The tool plays a leading role in the metal cutting process. Tool geometric parameters and cutting dosage are based on the performance of the tool material. Especially in the cutting of high-temperature alloys, optimizing the tool material is often the first task of the craftsman. For this reason, every machining craftsman must understand the performance of the tool material. According to the characteristics of high-temperature alloy cutting, the following properties should be given priority in the selection of tool materials:
Cutting temperature is a key issue in superalloy cutting. As the temperature of any tool material increases, its hardness and strength will decrease. The key to the problem is the speed of the decrease and the maximum heat-resistant temperature of the cutting tool material. The heat resistance of high-speed steel generally does not exceed 650°C, the heat resistance of cemented carbide is 800-1000°C, and the heat resistance of ceramic tools can reach 1200°C. There is a considerable difference in heat resistance between various grades of high-speed steel and cemented carbide. Therefore, in the processing of high-temperature alloys, good heat resistance must first be considered when selecting tool materials.
2. High hardness and wear resistance
During processing, the hard surface of the high-temperature alloy (including the work-hardened layer) or the mixed hard points will cause severe friction with the tool, which requires the tool material to have high hardness and wear resistance. The hardness should not only consider the normal temperature hardness, but also the high temperature hardness. In addition to being related to hardness, wear resistance is also related to the material’s chemical stability (including oxidation resistance), anti-adhesion ability, etc., that is, it is related to the chemical composition, metallographic structure, grain size and other factors of the tool.
The author of this book and others have discovered that GH2135 alloy often forms point-like segregation due to too high melting rate during electroslag smelting. It is a gathering area of TiC and M3B2 phases. The grains in the area are fine and the hardness is higher than that of the non-point-like area. When turning the GH2135 turbine disc, the phenomenon of “cutting” often occurs.
3. Sufficient strength and toughness
The cutting force is large when cutting high-temperature alloys, and sometimes the cutting force fluctuates greatly. This requires the tool material to have sufficient strength and toughness to withstand it.
Performance 2 and performance 3 are often contradictory for a tool material, and it is difficult to balance them at the same time. They should be emphasized based on the different characteristics of various high-temperature alloy processing and should be considered comprehensively. When selecting tool materials suitable for processing high-temperature alloys, in addition to cutting force and cutting temperature, you must also consider the following issues:
(1) Affinity between materials. The affinity between certain elements of the workpiece material and the elements of the tool material often aggravates tool wear. Therefore, care must be taken when selecting tool materials. For example, the titanium element in high-temperature alloys and titanium carbide in cemented carbide are compatible with each other. Therefore, it is not suitable to use titanium carbide-based carbide tools to process titanium-containing high-temperature alloys. The carbon element of diamond has an affinity with iron, so diamond tools are not suitable for processing iron-based high-temperature alloys.
(2) In high-temperature alloy processing, the so-called “optimal cutting speed” exists in a large number of situations, that is, at a certain cutting speed, the tool wear is the smallest, the durability is the highest, and the cutting distance is the longest. The optimal cutting speed value varies with tool material, workpiece material and other cutting conditions. For this reason, when the cutting conditions such as the workpiece material are known, the best way to select the carbide (or other cutting tool material) tool grade is to first find the optimal cutting speed of each grade and its corresponding durability (or cutting distance), and then comprehensively consider it to select a tool brand that is both economical and efficient.
(3) Various tool materials (such as high-speed steel, cemented carbide, ceramics, cubic boron nitride, diamond, etc.) adapt to different cutting speed ranges. Their respective advantages can only be fully demonstrated within the corresponding speed range. Materials such as ceramics and cubic boron nitride require high cutting speeds. Taking advantage of their good chemical stability in high-temperature areas, high cutting temperatures soften the surface layer of the material being processed, widening the hardness and strength gap between the tool and the workpiece to facilitate cutting. High-speed steel requires low cutting speed. For example: Nickel-based high-temperature alloys are difficult to process. If high-speed steel is used for processing, its durability and processing quality are not bad, but the cutting speed is required to be lower than 10m/min. However, if it is processed with cubic boron nitride tools, the best cutting The speed range is 120-150m/min. Of course, high-speed steel cannot bear such a high cutting speed. On the contrary, if cubic boron nitride is used at low speeds, the tool durability is no better than high-speed steel.
Tianjin Anton Metal Manufacture Co., Ltd. is a company specializing in the production of various nickel-based alloys, Hastelloy alloys and high-temperature alloy materials. The company was established in 2001 with a registered capital of 16.8 million, specializing in the production and sales of alloy materials. Anton Metal’s products are widely used in aerospace, chemical industry, electric power, automobile, nuclear energy and other fields, and can also provide customized alloy material solutions according to customer needs. If you need to know the price consultation of alloy materials or provide customized alloy material solutions, please feel free to contact the sales staff.
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Post time: Sep-02-2023
