3-7) mm during rough turning and (0.2-0.5) mm during fine turning. In order to avoid cutting on the hardened layer, the feed rate should be greater than 0.1mm/r.
3. Cutting fluid
When turning superalloys, cutting fluid should be used, which can reduce the cutting temperature by about 25%. Aqueous solution should be used for high-speed steel tools, and emulsion or extreme pressure cutting oil should be used for cemented carbide tools. Sulfur-containing extreme pressure cutting fluids should not be used for nickel-based superalloys to avoid stress corrosion and reduce fatigue strength.
4. Issues that should be paid attention to
Generally, cemented carbide should be used to turn superalloys as much as possible. Pay attention to the quality of tool sharpening, so that the surface roughness of each blade surface is less than 0.4μm, and the blade must not have serrations and other defects; in order to avoid cutting on the hardened layer, the cutting depth should be If it is greater than 0.2mm, the feed rate should be greater than 0.1mm/r; in order to keep the blade sharp and reduce the phenomenon of work hardening, the tool blunt standard should be less than 0.2mm; when using high-speed steel tools for cutting, the tool should be avoided to stay on the cutting surface to avoid The anti-cut surface hardening increases, making the next pass difficult.