HARD ALLOY APPLICATIONS (LITERATURE REVIEW)

ABSTRACT

Carbide alloys are unique materials that combine the outstanding mechanical properties of metals with excellent wear and corrosion resistance. Their wide range of characteristics makes them indispensable in many branches of industry and science. This article discusses the main areas of application for hard alloys. Their main ones are: the metal-cutting industry, the mining industry, the oil and gas industry, the aviation and space industries, medicine, electronics, and the automotive industry.

Carbide alloys continue to find new applications due to their unique properties and the constant development of technologies and methods for their production.

АННОТАЦИЯ

Твердые сплавы являются уникальными материалами, сочетающими в себе выдающиеся механические свойства металлов с превосходной стойкостью к износу и коррозии. Их широкий спектр характеристик делает их незаменимыми во многих отраслях промышленности и науки. В данной статье рассматриваются основные области применения твердых сплавов. Их основные следующие: металлорежущая промышленность, горнодобывающая промышленность, нефтегазовая промышленность, авиационная и космическая промышленность, медицина, электроника, автомобильная промышленность.

Твердые сплавы продолжают находить все новые области применения благодаря своим уникальным свойствам и постоянному развитию технологий и методов их производства.

Keywords: composition and structure of alloys; heat-resistant alloys; rotational; shock-rotary; shock-rotational; rotational-impact; cone.

Ключевые слова: состав и структура сплавов, жаропрочных сплавов, вращательный, ударно-поворотный, ударно-вращательный, вращательно-ударный, шарошечный.

Processing of metals by cutting

Cutting is a complex process in which the tool is subjected to various mechanical loads and abrasion by the material being processed, sometimes at elevated temperatures. Therefore, the performance of the tool, on the one hand, is determined by its strength and, on the other hand, wear resistance [1,2]. The failure of the cutter is possible for three main reasons: breakage due to macro-destruction of the blade; its gradual microwear under the influence of friction, leading to the loss of its original size and shape; and crushing of the cutting edge as a result of plastic deformation under the influence of cutting forces and high temperature (for alloys with reduced heat resistance).

Types of cutter wear. The wear of the cutter surface depends on the nature of the chips formed. When machining steels, as a rule, a continuous “drain” chip is formed, and the cutter mainly wears out along the front surface, on which a hole is formed under the influence of a continuously running chip: the rear surface also wears out at the same time, but less. Over time, the hole increases in depth and width, and its border approaches the cutting blade, and when it closes with a wear strip, the cutter fails [3].

Wear has a different character during the processing of brittle materials, which give a short, in the form of individual elements, "chip chipping". The hole is almost not formed because there is no prolonged contact of the chips with the front surface of the cutter. The performance of the cutter depends on the degree of wear on its back surface. It should be noted that in this case, the cutter blade experiences heavy loads because the removal of chips in the form of individual elements leads to a kind of variable load (greater strength is required from the alloy). The blade seems to re-cut. In addition, loads are concentrated on a narrow contact area along the cutting blade. The working capacity is significantly affected by the temperature developing in the cutting zone (on the contact surface, the order of temperatures is 1100–1500 °C at a distance of 0.2–0.3 mm at 700 °C, due to the thermal conductivity of the hard alloy).

Machining of steel and cast iron. A comparison of the resistance of VK and TK alloys in the processing of steel products shows that at very low cutting speeds, wear prevails as a result of mechanical effects on the cutting blade, which leads to chipping. Therefore, the advantage remains with the stronger WC-Co alloy. At these speeds, the TiC-WC grains are broken and pulled out, which causes intense wear. With some increase in speed, WC-Co still outperforms TiC-WC-Co, since, under these conditions, a build-up is formed on the edge, mainly in TiC-WC-Co due to their lower thermal conductivity. The build-up is periodically removed; there is a separation with the "particles" of the cutter, and due to this, increased wear [4].

With a further increase in speed, a hole forms in WC-Co alloys, and the resistance drops sharply. And for TiC-WC-Co, the resistance increases because build-up formation is reduced and vibration is reduced. WC-TiC-Co tends to crater less than WC-Co, hence the higher resistance. Higher speeds increase crater wear and flank wear. The maximum is explained by the fact that as the speed increases, the contact time of the chips with the cutter decreases, reducing wear, but the temperature rises, increasing wear. At the point of maximum, the effect of both factors is equalized, and then the increase in temperature prevails [5].

For cast iron, other patterns apply. Due to the lower pressure of the chips on the front surface of the cutter, the hole is formed to a much lesser extent, and the failure of the cutter is mainly determined by the amount of wear along the back surface. The superiority of WC-Co alloys is observed in almost the entire speed range due to their greater strength compared to WC-TiC-Co. The cutter blade experiences heavy loads with short chips. The advantage at high speeds is of no practical importance since durability is very low.

Machining of non-ferrous metals, titanium, stainless alloys, wood, etc. The composition and structure of alloys significantly affect the performance properties of the tool. The behavior of grades when cutting different materials, taking into account the properties of hard alloys, allows you to choose the right grades for various operating conditions when cutting [6].

When cutting non-ferrous metals and alloys (copper, aluminum, and bronze), WC-Co alloys should be used, which have an advantage over WC-TiC-Co alloys in terms of strength. Despite the formation of a "drain" chip, its pressure on the front surface of the cutter is very small, and there is no diffusion (non-ferrous metals do not interact with carbides). The low hardness of non-ferrous metals does not lead to high cutting temperatures. All this leaves an advantage for WC-Co alloys.

When machining titanium and its alloys, high temperatures develop in the cutting zone (due to the properties of titanium), so high cutting speeds cannot be used. At the same cutting speed, when processing titanium alloy VT2, a temperature of 1000–1100 °C develops, and steel, 500–550 °C. A comparison of the resistance of alloys in WC-Co and WC-TiC-Co shows that a significant advantage remains with the former. This is explained by the fact that, on the one hand, there are no differences in the solubility of the alloys. On the other hand, the lower strength of WC-TiC-Co alloys makes it easier to tear off the cutter particles together with welded-on particles of the material being processed, as well as chip the blade during possible vibrations due to low cutting speeds. The best results in cutting titanium alloys were obtained using cutters made of VK6-M and VK6-OM alloys (fine-grained) [1].

Nickel-based heat-resistant alloys are treated with WC-Co (BK8) alloys, which have an advantage over TK and TTK alloys due to their insufficient strength and lower thermal conductivity. The high viscosity of these alloys at low cutting speeds causes the occurrence of high temperatures and rapid wear of cutters, including carbide cutters.

The results of comparative tests of WC-Co and WC-TIC-Co alloys in the processing of stainless steels show the advantage of WC-Co alloys, although at low feeds and high cutting speeds (above 120 m/min), some alloys of the TK and TTK groups (high contents of titanium and tantalum carbides) have greater wear resistance, but their life periods are very short. The advantage remains with fine-grained WC-Co alloys.

The use of hard alloys for woodworking has a great effect because, despite its softness, wood has a strong abrasive effect on the tool. The requirements for a hard alloy are determined by the need to have not only wear resistance but a sufficiently strong cutting part of the tool that can withstand chipping. Alloys VK11-V and VK15 meet these requirements. Abroad, an alloy with 11% Co is widely used [4].

Destruction (drilling) of rocks.

During the exploration and extraction of minerals, the construction of tunnels and hydraulic structures, and engineering surveys, the destruction of rocks is carried out mainly with carbide tools. In this case, two areas of application of hard-alloy tools should be distinguished: drilling holes and wells; destruction of rocks by mining; and cutting tools using combines, cutters, and plows.

The loading scheme of hard-alloy rock-cutting elements depends on the drilling method. The most common at the present stage of technology development are the following methods: rotational, shock-swivel, shock-rotational, rotational shock, and cone.

In rotary percussion drilling, chisel, three-blade, and cross bits are used, equipped with prismatic and cylindrical hard-alloy products with a maple rock cutting blade; pin bits equipped with cylindrical hard-alloy products with a hemispherical or conical rock cutting head; as well as solid drills (monoblocks) with a chisel or three-blade rock cutting head.

The destruction of the rock occurs due to its compaction (the formation of a core under the blade) from impact loads, followed by the formation of cracks that extend to the surface of the face and the chipping of cantilever plates.

Rotary percussion drilling differs from percussion rotary drilling in that the rotation of the tool is carried out constantly by an electric, pneumatic, or hydraulic motor. With this method of drilling, more powerful equipment is used: pneumatic or hydraulic perforators.

In the shock-rotational method, two varieties should be distinguished: with remote perforators and submerged pneumatic or hydraulic hammers.

The rotational-impact method differs from the impact-rotational mode of force loading. Its shock loads are several times lower, but the axial force and torque are 2-3 times greater.

As a rock cutting tool, crowns equipped with prismatic and cylindrical carbide products with an asymmetric blade are used.

In roller drilling, roller bits are used as a rock-cutting tool. The drilling rig, creating pressure on the cone bit along its axis, rotates the rod and the cone bit at the same time. The cutters rest on the bottom of the well and, together with the bit, rotate around its axis. At the same time, under high axial pressure, the teeth located on the conical surface of the cutters penetrate into the rock of the bottom hole and destroy it.

Cone cutters are equipped with cylindrical teeth, mainly with a wedge or hemispherical head.

For mining combines and cutters, radial, radial-face, tangential, and rotating cutters are used, and cutters and knives are used for plows.

To equip drilling and mining tools, hard alloys of the VK group are used. Table 1 shows the composition and physical and mechanical properties of hard alloys for mining tools [5-6].

Table 1.

Alloys for mining tools

Alloys similar in composition are used by a Swedish company (Table 2).

Table 2.

Sandvik Coromant drilling carbide properties

The most effective grades for equipping mining tools are alloys of the VK-KS group, which are produced according to technical specifications [4].

Table 3.

Composition and properties of alloys of the KS group

Analysis of the data given in tables 1 and 3 shows that the strength of WC-Co alloys of the KS group is on average 31–47% higher than that of conventional WC-Co alloys; by 32–42% higher than that of WC-Co alloys of group B; and by 31–33% higher than that of WC-Co alloys of the VK group. The service life of drilling tools equipped with alloys of the VK-KS group is 30–50% higher than that of tools equipped with grades of other groups.

Conclusion

In conclusion, hard alloys are extensively used in drilling applications due to their exceptional properties and performance advantages. These alloys, commonly known as cemented carbides or tungsten carbides, are composed of a combination of tungsten carbide particles and a metallic binder (often cobalt). The use of hard alloys in drilling offers several benefits:

• High Hardness: Hard alloys have an extremely high hardness, making them ideal for cutting and drilling through tough materials such as rocks, metals, and composites.

• Wear Resistance: Their hardness also grants them excellent wear resistance, ensuring prolonged tool life even under demanding drilling conditions.
• Heat Resistance: Hard alloys exhibit good thermal stability, enabling them to withstand the high temperatures generated during drilling operations.
• Strength and Toughness: They possess high strength and toughness, reducing the risk of chipping or fracturing during drilling, which contributes to better tool reliability.
• Versatility: Hard alloys can be formulated with various compositions, allowing manufacturers to tailor them to specific drilling tasks and materials.
• Cost-Effectiveness: While hard alloys can be more expensive than traditional tool materials, their extended tool life and improved drilling efficiency often justify the investment.
• Wide Range of Applications: Hard alloys find application in a diverse range of drilling operations, including oil and gas exploration, mining, construction, metalworking, and manufacturing industries.
• Cutting Speed and Efficiency: They enable higher cutting speeds and improved drilling efficiency, reducing overall drilling time and enhancing productivity.

In summary, hard alloys are a crucial component in modern drilling operations, offering the necessary durability, efficiency, and cost-effectiveness to meet the challenges of drilling through tough materials in various industries. Their widespread use has significantly advanced the field of drilling technology and continues to play a vital role in facilitating various industrial processes.

References:

1. Parmonov S.T. Increasing the abrasion resistance of hard alloys used in the mining and metallurgical industry by adding ultradisperse modifiers // Journal of Pharmaceutical Negative Results – 2022. Vol. 13. № 9. – P 7474-7479
2. Parmanov S.T., Shakirov Sh.M., Sharipov K.A., Sadaddinova S.S. Percussion abrasive wear of drobiles on working details made from solid alloys // UNIVERSUM: ТЕХНИЧЕСКИЕ НАУКИ – 2022. № 5 (98). – P 51-55
3. Panov V.S., Chuvilin A.M. Technology i svoystva spechennyx tverdyx splavov i izdeliy iz ix [Technologies and properties of sintered hard alloys and products from them] // – Moscow. COPPER. 2001. – P 103-107 [in Russian]
4. Parmanov S.T., Shakirov Sh.M., Sharipov K.A., Khujakulov N.B. Scientific basis of temperature and time dependence in the process of heating and tungsten carbide-based solid alloy powders // Web of Scientist: International Scientific Research Journal – 2021. Vol. 2. № 12. – P 604-609
5. Nurmurodov S.D., Rasulov A.Kh., Allanazarov A.A., Pardaev T.U.  Influence of  structural-textural  features of turbo-alloy products using tungsten treatment on their strength properties // Technical science and innovation – 2020. №12. – P 103-104
6. Parmonov S.T. Tungsten-containing hard alloys and their role in the production enterprises of our country // Composite materials – 2021. №3. – P 202-204