Coatings of hard alloys for cutting tools

the processing of metals has shown that one effective way of increasing performance is the use of new tool materials.

coated Tool


the Coating of the cutting tool must increase:

hardness, in order for a long time to save cutting properties of the tool;

— ability to maintain necessary hardness when cutting Mella;

— tool.

Cover can be the tool of any geometrical complexity

currently, approximately 75% of the world’s cutting tool made of hard alloy.

Qualitatively new stage of production of cutting tools associated with the opening at the end of the last century, technologies of ion-plasma wear-resistant coatings. In the world of technology for hardening is represented by two methods: chemical vapor deposition method (Chemical Vapour Deposition — CVD) method and physical vapor deposition coatings (Physical Vapour Deposition — PVD). In Russia, the widespread industrial application has received PVD-methods of applying protective coatings on cutting tools. This is because CVD technology involve the use of expensive high-purity chemical reagents (TiCl4, NH3, etc.) and precise control of the products of chemical reactions in the chamber. And the application of PVD coatings using arc or glow discharge (magnetron) has a better performance and not so sensitive to slight deviations of technological parameters.

The Variety of currently used methods of physical vapour deposition of wear-resistant coatings is reduced to evaporation or ion sputtering of titanium or its alloys, the ionization and heterogeneous reaction on the surface of the tool atoms and metal ions and the reaction gas, leading to the formation of a nitride, carbide, carbonitride.

coated Tool can be found in any industry

Structure and the adhesion of the coating tool and their cutting properties defines many parameters: increasing the degree of ionization, velocity, and flux density of the sprayed particles, optimization of the temperature of the coating, the use of ionic cleaning of the substrate, the accelerating voltage, Rvarious industry modes of application, the configuration tooling, conducting advanced tive ion etching or doping, and many others features determine the structure of the coatings and formationtion of the interface «coating — substrate».

In the early 80s of the last century started to be applied and immediately showed the economic efficiency of TiN coating. The next step was the creation of two-layer coatings consisting of successively deposited layers of titanium carbide TiC or titanium carbonitride TiCN and a thin surface layer of aluminum oxide Al2O3.

The Alternative served as a multi-coating type TiCTiCNTiN. It should be noted that the concept of «layered» in many cases, very arbitrary, since the methods of spraying can achieve the absence of distinct phase boundaries between the layers and between the coating and the substrate. Multilayer hard wear resistant coatings have a high crack resistance, improved adhesion, high impact strength, a lower level of internal stresses and strains on the boundary «coating — substrate» due to the alignment of coefficients of thermal expansion. For example, the TiCN coating has a layered two-phase structure of TiN–TiCN that increases the strength and viscosity characteristics compared to TiN coating.

Coated cutting tool point method

In the last decade developed and widely usedare different combinations of coatings with the use of a thin external hard lubricant coatings (such as TiAlN/MoS2) provide good chip removal. Low coefficient of friction and high wear resistance.ut very hard diamond-like coatings (diamondlikecarbon coatings — DLC). However, they have a serious wealth: very high level of internal stress, leading to embrittlement and flaking at high constroke stress which limits the thickness ofwell, coatings up to 1 ám. Another problem of such coatings — low thermal conductivity, which can lead to them local graphitization with subsequent leaching. Toptions operating temperature limit is restricted to 250 °C, and treit is necessary to use lubricating coolants (GM). Coating cubic boron nitride (CBN) aboutladyt high level of internal stresses and the thickness of the coating is not more than 0.1 microns.

In the face of competition companies are forced to constantly improve their processes in the area of reducing the complexity, improving the quality and efficiency of the equipment.

During the cutting process, the maximum efficiency is achieved when the integrated use of high-tech equipment, equipped with CNC machining and modern metal cutting tool, providing greater cutting speed and performance.

Most versatile group of cutting materials, allowing the to complete the processing of the vast majority of metal non-metallic materials. Carbide tools are designed for cutting speeds up to 300 m/min (drill 50-70 m/min, cutting-edge developments to 90-180 m/min); used, in bulk, on machine manufacturers with spindle speed average up to 10,000 rpm To improve the properties (increase of hardness, decrease of the radius of curvature of the cutting edge and, consequently, to increase the resistance of the tool) manufacturers are committed to reducing the grain of alloys.

Manufacturers offer a wide range of designs, geometries processing of all metallic materials. From foreign suppliers in Russia work: Sandvik Coromant, Iskar, Wolf, Seco, Mitsubishi, Walter, Korloy, Kennametal, Dormer.

Among Russian producers note of LLC «SKIF – M» (Belgorod) — developer and manufacturer of milling cutters with interchangeable cutting plates of hard alloy and JSC «Serpukhov tool plant «Twintos». Plant «Twintos» also undertook the original development of designs of cutters, software, and manufactures milling method visitvirginia of carbide blanks manufacturers.

Setting spray

One of the drawbacks of almost all the vendors listed above is the lack of services for regrinding solid carbide milling cutters and carbide recycling plates and working parts of the cutters. It should also be noted that all of these providers focused primarily on the sale of the tool for the new, modern equipment, and the selection of carbide tools with SMP for the equipment of domestic production being extremely reluctant.

For dry processing of well-established TiAlN coating. This coating allows to improve adhesion, increase impact strength, reduce the coefficient of friction, have high tremendoustomato.

At the same time, the coating increases the radius of curvature of the cutting edges that have adverse impacts, for example, when removing a small allowance.

Comparative table of coating a cutting tool

Some coatings are characterized by high internal stresses leading to delamination of the coatings. The most applicable coating on the profile tools and inserts, as when regrinding coating on parts subjected to grinding, completely destroyed.

In Russia, the coating is OOO «Technological coverage» (Moscow), NPF «Elan Practitioner»(Nizhny Novgorod).

the Main types of PVD coatings (characterized by a thickness of 1-3. 5 µm, therefore, applied to cutting edges with a small radius to reduce cutting forces, improve breaking, prevent vibration) and CVD coatings with a thickness up to 20 µm (Al2O3). The main difference between these coatings is the method of application: PVD coating (400–500oC) used physical vapour deposition, CVD (1000–1100оС) chemical.

Shock mechanical destruction of the tool also adversely affects the coatings, and therefore their effectiveness may be reduced when using imperfect equipment.

In addition to wear-resistant coatings (the most common nitride TiAlN, TiAlCrN, TiN) have been used hard lubricant coating having a very low coefficient of friction and reducing the cutting forces and the chip evacuation (TiO2, WO3V2O5).

Tool with brazed carbide inserts or replaceable carbide knives for end mills, the most spoken in Russia. Its advantages: simplicity, low cost. The main drawback is its low performance, the need for high-quality sharpening. The cutting speed rarely exceeds 100 m/min

the Tool with coating and without it

Solid CVD-coated grade

the Reliable contact of the coating with high strength.
the Obstacle is the formation of build-up and high wear resistance.
the Optimal choice for roughing of stainless steels
High performance in low carbon and structural steels.
High durability when machining hard materials.

Hard alloys without coating

Hard alloy tool materials are obtained by powder metallurgy which are based on tungsten carbide, titanium, tantalum with the use of cobalt binder (TaC, TiC and WC). Vacuum sintering improves physical characteristics (strength, wear resistance, heat resistance, etc.) of the materials and extends their field of application.
the benefits of a Wide range of manufactured brands of alloy for the groups R,M,K the Resistance to the formation of thermoresin.VOZMOZhNOSTI manufacturing SMEs with a high degree of accuracy of the geometric dimensions.

Hard alloys coated РVD

High efficiency machining of cast irons, carbon, stainless and heat resisting steels.
fine-Grained structure has high hardness and toughness, which prevents spalling and enhances durability of the cutting edge.
Advanced technology РVD coating provides high hardness and prevents oxidative deterioration at high temperatures.

Solid alloy coated РVD

the

Ultra-fine grained cemented carbide

Ultra-fine grain hard alloy has higher mechanical strength in comparison with hard alloy having an average grain size. This allows significantly increase cutting speed.

Ultra-fine grained cemented carbide

the

Hard alloys diamond-coated

Increases tool life by 150%.
Reduced coefficient of friction between the chip and the front surface of the SMP coating (~ 10 microns) reduces the heating plates.
Reduced built-up edge
improves the quality of the treated surface.

Solid alloy plated with diamond

the

Hard alloys with DLC coating

Low friction coefficient on the front surface (<0,1) provides high-quality processing.
ensuring a high resistance when machining non-ferrous metals can be Applied to process aluminum, plastic, wood Coating used for turning SMP, drills and end mills.

Hard alloys with DLC coating

the

Polycrystalline diamond (PCD)

Plastiny of PKA (polycrystalline artificial diamond) sintered at high temperature on the basis of the medium and small diamond crystals and have a high hardness and wear resistance.
materials:
Aluminum and copper alloys
Aluminum alloy with high silicon content
plastic materials

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