Part 4: Classification and application fields of cemented carbide
Chapter 11 Carbide Cutting Tools and Processing
11.0 Carbide Cutting Tools and Processing
11.0.1 What is cutting?
Cutting is a core process in machining, which is a process of using tools to cut off excess parts from the workpiece material to obtain the desired shape, size and surface quality. Cutting relies on the sharpness of the tool and the plastic or brittle deformation of the material, and gradually removes the material layer by using forces such as shear, extrusion and friction. The cutting process usually involves high-speed rotation or feed motion, which produces chips and exhibits different physical properties in metal cutting (such as steel, cast iron) or non-metal cutting (such as composite materials). The efficiency and quality of cutting are directly affected by the tool material, geometric parameters, cutting parameters (such as speed, feed rate, depth of cut) and the hardness and toughness of the workpiece material. As a key tool in cutting processing, cemented carbide cutting tools have significantly improved cutting accuracy, efficiency and tool life with their excellent performance, and have become an indispensable part of modern manufacturing.
1.0.2 What are carbide cutting tools?
Cemented carbide cutting tools are cutting tools made of cemented carbide as the base material. They are widely used in metal cutting, non-metallic processing, and composite material processing. With their excellent mechanical properties and durability, they have become an indispensable core equipment in modern manufacturing. Cemented carbide is a composite material made of carbide (such as tungsten carbide WC, titanium carbide TiC , tantalum carbide TaC ) as a hard phase and metal (such as cobalt Co, nickel Ni) as a bonding phase through advanced powder metallurgy processes (including mixing, pressing, sintering and post-processing). Its preparation process involves precise proportioning of high-purity raw materials, high-temperature sintering (1400-1600°C) under vacuum or inert atmosphere, and precision machining or coating treatment to ensure material uniformity and performance stability. Its excellent performance is mainly reflected in the following key aspects:
Excellent performance of cemented carbide cutting tools – high hardness
The hardness range is HV 1600-2500 (±30), which is much higher than traditional high-speed steel (HV 800-900) or tool steel (HV 600-700). This feature enables it to effectively cut a variety of high-hardness materials, including steels (such as carbon steel Q235 HV 150-250±10, alloy steel 40Cr HV 200-400±10), cast irons (such as gray cast iron HT200 HV 150-220±10, ductile iron QT500 HV 200-250±10), as well as difficult-to-machine materials (such as titanium alloy TC4 HV 300-400±10, nickel-based alloy Inconel 718 HV 400-500±10) and superhard materials ( such as polycrystalline diamond PCD HV >5000±50). This high hardness maintains cutting edge stability during high-speed cutting, avoids geometric misalignment due to wear, and significantly extends tool life (up to hundreds of hours under suitable working conditions), making it particularly suitable for high-precision and continuous cutting tasks.
Excellent performance of cemented carbide cutting tools – excellent toughness
The fracture toughness ( K₁c ) is 10-20 MPa·m¹ / ² ( ±0.5), and a dynamic balance between hardness and toughness is achieved by adjusting the cobalt content of the binder phase ( usually 6 %-20%) or adding trace rare earth elements (such as Ce, La). This toughness property enables it to withstand high-frequency impact, vibration and thermal stress during the cutting process, especially in intermittent cutting (such as machining cast iron or workpieces with gaps), heavy-load machining (such as deep hole drilling) or intermittent loading conditions. In addition, by optimizing the grain size (0.5-2 μm ) or introducing nano-scale carbides, the material’s resistance to crack propagation is further improved, ensuring the structural integrity of the tool under complex working conditions.
Excellent performance of cemented carbide cutting tools – wear resistance
The wear rate is less than 0.05 mm³ / N · m ( ±0.01 mm³ / N · m ) . Thanks to the high hardness of carbides and the lubrication of the binder phase, the tool can maintain its cutting performance after long-term cutting (lifespan >10 hours±1 hour, up to 50-100 hours depending on the working conditions). Especially under conditions of high speed (1000-2000 m/min±10 m/min) or containing hard particles (such as grinding wheel abrasives, ceramic powder), cemented carbide tools show excellent wear resistance. This wear resistance comes from the synergistic effect of the dense structure inside the material (density >98% theoretical value) and the surface coating (such as TiN , Al₂O₃ , TiAlN , thickness 5-25 μm ), and is widely used in high-load processing scenarios such as high-speed milling, drilling and turning .
Excellent performance of cemented carbide cutting tools – other performance advantages
In addition to the above core characteristics, cemented carbide cutting tools also have excellent resistance to high-temperature oxidation (resistant to 800-1000°C), low thermal expansion coefficient (about 4.5-6.0×10 ⁻ ⁶ /°C), and good chemical stability (acid and alkali corrosion resistance). These characteristics enable it to adapt to a variety of processing environments from room temperature to high temperature (300-800°C), and are particularly suitable for aerospace (such as titanium alloy processing), energy industry (such as high-temperature alloy blades) and electronics industry (such as high-precision micromachining). In addition, through modern manufacturing technologies (such as hot isostatic pressing HIP and laser surface treatment), the internal defects of the tool (such as pores and cracks) are effectively reduced, further improving its service life and reliability.
Application and development of cemented carbide cutting tools
The application range of cemented carbide cutting tools covers a variety of workpieces such as steel, cast iron, difficult-to-process materials, non-ferrous metals, composite materials and superhard materials. They are widely used in automobile manufacturing (such as engine parts), aerospace (such as turbine discs), mold processing (such as stamping dies) and electronics industry (such as circuit board drilling). With the advancement of Industry 4.0 and intelligent manufacturing, cemented carbide tools are moving towards high performance (such as nano coatings, gradient materials) and intelligence, such as integrated sensors to monitor wear status or optimize cutting parameters through AI to meet higher efficiency and more complex needs.
11.0.3 What are the cemented carbide cutting tools?
Carbide cutting tools are cutting tools made of cemented carbide as the base material. With their excellent hardness, wear resistance and toughness, they are widely used in metal cutting and non-metal processing. These tools meet the diverse needs from general processing to high-precision and complex working conditions through precision design, advanced surface treatment processes and geometric optimization. The following are the main types of carbide cutting tools and their characteristics, application scenarios and optimization technologies, which are comprehensively and detailedly explained in combination with industry practices and the latest technological developments.
(1) Carbide turning tools
are the core tools in lathe processing. Through the rotation of the workpiece and the axial or radial feeding of the tool, the cutting of the outer circle, inner hole, end face, step, thread and complex contour is completed. Carbide turning tools are usually made of high-hardness materials (such as YG6, YG8, YT15, YT30). The tool body includes solid carbide, welded carbide blades or replaceable blade structures to meet different processing requirements. The tool rake angle (5°-15°±0.5°) and back angle (6°-12°) are precisely geometrically optimized to reduce cutting force and chip resistance and improve cutting efficiency; the secondary back angle (1°-3°) and cutting edge chamfer (0.1-0.2 mm) further enhance the ability to resist chipping . Surface coating technology is widely used, such as PVD coating ( TiN , TiCN , thickness 2-5 μm ) and CVD coating ( Al₂O₃ , TiAlN , thickness 5-25 μm±0.1 μm ) , which significantly improves heat resistance (up to 1000°C), wear resistance and oxidation resistance. During the cutting process, the turning tool needs to withstand the stable load of continuous cutting or the impact of intermittent cutting. The service life is generally 10-20 hours (±1 hour), and the accuracy can reach <0.01 mm (±0.001 mm), which is suitable for high-precision parts processing. Its technical characteristics include cutting speed 100-500 m/min (±10 m/min), hardness HV 1800-2200, fracture toughness 12-18 MPa·m ¹ / ² , wear rate <0.05 mm ³ / N · m . It is widely used in the automotive industry to process crankshafts, camshafts and connecting rods, mold manufacturing precision turning mold cavities and stamping dies, and aviation parts processing titanium alloy outer circles and aluminum alloy parts.
(2) Carbide milling cutters: Milling cutters are used for high-speed cutting with multiple
blades on a milling machine . They are suitable for machining planes, slots, steps, sides and complex curved surfaces. They are the core tools of multi-axis machining centers. Carbide milling cutters include end mills, face mills, ball-end mills and profile mills. Commonly used grades include YG10 (high toughness, suitable for intermittent cutting), YT30 (high heat resistance, suitable for high temperature conditions) and YW2 (excellent overall performance). End mills are mostly solid carbide structures with 2-4 blades and a diameter of 3-20 mm. They are suitable for small-diameter holes and slots and fine machining. Face mills have larger diameters (50-200 mm) and use replaceable blades or integral designs. They have 4-12 blades and are suitable for large-area plane milling. Ball-end mills and profile mills are used for complex curved surfaces and mold machining. Geometric optimization includes helix angle (30°-45°±1°) to improve chip discharge, positive rake angle (5°-10°) to reduce cutting force, and R angle (0.5-2 mm) to enhance edge strength. CVD coating (such as TiAlN , Al₂O₃ , thickness 10-25 μm ) or PVD coating (such as CrN , thickness 2-5 μm ) provides temperature resistance (up to 1100°C) and wear protection. Cutting speed 200-1000 m/min, life 5-15 hours, accuracy <0.02 mm, its technical characteristics are hardness HV 1700-2100, fracture toughness 14-20 MPa·m ¹ / ² , strong impact resistance, the main application scenarios include aerospace processing of aluminum alloy skins and titanium alloy components, mold industry milling of complex surfaces and stamping dies, and machining of slot parts and gear profiles.
(3) Carbide drills
Carbide drills are used for drilling, replacing traditional high-speed steel drills, and are suitable for drilling deep holes, small diameter holes, and multi-layer materials. Twist drills are general-purpose, using YG6X (nanocrystalline structure , hardness HV 1900-2000), with a helix angle of 25°-35°±1°, and can drill holes with a diameter of 5-50 mm, suitable for general-purpose drilling; deep hole drills (such as gun drills) use YW1, with a length-to-diameter ratio of up to 100:1, equipped with internal cooling channels to reduce heat accumulation and chip removal, suitable for deep hole processing (such as >100 mm); step drills use a multi-layer blade design, which can process step holes of different diameters at one time, and are widely used in molds and mechanical parts. PVD coating (such as TiN , TiCN , thickness 10-15 μm ) or CVD coating (diamond, thickness 5-10 μm ) enhances wear resistance and high temperature resistance, cutting speed 50-300 m/min, life 10-30 hours, precision <0.01 mm. Its technical characteristics include hardness HV 1800-2200, wear resistance <0.03 mm³ / N · m , good high temperature resistance (up to 900°C), widely used in automotive parts drilling (such as cylinder blocks, connecting rods), electronic component PCB board processing, and deep hole drilling of aviation structural parts (such as wing joints). The key to optimization is to add self-lubricating coating (such as MoS₂ ) to reduce friction and optimize the chip groove design to prevent clogging.
(4) Carbide Boring Tools
Boring tools are used to expand or fine-tune existing hole diameters. Carbide boring tools are mostly adjustable, integral or replaceable. Rough boring tools use YG8 (high toughness, HV 1700-1900), with a cutting depth of 1-5 mm, suitable for rapid roughing, and a tool diameter range of 20-150 mm; fine boring tools use YT5 (hardness HV 1750-1850), with a cutting depth of 0.1-0.5 mm and an accuracy of <0.005 mm, suitable for high-precision hole processing. The tool geometry includes a rake angle of 5°-10° (negative rake angle can be used for rough boring), a secondary back angle of 2°-5° and a cutting edge relaxation angle (0.2°-0.5°). CVD coating (such as Al₂O₃ , thickness 10-20 μm ) or PVD coating (such as TiAlN ) enhances heat resistance and surface finish. The cutting speed is 100-400 m/min, the service life is 15-25 hours, and the technical characteristics are fracture toughness of 12-16 MPa·m ¹ / ² and surface roughness Ra <0.4 μm . The main application scenarios include engine cylinder block fine boring (cylinder diameter accuracy <0.01 mm), hydraulic parts internal hole processing (such as pump body), and mold precision boring (such as punching die).
(5) Carbide reamers (Reamers)
Reamers are used for finishing the hole diameter, improving the roundness, tolerance and surface finish, and are suitable for mass production and high-precision requirements. Machine reamers use YG6 (hardness HV 1800-2000), with a diameter range of 5-50 mm, 4-8 blades, and a blade length of 1.5-2 times the diameter; adjustable reamers use YT15 , with an adjustment range of ±0.02 mm, which is suitable for fine-tuning the hole diameter and multi-specification processing. The geometric design includes straight or spiral blades (helix angle 5°-10°), rake angle 5°-8°, PVD coating (such as TiCN , thickness 10-15 μm ) or CVD coating (such as Al ₂ O ₃ ) to improve wear resistance and anti-sticking. Cutting speed 20-100 m/min, life 20-40 hours, accuracy <0.002 mm, its technical characteristics include hardness HV 1800-2100, wear resistance <0.02 mm³ / N · m , widely used in bearing hole finishing (roundness <0.005 mm), automobile transmission shaft holes, and precision instrument parts (such as measuring tool holes).
(6) Carbide broaches :
Broaches are used for broaching and are suitable for mass production of keyways, tooth shapes, racks and complex contours. Circular broaches use YW2 (strong heat resistance, HV 1750-2000), with a diameter of 10-100 mm, 10-20 teeth, and progressive tooth height (0.1-0.5 mm/tooth); flat broaches use YG10, with a width of 20-100 mm and 15-30 teeth, suitable for plane broaching. Geometric optimization includes rake angle of 5°-10°, chip groove depth of 2-5 mm, CVD coating (such as TiAlN , thickness of 15-20 μm ) or PVD coating (such as CrN ) to enhance impact resistance and heat resistance. The cutting speed is 10-50 m/min, the service life is 10-20 hours, and the accuracy is <0.01 mm. Its technical characteristics are fracture toughness of 14-18 MPa·m ¹ / ² and excellent impact resistance. The main application scenarios include gear keyway broaching (module 1-5), aviation structural parts tooth drawing (such as fuselage connectors), and mold drawing (such as punching dies).
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