Types, properties, characteristics, and applications of cemented carbide inserts

Carbide inserts, especially indexable carbide inserts, are the leading products of CNC machining tools. Since the 1980s, various types of integral and indexable carbide inserts or inserts have been expanded to various cutting tool fields, among which indexable carbide inserts have expanded from simple turning and surface milling cutters to various precision, complex, and shaped tool fields.

(1) Types of cemented carbide inserts

   According to the main chemical composition, cemented carbide can be divided into tungsten carbide based cemented carbide and titanium carbide (TiC (N)) based cemented carbide.

Tungsten carbide based cemented carbides include three types: tungsten cobalt (YG), tungsten cobalt titanium (YT), and rare carbide (YW). Each has its advantages and disadvantages. The main components are tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC), and niobium carbide (NbC). The commonly used metal bonding phase is Co.

Titanium carbide (nitride) based cemented carbides are cemented carbides with TiC as the main component (some with other carbides or nitrides added). The commonly used metal bonding phases are Mo and Ni.

ISO (International Organization for Standardization) classifies cutting cemented carbides into three categories:

Class K, including Kl0 to K40, is equivalent to the YG class in China (mainly composed of WC. Co).

Category P, including P01 to P50, is equivalent to Category YT in China (mainly composed of WC. TiC. Co).

Category M, including M10 to M40, is equivalent to the YW category in China (mainly composed of WC-TiC-TaC (NbC) - Co).

Each brand represents a series of alloys ranging from high hardness to Z large toughness with numbers ranging from 01 to 50.

(2) Performance characteristics of cemented carbide inserts

The performance characteristics of cemented carbide inserts are as follows:

① High hardness: The cemented carbide blade is made of carbide (called hard phase) and metal binder (called adhesive phase) with high hardness and melting point by powder metallurgy method. Its hardness reaches 89 to 93HRA, which is much higher than that of high-speed steel. At 5400C, the hardness can still reach 82 to 87HRA, which is the same as that of high-speed steel at room temperature (83 to 86HRA). The hardness value of cemented carbide varies with the nature, quantity, particle size, and content of the metal bonding phase of the carbide, and generally decreases with the increase of the content of the bonding metal phase. When the content of adhesive phase is the same, the hardness of YT type alloys is higher than that of YG type alloys, and alloys added with TaC (NbC) have higher high-temperature hardness.

② Bending strength and toughness: The bending strength of commonly used cemented carbides ranges from 900 to 1500MPa. The higher the content of metal bonding phase, the higher the bending strength. When the adhesive content is the same, the strength of YG type (WC-Co) alloys is higher than that of YT type (WC-TiC-Co) alloys, and the strength decreases with the increase of TiC content. Cemented carbide is a brittle material whose impact toughness at room temperature is only 1/30 to 1/8 that of high-speed steel.

(3) Application of commonly used cemented carbide inserts

   YG type alloys are mainly used for processing cast iron, nonferrous metals, and non-metallic materials. Fine grain cemented carbides (such as YG3X, YG6X) have higher hardness and wear resistance than medium grain cemented carbides when their cobalt content is the same. They are suitable for processing some special hard cast iron, austenitic stainless steel, heat resistant alloys, titanium alloys, hard bronze, and wear-resistant insulating materials.

   The outstanding advantages of YT cemented carbide are high hardness, good heat resistance, higher hardness and compressive strength at high temperatures than YG cemented carbide, and good oxidation resistance. Therefore, when a knife is required to have high heat resistance and wear resistance, a brand with a high TiC content should be selected. YT alloys are suitable for processing plastic materials such as steel, but are not suitable for processing titanium alloys or silicon aluminum alloys.

   YW type alloys have both the properties of YG and YT type alloys, with good comprehensive properties. They can be used not only for processing steel, but also for processing cast iron and nonferrous metals. This type of alloy can have high strength if the cobalt content is appropriately increased, and can be used for rough machining and intermittent cutting of various difficult to process materials.