Machining of Precision Superalloy Parts
Superalloy is a kind of engineering material used at about 1000 °C. It is widely used in aerospace, aviation and various heat treatment equipment. Since the high-temperature alloy contains many high-melting alloying elements such as Fe, Ti, Cr, Ni, V, W, Mo, etc., these alloying elements and other alloying elements constitute a high-purity, densely organized austenitic alloy. Moreover, some elements and non-metallic elements such as C, B, N constitute metal and non-metallic compounds with high hardness, low specific gravity and high melting point, which make their machinability very poor. Its relative machinability is only 5-20% of 45 steel.
Cutting characteristics
a, large cutting force: It is 2 to 3 times larger than cutting 45 steel.
b, high cutting temperature: It is about 50% higher than cutting 45 steel.
C. Work hardening is serious: The hardness of the machined surface and the machined surface when cutting it is 50 to 100% higher than that of the substrate.
d, Tools are easy to wear: Easy to bond, diffuse, oxidize and groove wear during cutting.
Tool material
a, high speed steel: High vanadium, high carbon, aluminum-containing high speed steel should be used.
b, cemented carbide: YG type cemented carbide should be used. It is preferable to use fine particles containing TaC or NbC and ultrafine particle cemented carbide. Such as YG8, YG6X, YG10H, YW4, YD15, YGRM, YS2, 643, 813, 712, 726 and so on.
c, ceramic: In the machining of cast superalloy, the ceramic tool has its unique advantages.
Tool geometric parameters
Deformed superalloys (such as forging, hot rolling, cold drawing). The tool rake angle γ0 is about 10°; Cast superalloy gamma 0 is about 0°, generally without negative chamfering. The back angle of the tool is generally α=10°～15°. The rake angle λs during roughing is -5° to -10°, and λs = 0 to 3° during finishing. The principal deviation angle kappa R is 45° to 75°. The radius of the tool tip arc is 0.5-2 mm. and a large value is taken during roughing.
Cutting amount
a, high speed steel cutter: Cutting speed of casting superalloy is about 3 m/min, and cutting deformation superalloy Vc is 5-10 m/min.
b. Carbide tools:
Cutting deformation superalloy Vc: 40 ~ 60m / min; Cutting casting superalloy Vc = 7-10m/min. Both the feed amount f and the depth of cut αp should be greater than 0.1 mm. In order to avoid the cutting of the tool on the hardened surface, the tool wear is aggravated.
Cutting fluid
For roughing, emulsion and extreme pressure emulsion are used. For finishing, extreme pressure emulsion or extreme pressure cutting oil is used. When reaming, use vulcanized oil 85 ~ 90% + kerosene 10 ~ 15%, or sulfurized oil (or lard) + CCl4. High temperature alloy tapping is very difficult. In addition to properly increasing the diameter of the bottom hole, white lead oil + mechanical oil, or chlorinated paraffin should be diluted with kerosene, or MoS2 grease should be used.
Superalloy drilling
Drilling of superalloys is very difficult. Generally, carbide drills, such as shallow hole drills, solid or inlaid carbide drills, should be used. If a high speed steel drill bit is used, the secondary back angle α'0 of the drill bit should be ground to reduce the friction with the hole wall. At the same time, the drill tip should be ground to reduce the width of the chisel edge to reduce the axial force during drilling. The drill bit should be sharp, and it is best to use automatic feed. When drilling, the drill should not stay on the cutting surface, so as not to aggravate the hardening of the cutting surface, which will bring difficulties to the next feeding.
Cutting characteristics
a, large cutting force: It is 2 to 3 times larger than cutting 45 steel.
b, high cutting temperature: It is about 50% higher than cutting 45 steel.
C. Work hardening is serious: The hardness of the machined surface and the machined surface when cutting it is 50 to 100% higher than that of the substrate.
d, Tools are easy to wear: Easy to bond, diffuse, oxidize and groove wear during cutting.
Tool material
a, high speed steel: High vanadium, high carbon, aluminum-containing high speed steel should be used.
b, cemented carbide: YG type cemented carbide should be used. It is preferable to use fine particles containing TaC or NbC and ultrafine particle cemented carbide. Such as YG8, YG6X, YG10H, YW4, YD15, YGRM, YS2, 643, 813, 712, 726 and so on.
c, ceramic: In the machining of cast superalloy, the ceramic tool has its unique advantages.
Tool geometric parameters
Deformed superalloys (such as forging, hot rolling, cold drawing). The tool rake angle γ0 is about 10°; Cast superalloy gamma 0 is about 0°, generally without negative chamfering. The back angle of the tool is generally α=10°～15°. The rake angle λs during roughing is -5° to -10°, and λs = 0 to 3° during finishing. The principal deviation angle kappa R is 45° to 75°. The radius of the tool tip arc is 0.5-2 mm. and a large value is taken during roughing.
Cutting amount
a, high speed steel cutter: Cutting speed of casting superalloy is about 3 m/min, and cutting deformation superalloy Vc is 5-10 m/min.
b. Carbide tools:
Cutting deformation superalloy Vc: 40 ~ 60m / min; Cutting casting superalloy Vc = 7-10m/min. Both the feed amount f and the depth of cut αp should be greater than 0.1 mm. In order to avoid the cutting of the tool on the hardened surface, the tool wear is aggravated.
Cutting fluid
For roughing, emulsion and extreme pressure emulsion are used. For finishing, extreme pressure emulsion or extreme pressure cutting oil is used. When reaming, use vulcanized oil 85 ~ 90% + kerosene 10 ~ 15%, or sulfurized oil (or lard) + CCl4. High temperature alloy tapping is very difficult. In addition to properly increasing the diameter of the bottom hole, white lead oil + mechanical oil, or chlorinated paraffin should be diluted with kerosene, or MoS2 grease should be used.
Superalloy drilling
Drilling of superalloys is very difficult. Generally, carbide drills, such as shallow hole drills, solid or inlaid carbide drills, should be used. If a high speed steel drill bit is used, the secondary back angle α'0 of the drill bit should be ground to reduce the friction with the hole wall. At the same time, the drill tip should be ground to reduce the width of the chisel edge to reduce the axial force during drilling. The drill bit should be sharp, and it is best to use automatic feed. When drilling, the drill should not stay on the cutting surface, so as not to aggravate the hardening of the cutting surface, which will bring difficulties to the next feeding.
