Diamond Polishing Tools

The Difference Between Diamond Tools and Tungsten Steel Tools

The Difference Between Diamond Tools and Tungsten Steel Tools

  • Friday, 10 November 2023
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The advanced processing device and the high-efficiency CNC tool can give full play to its effect and obtain good economic benefits. Because the tool is subjected to high pressure, high temperature, friction, shock, and vibration when cutting. Material is an important factor affecting the cutting ability of a tool and also has a considerable impact on processing efficiency, processing quality, processing cost, and tool durability.

The Tool Material Should Have Basic Performance

With the rapid development of tool materials, the physical, mechanical, and cutting performance of various new tool materials have been greatly improved, and the scope of application has been continuously expanded. The choice of tool material has a great influence on tool life, machining efficiency, machining quality, and machining cost. Cutting tools are subject to high pressure, high temperature, friction, shock, and vibration. Therefore, the tool material should have the following basic performance:

For hardness and wear resistance, the hardness of the tool material must be higher than that of the workpiece material, generally above 60HRC. The higher the hardness of the tool material, the better the wear resistance.

Strength and toughness, the tool material should have high strength and toughness to withstand cutting force, impact, and vibration, and prevent brittle fracture and chipping of the tool.

Heat resistance, the heat resistance of the tool material is better, it can withstand high cutting temperatures and has good oxidation resistance.

In terms of process efficiency and economy, the tool material should have good forging efficiency, heat treatment efficiency, welding efficiency, grinding efficiency, etc., and a high performance-price ratio should be pursued.

Introduction to Diamond Tools and High-Speed Steel Cutting (Tungsten Steel) Tools

Diamond Tool
Diamond is an allotrope of carbon, the hardest material that has been found in nature. Diamond tools have high hardness, high wear resistance, and high thermal conductivity, and are widely used in the processing of non-ferrous and non-metallic materials. Especially in the high-speed cutting of aluminum and silicon-aluminum alloys, diamond tools are the main cutting tool varieties that are difficult to replace. Diamond tools that can achieve high efficiency, high stability and long life are an indispensable tool in modern CNC machining.

Types of Diamond Tools
Natural diamond tool:
Natural diamond has been used as a cutting tool for hundreds of years. After fine grinding, the natural single-crystal diamond tool can be sharpened very sharply. The workpiece accuracy and extremely low surface roughness are recognized, ideal and irreplaceable ultra-precision machining tools.

PCD diamond tools:
Natural diamond is expensive, and polycrystalline diamond (PCD) is widely used in cutting. Since the early 1970s, polycrystalline diamond (Polycrystauine Diamond) prepared by high-temperature and high-pressure synthesis technology, referred to as PCD blades, has been successfully developed. In many cases, natural diamond tools have been replaced by synthetic polycrystalline diamond. PCD is rich in raw materials, and its price is only one-tenth of that of natural diamonds.

PCD tools cannot grind extremely sharp edges, and the surface quality of the processed workpieces is not as good as that of natural diamonds. At present, PCD inserts with chip breakers cannot be easily manufactured in the industry. Therefore, PCD can only be used for fine cutting of non-ferrous metals and non-metals, and it is difficult to achieve ultra-precision mirror cutting.

CVD diamond tools:
CVD diamond technology has been around in Japan since the late 1970s and early 1980s. CVD diamond refers to the synthesis of a diamond film on a heterogeneous substrate (such as cemented carbide, ceramics, etc.) by chemical vapor deposition (CVD). CVD diamond has the exact same structure and characteristics as natural diamond.

The performance of CVD diamonds is very close to that of natural diamonds. It has the advantages of natural single-crystal diamond and polycrystalline diamond (PCD), and overcomes their shortcomings to a certain extent.

Characteristics of Diamond Tools
Extremely high hardness and wear resistance:
Natural diamond is the hardest substance that has been found in nature. Diamond has extremely high wear resistance. When machining high-hardness materials, the life of diamond tools is 10 to 100 times that of cemented carbide tools, or even hundreds of times.

A very low coefficient of friction:
The friction coefficient between diamond and some non-ferrous metals is lower than other tools, the friction coefficient is low, the deformation during processing is small, and the cutting force can be reduced.

Very sharp cutting edge:
The cutting edge of the diamond tool can be very sharp, and the natural single-crystal diamond tool can be as high as 0.002 ~ 0.008μm, which can perform ultra-thin cutting and ultra-precision machining.

High thermal conductivity:
The thermal conductivity and thermal diffusivity of diamond are high, the cutting heat is easily dissipated, and the temperature of the cutting part of the tool is low.

A low thermal expansion coefficient:
The thermal expansion coefficient of diamond is several times smaller than that of cemented carbide, and the change in tool size caused by cutting heat is very small, which is especially important for precision and ultra-precision machining that require high dimensional accuracy.

Application of Diamond Tools
Diamond tools are mostly used for fine cutting and boring of non-ferrous and non-metallic materials at high speed. It is suitable for processing various wear-resistant non-metals, such as glass fiber reinforced plastic powder metallurgy blanks, ceramic materials, etc.; various wear-resistant non-ferrous metals, such as various silicon aluminum alloys; and various non-ferrous metals finishing.

The disadvantage of diamond tools is that their thermal stability is poor. When the cutting temperature exceeds 700 ° C ~ 800 ° C, it will completely lose its hardness; in addition, it is not suitable for cutting ferrous metals, because diamond (carbon) easily interacts with iron atoms at high temperatures. The carbon atoms are converted into a graphite structure, and the tool is easily damaged.

High-Speed Steel Cutting Tools
High-Speed Steel (HSS for short) is a high alloy tool steel with more alloying elements such as W, Mo, Cr, and V added. High-speed steel tools have excellent comprehensive performance in terms of strength, toughness, and manufacturability. In complex tools, especially for hole-making tools, milling cutters, threading tools, broaches, gear cutting tools, and other complex cutting tools, high-speed steel still plays an important role. High-speed steel tools make it easy to sharpen cutting edges.

According to different uses, high-speed steel can be divided into general-purpose high-speed steel and high-efficiency high-speed steel.

Universal High-Speed Steel Tool
General-purpose high-speed steel. Generally, it can be divided into two types: tungsten steel and tungsten-molybdenum steel. This type of high-speed steel contains 0.7% to 0.9% (C). According to the content of tungsten in steel, it can be divided into tungsten steel with a W content of 12% or 18%, tungsten-molybdenum steel with a W content of 6% or 8%, and molybdenum steel with a W content of 2% or without W. General-purpose high-speed steel has certain hardness (63-66HRC) and wear resistance, high strength and toughness, good plasticity, and processability, so it is widely used in the manufacture of various complex tools.

Tungsten steel:
The typical grade of general-purpose high-speed steel tungsten steel is W18Cr4V, (W18 for short), which has good comprehensive performance. The high-temperature hardness at 6000C is 48.5HRC, which can be used to manufacture various complex tools. It has the advantages of good grind ability and low decarburization sensitivity, but due to the high carbide content, the distribution is less uniform, the particles are large, and the strength and toughness are not high.

Tungsten molybdenum steel:
It refers to high-speed steel obtained by replacing part of tungsten in tungsten steel with molybdenum. The typical grade of tungsten-molybdenum steel is W6Mo5Cr4V2 (referred to as M2). The carbide particles of M2 are fine and uniform, and the strength, toughness, and high-temperature plasticity are better than those of W18Cr4V. Another tungsten-molybdenum steel is W9Mo3Cr4V (W9 for short), its thermal stability is slightly higher than that of M2 steel, its bending strength and toughness are better than W6M05Cr4V2, and it has good machinability.

High-Efficiency High-Speed Steel Tool
High-efficiency high-speed steel refers to a new type of steel that adds some carbon content, vanadium content and new alloying elements such as Co and Al to the composition of general-purpose high-speed steel, thereby improving its heat resistance and wear resistance. There are mainly the following categories:

High carbon high speed steel:
High-carbon high-speed steel (such as 95W18Cr4V), with high hardness at room temperature and high temperature, suitable for manufacturing and processing ordinary steel and cast iron, drills, reamers, taps, and milling cutters with high wear resistance requirements, or tools for processing harder materials, should not withstand large shocks.

High vanadium high speed steel:
Typical grades, such as W12Cr4V4Mo, (EV4 for short), with V content increased to 3% to 5%, good wear resistance, suitable for cutting materials with great tool wear, such as fibers, hard rubber, plastics, etc. It can also be used to process stainless steel, high-strength steel high-temperature alloys, and other materials.

Cobalt high speed steel:
It is a cobalt-containing super-hard high-speed steel. Typical grades, such as W2Mo9Cr4VCo8 (M42 for short), have high hardness, and its hardness can reach 69-70HRC. It is suitable for processing high-strength heat-resistant steels, high-temperature alloys, titanium alloys, etc. Material, M42 has good grindability and is suitable for making sophisticated and complex tools, but it is not suitable for working under impact cutting conditions.

Aluminum high speed steel:
It is a super-hard high-speed steel containing aluminum. Typical grades, such as W6Mo5Cr4V2Al, (501 for short), the high temperature hardness at 6000C also reaches 54HRC, and the cutting efficiency is equivalent to M42. It is suitable for manufacturing milling cutters, drills, reamers, gear cutters, broaches etc., for processing alloy steel, stainless steel, high-strength steel and superalloy and other materials.

Nitrogen superhard high speed steel:
Typical grades, such as W12M03Cr4V3N, referred to as (V3N), are nitrogen-containing super-hard high-speed steels, with hardness, strength, and toughness equivalent to M42. They can be used as substitutes for cobalt-containing high-speed steels for low-speed cutting of difficult-to-machine materials and low-speed high-precision machining.

The material of the cutting tool varies according to the type of tool, the material of the workpiece, the capability and mechanical properties of the machine tool, and the cutting form. It is very important to understand the difference and how to choose a material suitable for your tools!

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