RU2584275C1 - Method for prediction of wear resistance of hard alloy cutting tools - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metal forming and can be used for forecasting and control over carbide tool durability in production, application or certification. Testing is performed on change of initial parameter from properties of structure made during carbide tool manufacture. Reference wear resistance tests during cutting of materials that exhibit intense adhesion wear at optimal or close to optimal cutting speed, constructing reference-correlation relationship “initial parameter - wear resistance”. Statistical control is performed only input parameter value for current batch of carbide cutting tools, forecast of wear resistance for current batch of carbide cutting tools based on dependence. Initial parameter is value of concentration of hydrogen contained in oxide mass produced during oxidation of hard alloy cutting tools, reducing wear resistance of hard alloy cutting tools of applicability group K increases.

EFFECT: technical result is improved accuracy and reduced labour input when predicting wear resistance of hard alloy cutting tools.

3 cl, 1 dwg

Description

The invention relates to the field of metal cutting and can be used to predict - control the wear resistance of carbide cutting tools in their manufacture, use or certification.

A known method for determining the wear resistance of hard alloys is that the test material is placed in an alternating magnetic field with an intensity of about 5 Oersted, the magnetic permeability of the material is measured, and the magnitude of the material’s wear resistance is determined from the magnetic permeability - resistance graph plotted for the reference sample [ SU A.S. 268720, IPC G01N 3/58, BI 1970, No. 14].

One of the disadvantages of this method is that the measurement does not take into account the influence of the mass and demagnetizing factor of products, which often have different shapes and dimensions on the value of magnetic permeability, which reduces the accuracy of the measurements. In addition, the operational characteristic - wear resistance is controlled by this method by assessing the physical condition using relative magnetic permeability in only one of the components of the hard alloy - cobalt bond. This is because tungsten carbide is a paramagnet and its contribution from magnetization to the total relative magnetic permeability is small. Therefore, using this method, essentially, the relative magnetic permeability of cobalt, its quantity and deformation state are evaluated. Moreover, other properties of the surface and volume of the hard alloy are not taken into account at all, including the cohesive and adhesive state at the phase boundaries and in the volume of the components of the hard alloy, etc. Due to the reasons considered, this method is characterized by low accuracy in assessing the wear resistance of hard alloys.

A known method of controlling the cutting properties of a batch of carbide tools, according to which first they act on each tool (carbide plate) from the batch, a control parameter is recorded, then several tools from the batch are selectively subjected to mechanical wear and the cutting properties of the tools of the entire batch are determined. The impact on each tool is carried out by uniformly distributed pulsed heating, a chronological thermogram is recorded, the thermal diffusivity of each instrument is determined as a control parameter, according to the results of a selective wear mechanism depending on the thermal diffusivity, and the cutting properties of the instruments of the entire batch are determined using the obtained dependence [SU A .FROM. 1651155, IPC G01N 3/58, BI 1991 No. 19]. The selected initial parameter in this method is the thermal diffusivity. The main disadvantage of this method is that it is very difficult, more or less accurately, to determine the rate of heat propagation in materials in which free electrons are the heat carriers. Hard alloys are such materials, and their heat transfer is ensured by the movement of electrons. The thermal diffusivity of all hard alloys differs by an insignificant amount. Therefore, it is very difficult to determine the fluctuations (changing the wear resistance) of the thermal diffusivity for one particular grade of hard alloy (they are almost invisible). The latter is fraught with great technical difficulties. The proper provision in this situation of control operations with precise - acting, recording and auxiliary instruments and devices guaranteeing the necessary accuracy will entail a significant increase in the cost of control operations. As a result of this, this control method is not very promising for use in both laboratory and production conditions.

A known method for predicting the wear resistance of a cutting tool, selected as a prototype and consisting in the following. Carry out benchmark tests of cutting tools at an optimal or close cutting speed, conduct tests to change the value of the initial parameter on the properties of the surface polyoxide structure of the hard alloy formed during its heating, build the reference correlation "initial parameter - wear resistance", perform statistical monitoring only initial parameter values for the current batch of carbide cutting tools. After that, wear resistance is predicted for the current batch of tools based on the relationship:

where T (current), min - wear resistance in minutes - the average predicted time of trouble-free operation of carbide cutting tools undergoing tests from the current batch of samples;

T (reference), min - average wear resistance in minutes for carbide cutting tools from a reference batch of carbide products;

τ (reference), ps - the average value of the selected initial parameter obtained by measuring the characteristics of the surface polyoxide structure of carbide cutting tools from a reference batch of carbide products;

τ (current), ps - the average value of the selected initial parameter obtained by measuring the characteristics of the surface polyoxide structure of carbide cutting tools from the current - controlled batch. In this case, the value of the positron lifetime embedded in the surface and near-surface layers of hard alloys and estimating the electron density of their structure is used as the initial parameter. The magnitude of the electron density predict the wear resistance of manufactured cutting tools. [SU A.S. 2251095, IPC G01N 3/58, BI 2005 No. 12]. The main disadvantage of this method is the high organizational complexity in its implementation. To implement this method, a radioactive source is required. In accordance with the standards for its maintenance, there are high requirements. It is necessary to have a special room for its storage. The measurement of the relevant parameters and the processing of the results obtained can only be done by specially trained and trained personnel. Using this method, the structure is assessed at the atomic level and not always comparing these results with the results obtained by wear resistance leads to an accurate forecast. This method allows you to sort - to predict the wear resistance of hard alloys similar in appearance and degree of defective structure. A comparison of structures that differ greatly in appearance and degree of defectiveness gives quite noticeable errors in predicting the wear resistance of carbide cutting tools. As a result of this, this method for predicting wear resistance does not exactly characterize the operational properties determined by the degree of defective structure, which ultimately reduces the degree of tightness of the correlation between the initial parameter and the wear resistance of cutting tools. Nevertheless, this control method informatively reflects the operational state of the surface structure of the tool material, which is important for establishing a relationship between this characteristic and adhesive wear, which largely depends on the type and degree of imperfection of the surface layer, and we choose it as a prototype.

The objective of the proposed method for predicting the wear resistance of carbide tungsten - cobalt (group K) cutting tools is to increase accuracy and reduce the complexity in predicting the wear resistance of carbide cutting tools. Prediction is based on a close correlation between the wear resistance and the concentration of hydrogen contained in the oxide structure of the hard alloy formed during the oxidation of carbide cutting tools in an electric furnace with open access to atmospheric air at a heating temperature corresponding to the optimum cutting temperature with this tool material. With a decrease in the hydrogen concentration in the oxide structure of hard alloys of the applicability group K, the wear resistance of cutting tools made from these hard alloys increases when cutting steels and alloys that cause intense adhesive wear.

The task when predicting the wear resistance of carbide cutting tools of the applicability group K in the proposed method is solved by using the selected initial parameter and includes: conducting benchmark tests of cutting tools for wear resistance in the process of cutting materials that cause intense adhesive wear, at an optimum or close cutting speed, oxidation tested cutting tools at a temperature corresponding to the average of operating in the contact zones, check lioksidnyh samples on the change in the initial parameter, the construction of the reference - correlation "wear - original parameter" statistical control only parameter values starting from the carbide cutting tools, wear forecast for the current batch of carbide tools on the basis of the relationship:

where a _E and b _E are constant coefficients:

of them:

T _PT - the current wear resistance in minutes for carbide cutting tools that have been tested, from the projected current batch of carbide products;

ω _PT - the current value of the selected initial parameter obtained by monitoring the oxide mass formed on the surface of carbide cutting tools during their oxidation from the current controlled batch of carbide products;

и $$T_{{Э}_2}$$

- износостойкость в минутах для двух независимых выборок твердосплавных режущих инструментов из эталонной партии твердосплавной продукции; $$T_{E_{\mathrm{one}}}$$

and $$T_{E_2}$$

- wear resistance in minutes for two independent samples of carbide cutting tools from a reference batch of carbide products;

и $${\omega }_{{Э}_2}$$

- средние значения величин выбранного исходного параметра, полученные при контроле оксидной массы, сформированной на поверхности твердосплавных режущих инструментов при их окислении, для двух выборок образцов из эталонной партии продукции, отличающийся тем, что с целью повышения точности прогнозирования износостойкости в качестве исходного параметра используют величину концентрации водорода, содержащегося в оксидной массе, полученной при окислении твердосплавных режущих инструментов, с уменьшением которой износостойкость твердосплавных режущих инструментов группы применяемости К возрастает. $${\omega }_{E_{\mathrm{one}}}$$

and $${\omega }_{E_2}$$

- average values of the values of the selected initial parameter obtained by monitoring the oxide mass formed on the surface of carbide cutting tools during their oxidation for two samples of samples from the reference batch of products, characterized in that in order to increase the accuracy of predicting wear resistance, the concentration value is used as the initial parameter hydrogen contained in the oxide mass obtained by the oxidation of carbide cutting tools, with a decrease in which the hardness wear resistance longwall cutting tools Group applicability to the increases.

The method also differs in that carbide cutting inserts are used as carbide cutting tools.

The method also differs in that carbide cutting tools from a previous batch of purchased products are used as carbide cutting tools from a reference batch.

The internal structure of the carbide cutting tool of the applicability group K, which is formed in the process of manufacturing a hard alloy, has a great influence on its wear resistance. One of the most important characteristics of the internal structure that determines the most important physical, mechanical and operational properties of carbide cutting tools of this group is its ability to interact with oxygen. Oxygen can have a beneficial effect both on the formation of the structure of the hard alloy, and on the processes that then develop in the zones of interaction of the tool and the processed materials during the operation of the cutting tool. The accumulation of oxygen in the internal structure of hard alloys can occur at various stages of the manufacture of both the hard alloy itself and its individual components. On the surface of powder particles - the initial components of hard alloys: tungsten carbide and cobalt during their manufacture, thin oxide films are formed, which then, at the sintering stage, are a screen against the penetration of the indicated components of other elements and, in particular, hydrogen. At the same time, the main operations associated with the manufacture of directly hard alloys (for example, sintering) and its components occur in a hydrogen-containing medium and, accordingly, the effect of hydrogen on the formation of the composite structure as a whole is significant.

Hard alloys are sintered at sufficiently high temperatures. Hydrogen, on the one hand, through a system of different pores, penetrating into the deep regions of hard alloys of the applicability group K, dissolves and removes an impurity oxygen-containing medium in the form of water vapor, and on the other hand, participates in the formation of solid solutions, carbohydride, hydroxyhydrohydride, carbonitrohydride and other compounds. Removing the oxygen-containing medium with hydrogen from the composite and the formation of various hydrogen-containing compounds reduces the performance of carbide cutting tools of applicability group K when they process materials that cause intense adhesive wear. Surface and bulk oxyhydride and hydride thin films and solid alloy composition structures have high thermal conductivity and low dielectric constant. Because of this, they, unlike oxide compounds, do not provide sufficiently reliable shielding of intermolecular interaction in the contact zones of the tool and the processed material. In addition, the crystallographic structure of these compounds does not contain planes with a dense packing of atoms — planes of easy slip, as, for example, for oxides. The latter circumstance excludes the fulfillment of the function of solid lubricant by them at a low and optimal operating temperature of carbide group of applicability K of cutting tools. Operation of these cutting tools at higher temperatures leads to increased wear. In this regard, on the one hand, oxygen and an oxygen-containing medium during operation of carbide cutting tools diffuse into the contact zones and, together with the oxygen in the surrounding gas medium, participate in the formation of dissipative structures that protect the working faces from wear. On the other hand, free hydrogen and hydrogen in the form of various hydride compounds accumulated by the carbide structure reduces the activity of the oxidizing medium and prevents the formation of dissipative structures that protect contact surfaces from adhesive wear. From the presented it follows that the operational characteristics of carbide cutting tools of the applicability group K when they process materials that cause intense adhesive wear will increase with a decrease in the structure of the hard alloy of hydrogen or its compounds.

As a rule, hydrogen, in the deep layers of the carbide structure, is in a different aggregate form: in a free state, in a state of weak interaction with components of the structure, and in a state of strong interaction with components of the structure. A part of the hydrogen in a free state, during mechanical activation and heating of the carbide contact surfaces of cutting tools during their operation, can undergo ionization and interact with the components of the hard alloy and gas elements of the environment, and the other part, on the contrary, desorb to the surrounding atmosphere or diffuse , for example, in the structure of the processed material. Hydrogen, which was initially in the form of both weak and strong interaction with the components of the hard alloy during mechanical and thermal activation of the contact surfaces of the carbide cutting tool and the bulk structure as a whole, takes part, along with impurities and elements of the surrounding gas atmosphere, in the formation of various hydride, oxyhydride, oxycarbohydride, oxy nitrohydride and other bulk and surface compounds. These hydrogen-containing compounds, both in the internal structure of the hard alloy and in the zones of contact interaction, have a great influence on the performance of carbide cutting tools of applicability group K and, first of all, on their wear resistance. With an increase in the initial concentration of hydrogen in the structure of the hard alloy obtained during sintering, the concentration of hydrogen-containing compounds formed in the contact zone during the operation of carbide cutting tools increases.

The most favorable conditions for maintaining high operational performance of cutting tools during their long-term functioning exist with constant destruction and subsequent formation of oxide films and structures with a developed internal structure in the contact zones on the surfaces of the cutting wedge. Such oxide formations can occur at the highest oxidation state of the components of the structure of hard alloys and their impurities. In this case, oxide formations have low electrical conductivity, dielectric loss tangent, and thermal conductivity. They effectively screen intermolecular interaction and are a good solid lubricant. The wear resistance of carbide cutting tools of the applicability group K in the process of processing materials that cause intense adhesive wear, while achieving the highest performance. This is primarily due to the presence of high relative permittivities of the surface oxide formations and the presence in the crystallographic structure of these structures of a large number of planes, the relative shift of which occurs at sufficiently low contact stresses, which is important for creating a lubricating effect between sliding surfaces. The presence in the region between the front surface of the cutting wedge and the chips, as well as between its rear surface and the treated surface of the material of oxide structures, with the presence of hydrogen, significantly reduces their effectiveness both as a screen against intermolecular interaction of the contacting surfaces, and as a material that plays the role of solid lubricant. This occurs as a result of an increase in the emerging intercontact oxyhydride structure of electrical conductivity, the dielectric loss tangent, thermal conductivity and, as a result, a decrease in its relative dielectric constant, which determines the level of intermolecular interaction of the contacting surfaces during intensive adhesive interaction of the carbide cutting tool and the processed materials. When hydrogen is embedded in the crystal lattice of an intercontact oxide structure, first of all, its density and lightness in the relative slip of crystallographic planes decreases. As a result of this, the lubricating characteristics of this oxide-containing hydrogen-containing compound are reduced. Thus, the hydrogen contained in the structure of the hard alloy prevents the formation of effective dissipative oxide structures in the contact zones or significantly impairs their ability to shield the intermolecular interaction of the contacting surfaces and perform lubricating functions in the contact zones. As a result, the wear resistance of carbide cutting tools of the applicability group K when they process materials that cause intense adhesive wear is reduced.

The process of saturation of the structure of hard alloys with hydrogen during sintering is influenced by many factors.

The most dispersed fractions, components of the solid-phase composition, adsorb hydrogen to a greater extent and are more likely to form compounds with different strengths of bond.

Impurities have a large effect on the accumulation of hydrogen by the structure of the hard alloy. One part of the impurities that make up the components contributes to the adsorption of hydrogen and its accumulation in the structure. The other part prevents the accumulation of hydrogen in the composition of the components. A significant amount of adsorbed hydrogen is located in nanoscale pores, which are formed in the components of the carbide composition upon evaporation of low-melting elements. With an increase in the composition of the solid alloy of finely dispersed graphite in a free state, the storage properties of the carbide composition with respect to hydrogen also increase. In this case, a significant concentration of hydrogen is adsorbed and stored in the porous graphite system. Moreover, the pores of nanosized size are the most effective for adsorption and placement of hydrogen in the structure of all components of the hard alloy and the boundary region. Such a porous system is formed by the evaporation of low-melting both metallic and non-metallic elements and compounds. In this case, the electron density of the structure of the components of the hard alloy decreases, and its acceptor properties increase. The latter circumstance is a significant incentive for the adsorption by a porous surface of both tungsten carbide and cobalt of gas elements and, first of all, with an insignificant atomic weight, which is hydrogen. The driving force of the process of adsorption of hydrogen molecules by the inner surface of the pore is the electric field created at the stages of the formation of the porous system and, in particular, during the evaporation and sublimation of its own atoms and clusters, as well as during the evaporation and sublimation of impurity elements and compounds that make up the components of hard alloys .

The phenomenon of adsorption and desorption of gas elements, in particular hydrogen, directly affects the processes of formation of a porous system in the components of hard alloys. This occurs when the formation of a porous system during sintering is carried out due to the predominance of certain impurities in the composition of the components or the presence of a certain structural state in the system, accompanied by periodic evaporation and subsequent condensation. In this case, the formation of the porous system can occur both with the progressive nature of its development, and vice versa, when the development of the porous system during the sintering process damps. In the first case, the process of hydrogen accumulation in the components of the hard alloy will continuously increase, and in the second case it will continuously decrease.

The successful functioning of carbide cutting tools of the applicability group K in the processing of materials that cause intense adhesive wear should be accompanied by continuous formation and continuous subsequent destruction of thin oxide structures on the contact surfaces of the cutting wedge. Moreover, as a result of oxidation reactions of the main carbide component of the carbide composition, by-products are formed, including by-products: carbon monoxide and carbon dioxide. With limited access to the contact zone of the oxidizing medium, the concentration of carbon monoxide and carbon dioxide may be equal. In this situation, the addition of hydrogen from the deep layers of the hard alloy to the contact space due to diffusion can also lead to a shift in the thermodynamic equilibrium between the oxidation and restoration of the contact surfaces of the cutting wedge towards recovery processes. When the reduction processes dominate in the contact zones, the formation of oxide structures ceases. This will lead to the activation of adhesive phenomena in the contact zones and the development of microwelding processes between tool and processed materials.

With an increase in the amount of incoming hydrogen from the structure of the hard alloy to the contact zone, the strength of the resulting microwelding will continuously increase. On the one hand, in this case, microwelding processes, due to intermolecular interaction, will more and more be carried out in a protective hydrogen medium, which guarantees high quality of the compounds formed. On the other hand, the inevitable destruction of the formed microwelding joints due to cutting forces will be accompanied by more and more destructive consequences for the cutting wedge - its surfaces, surface layers and the volume as a whole. This will occur due to the fact that with an increase in the amount of hydrogen in the contact zones and an increase in the strength and quality of the directly welded seam, the formation of the joint will not be destroyed by the body of the material being processed, but by the body of the cutting tool. The latter is due to the fact that the tensile strength of hard alloys is significantly lower than the tensile strength of the class of processed materials, which cause intense adhesion wear during cutting, especially chromium-nickel steels and alloys.

The intensification of adhesive phenomena leads to an increase in contact stresses. There is a disproportionate increase in shear stresses compared to normal stresses. At the same time, the friction coefficients on both the front and rear surfaces of the cutting wedge increase. The temperature in the area of chip formation increases significantly. The latter circumstance, in turn, leads to an intensification of adhesive phenomena, the magnitude of the degree of plastic deformation of the sheared layer — shrinkage of the chips — sharply increases. As a result, microfractures of the contact surfaces progressively increase, the overall wear intensifies significantly and can result in macrocracking of the cutting wedge.

Not all hydrogen that has penetrated the structure of hard alloys as a result of sorption processes has a negative effect on the properties of its components and interfacial boundaries. Hydrogen, which during the operation of carbide cutting tools does not interact with the components of the hard alloy and the oxygen entering the contact zone, but due to desorption, escapes into the surrounding gas atmosphere, does not have a destructive effect on performance. Only the active part of the hydrogen adsorbed by the structure that interacts with the components of the hard alloy with the formation of chemical bonds of various strengths has a negative effect on the structure of the hard alloy and on contact processes. Such hydrogen-containing compounds, being in contact zones, participate in redox reactions and prevent the formation of oxide film structures and other oxide formations. This circumstance significantly reduces the quality of dissipative processes in the contact zones and leads to a decrease in the wear resistance of the carbide cutting tool of the applicability group K in the processing of materials that cause intense adhesive wear.

A great influence on the wear resistance of cutting tools is exerted by the processes of formation, sublimation and subsequent condensation of oxides belonging to the components of the hard alloy and the material being processed. As a result of the condensation of a gaseous oxide substance occurring in the intercontact space, on the contact surfaces of both the processed and the tool materials, thin oxide films of nanosized size are formed, which shield the intermolecular interaction of the rubbing objects, and, if they are sufficiently layered, break down and play the role of a solid lubricant.

Hydrogen accumulated by the structure of the hard alloy penetrates into the contact zones of the tool and the processed material and interacts with their elements. The resulting hydrides, oxyhydrides, and oxides with impurity hydrogen exert a great influence both on contact processes and on all the main operational characteristics of carbide cutting tools.

When hydrogen interacts with oxides formed in the contact zone, a rather high concentration of complex compounds is formed, which, in particular, also have hydrogen bonds. Hydrogen, as a rule, takes an active part in the reduction processes and prevents the formation of higher oxides. The formed oxide and oxyhydride compounds in the presence of hydrogen in their composition strongly change their thermodynamic and kinetic properties. So, when entering the intercontact space, from the structure of a solid alloy of hydrogen, the concentration of higher tungsten and cobalt oxides formed in it decreases and the concentration of lower oxides increases. A feature of this phenomenon is that the lower oxides undergo sublimation at higher temperatures, acting in the contact zones of the tool and the processed materials, or their transition from solid to gaseous state is completely excluded. It may turn out that the temperature range of the transition to the gaseous state, followed by condensation and the formation of effective oxide film systems on the contact surfaces, due to the presence of hydrogen, will be significantly higher than the optimum operating temperature of this carbide. In this case, the cutting wedge of carbide cutting tools, when used in cutting modes that cause low temperature in the contact zones, will not have thin oxide films on the contact surfaces of the effective screen, which protects them from intermolecular interaction reactions. In addition, due to the absence of normal phenomena of oxidation, sublimation, condensation and the formation of thin oxide layers and layers, the contact surfaces of the carbide cutting tool of the applicability group K will not be subjected to effective lubricating actions. At high operating temperatures of carbide cutting tools, above optimal temperatures, an accelerated process of destruction of the carbide structure in the contact zones due to intense oxidative, diffusion and abrasive wear will occur. In both cases, the wear resistance of cutting tools will be intensively reduced.

During adsorption, hydrogen is placed in various objects of the structure of hard alloys. The most effective place for hydrogen to be placed is in pores, cracks, and various types of vacancy defect systems of structure components and their compounds.

Being located due to adsorption of carbide grain in the porous system, hydrogen weakens the bonds between tungsten and carbon. In addition, its extensive presence makes the structure of carbide grain substantially heterogeneous in physicomechanical and chemical properties, which, in fact, violates the integrity of the grain structure under the action of alternating loads in the form of compression and tension that arise at the stages of formation of the adhesive joint and its destruction.

In the cobalt matrix, hydrogen is also located in cracks and pores arising at the stages of grinding cobalt powder. When heated, the hydrogen medium creates high pressures in the cracks having a nanoscale size and favorable conditions for the formation of these particles of increased fragility in the material.

During sintering of hard alloys of the tungsten carbide - cobalt system, in the region of interfacial boundaries, tungsten carbide, to some extent, dissolves in cobalt. The resulting compound based on tungsten carbide and cobalt has an increased fragility. The graphite interlayer at the boundary prevents these solid-phase destructive reactions. With an increase in the thickness of the graphite layer to some extent, the degree of dissolution of the components decreases. The presence of hydrogen in the region of interfacial boundaries contributes to the reaction of dissolution of tungsten carbide in cobalt, additionally creating conditions for increasing the fragility of the carbide composition. This is due to the fact that hydrogen, located at the phase boundaries, interacts with graphite, removes it from interphase boundaries due to the formation of gaseous hydrocarbon compounds and, thus, removes the conditions for limiting the composition-destructive solid-phase interactions between tungsten carbide and cobalt.

Due to these reasons, the front and rear contact surfaces of the cutting wedge formed during wear initially, due to the destructive presence of hydrogen in the structure of the hard alloy, are weakened in strength. During the aggasive interaction of the weakened contact surfaces of the cutting wedge with the processed material, detachment of individual parts of the carbide grain and cobalt layer, and in some cases of the whole carbide grain or group of carbide grains with a cobalt environment, occurs significantly at earlier stages of operation of the carbide cutting tool.

A comparison of the wear resistance of a carbide cutting tool with the hydrogen content in the composition of the oxide mass formed during its oxidation most accurately reflects the correlation between the main operational characteristic and the ability of the alloy structure to accumulate hydrogen. The oxide formations obtained at a temperature corresponding to the optimum cutting temperature in an electric furnace with open access to atmospheric air in composition and properties are as close as possible to the properties of oxide structures formed in the contact zones of a carbide cutting tool, applicability group K with the processed material, causing intense adhesion wear.

From the obtained tests, when determining the wear resistance of carbide cutting tools and determining the amount of hydrogen in the oxide mass, it also follows that thin oxide formations formed in the contact zones of the cutting and processed materials and their chemical, physical and mechanical properties have decisive effects on the thermodynamics and kinetics of tribological processes and reflect the performance of carbide cutting tools in general.

Thus, the composition of hard alloys, the state of their structure, the presence in the components of certain impurities significantly affect, on the one hand, the wear resistance of cutting tools of the applicability group K when they process materials that cause intense adhesive wear, and on the other, their ability accumulate hydrogen during their oxidation in its structure. With a decrease in the ability of the structure of a hard alloy to accumulate hydrogen and then store it in oxide, the wear resistance of carbide cutting tools increases. With a decrease in hydrogen in the structure of the hard alloy, and ultimately in the oxide, it leads to an improvement in its physical and mechanical characteristics. Fracture resistance is reduced, which is, essentially, important for the predominant action of adhesive wear in the contact areas of the cutting tool with the processed material, which is accompanied by a cyclic local force action on the contact faces. With a decrease in the structure of stored hydrogen in the contact zones, film structures formed from higher oxides are more likely to form, effectively screening intermolecular interactions and are a solid lubricant.

An essential feature of the proposed method is that in accordance with its methods - without additional costs and technical difficulties, it seems possible to conduct a more objective and accurate assessment of wear resistance - due to the operational analysis and comparison of current controlled and reference parameters obtained in a wide range of cutting conditions and temperatures cutting. The properties of carbide cutting tools of the applicability group K are greatly influenced by wear-resistant coatings. A stable correlation is also observed between the operational characteristics of carbide cutting tools and the hydrogen content in their oxide formations. And for these tool materials, the rule is observed: with a decrease in the hydrogen accumulated in the oxide structure, the wear resistance of carbide cutting tools of the applicability group K increases. Accordingly, the proposed forecasting method for evaluating their operational characteristics is also applicable.

The implementation of the method is carried out sequentially through several stages. First, carbide cutting tools (cutting inserts) are tested during cutting of materials that cause intense adhesive wear. After wear tests, the inserts are thoroughly cleaned and oxidized in an electric furnace with open access to atmospheric air at a temperature close to the temperature that occurs in the material processing zone at the optimum cutting speed. From the oxide mass formed on the surfaces of the cutting tools, we select randomly from 0.2 to 0.3 g, place them in special crucibles, and then the crucibles themselves are placed in the working chamber of the device one by one to determine hydrogen and in each case the amount of hydrogen in the oxide is determined mass. After turning on the device - a hydrogen analyzer and automatic weighing of the sample - the crucible with the sample is autonomously placed between the electrodes. Next, the sample is melted, and the weight of the hydrogen released during melting of the sample is automatically estimated by changing the thermal conductivity (electrical conductivity) of the carrier gas (argon). Then, the concentration of hydrogen in the sample of carbide is automatically calculated in units of ppm. Outcome computer also automatically calculated by multiplying the hydrogen analyzer determines the concentration per 10 ^4.

The determination of hydrogen in the structure of carbide cutting tools of the applicability group K was carried out using a LECO model RHEN602 hydrogen analyzer. The analyzer is equipped with a Windows system. The process of determining hydrogen in an oxide sample is carried out when it is melted in a stand-alone electrode furnace in a carrier gas (argon). Hydrogen concentration - the ratio of the mass of hydrogen released during the melting of the sample to the mass of the sample (sample) is estimated by recording the thermal conductivity of the carrier gas, in the atmosphere of which the sample is melted. The measurement of the thermal conductivity of the carrier gas is carried out in a thermoconometric cell. First, a graphite crucible, in which the oxide sample sample is then melted, is degassed. Degassing begins after placing an empty graphite crucible (without sample) between the electrodes and then turning on the analyzer. As a result of this, the electrodes come together, they are shorted, and the combustion mode is realized — the crucible is cleaned of atmospheric gases. At the same time, a current of 800A passes through the crucible, heating it to a high temperature, contributing to the release of gases located on the surface and in micropores of the surface region of the graphite crucible. Then, the sample measured for the presence of hydrogen is placed in the loading device, weighed and moved through the lock from the loading device into a degassed crucible. After that, a high current is again applied to the crucible, heating the crucible and the sample, while releasing gases from the melting sample. In order to prevent the possible evolution of gases from the crucible during the current working analysis, a current is supplied to the crucible, the force of which is slightly lower (600A) of the previous degassing current. The process of melting a sample in a crucible is carried out in a carrier gas. Before entering a metered amount into a thermoconometric cell with an empty crucible, and then with a crucible and a sample mounted on it, the carrier gas is thoroughly cleaned. First, gas from a gas cylinder passes through a piping system through a heated copper filter to clean it of oxygen impurities. Then the gas passes through special chemicals to clean it of CO ₂ (carbon dioxide) and H ₂ O (moisture). The process of purification of the carrier gas, and then the carrier gas with hydrogen released after the sample was melted, is carried out after the degassing mode and, accordingly, the operating mode (melting of the sample in a crucible with a carrier gas). The thermal conductivity of the carrier gas is measured in the thermoconduction cell after the crucible “degassing” mode (without the sample) and after the sample is melted in the crucible. As the sample is heated and melted (after the electrodes are closed), the released hydrogen and other gas enters the transporting gas stream and passes through the gas flow control section. The gas again passes through special chemicals that remove CO ₂ and H ₂ O (moisture). Finally, the sample gas passes through the measuring system to a thermoconometric cell, where the thermal conductivity of the carrier gas with the hydrogen released during melting of the sample is measured. Since hydrogen has a very high thermal conductivity in comparison with other gases, the content of hydrogen released during melting of an oxide sample is determined by a change in the thermal conductivity of the carrier gas (in a mixture with hydrogen released from the molten sample) with high accuracy. The data on the thermal conductivity of the carrier gas and the carrier gas with hydrogen released during melting are transferred to an analog-to-digital converter, and then to a computer processor and, finally, to a computer display.

The entire measurement process is displayed on the screen of the processor unit. Typically, the measurement time is not more than 1 min. The measurement is characterized by high reproducibility of the results, because eliminates errors associated with the selection, preparation and analysis of individual samples of oxide masses characteristic of traditional methods of analysis. The hydrogen concentration of the oxide mass of the hard alloy is determined by the computer system of the analyzer in accordance with the formula:

$$\omega =\frac{m\mathrm{but}\mathrm{from}\mathrm{from}\mathrm{but}\mathrm{at}\mathrm{about}d\mathrm{about}R\mathrm{about}d\mathrm{but},\mathrm{at}sdel\mathrm{and}\mathrm{at}weg\mathrm{about}\mathrm{from}\mathrm{I\; am}\text{when melting an oxide sample - samples}}{\text{weight of the oxide sample - samples}}\times {10}^{\mathrm{four}}(ppm)$$

The prediction of the wear resistance of carbide cutting tools of the applicability group K when they process materials that cause intense adhesive wear is that they first conduct resistance tests of carbide cutting inserts from two samples of the carbide product batch, determine the wear resistance of each carbide cutting insert, determine the average wear resistance for carbide cutting plates for each sample, produce oxidation in an electric furnace tested for resistance of carbide cutting inserts, take samples of oxide mass from oxidized carbide cutting plates, place them in the analyzer, melt the samples, determine the concentration of released hydrogen from each sample - oxide sample, determine the average values of released hydrogen for sample-samples for each sample, plot the dependence wear resistance from the concentration of released hydrogen. Then, the prediction of the wear resistance of the next delivered batch of carbide cutting inserts of the applicability group K is performed without testing them during the cutting process, but only by determining the presence of hydrogen concentration in their oxide mass obtained by oxidation of the carbide cutting insert. With a decrease in hydrogen in the composition of the oxide mass of carbide cutting inserts, their wear resistance increases when cutting materials that cause intense adhesive wear.

Moreover, to predict the wear resistance, use dependence (1) and also use the graph of the dependence "hydrogen concentration - wear resistance", obtained earlier in the test - forecasting the wear resistance of the first (reference) batches of carbide cutting inserts.

In FIG. 1 shows the reference dependence "hydrogen concentration - wear resistance", on the basis of which a forecast is made of the wear resistance of carbide applicability groups K of cutting inserts when they cut materials that cause intense adhesive wear.

Taking into account the considered features of the interaction of carbide tool materials of the applicability group K with hydrogen, it can be stated that a large number of controlled factors, such as the main ones, are used to saturate the structure of hard alloys with hydrogen, for example, the main ones: the composition of the starting materials intended to produce tungsten and cobalt powders , graphite, the presence of certain impurities, the technology for producing these powders, the technology for producing carbides, especially grinding and mechanical activation of powders, features of the sintering process of components of hard alloys, the composition of the gas medium used in the preparation of powders and their sintering.

By purposefully controlling and regulating these factors, it is possible to create conditions under which the internal structure of hard alloys will accumulate the smallest possible amount of hydrogen. This approach will ensure the formation of the most optimal structure of hard alloys in their manufacture. At the same time, with a decrease in the applicability group K of hydrogen in the mass of hard alloys, their wear resistance increases when cutting materials that cause intense adhesive wear.

An example of a method for predicting the wear resistance of carbide cutting tools. First, two batches (accepted as reference) in the amount of 10 pieces each of carbide cutting inserts of the applicability group K of the VK8 grade are tested for wear resistance on a model 163 screw-cutting lathe. The material used was Kh17N13M2T chromium-nickel steel. The cutting speed during the tests was chosen equal to 70 m / min. The feed rate and depth of cut were respectively 0.23 mm / rev and 1.5 mm. Cutting was carried out without cooling. As a blunting criterion, the wear of the insert along the rear surface, equal to 0.6 mm, was taken.

Resistance for samples of 10 pieces of the first reference batch was: 29.20; 29.00; 28.50; 27.50; 26.80; 26.50; 26.00; 25.75; 25.00; 24.40 minutes The average value was 26.865 minutes.

Resistance for samples of 10 pieces of the second reference batch was: 29.30; 28.80; 28.40; 27.80; 27.20; 26.60; 26.20; 25.90; 25.20; 24.30 minutes The average value was 26.970 minutes.

Then, the tested carbide plates after chemical cleaning in an ultrasonic bath and drying were subjected to oxidation in an electric furnace with open access to atmospheric air at a temperature of 800 ° C. After that, from the oxide mass obtained on the surface of carbide cutting inserts, weighed masses in the range from 0.2 to 0.3 g were selected and examined to determine the presence of hydrogen in their structure. The saturation of the structure of carbide cutting tools of the group of applicability to hydrogen occurred during the manufacturing of individual components and the subsequent sintering of the composite as a whole.

The mass of prepared oxide samples (pieces in a sample) obtained from the first batch tested in the process of cutting carbide cutting inserts was: 0.257; 0.263; 0.266; 0.271; 0.274; 0.279; 0.285; 0.289; 0.294; 0.297 g.

The mass of prepared oxide samples (pieces in a sample) obtained from the second batch of carbide cutting inserts tested during cutting was: 0.262; 0.265; 0.267; 0.269; 0.272; 0.275; 0.278; 0.283; 0.288; 0.296 g.

The thus prepared sample is set in a special lock chamber is placed in a degassed graphite crucible, crucible mounted between the electrodes produce melting sample, purified gas mixture of the carrier gas with the released hydrogen from carbon dioxide _(CO2) and moisture (H ₂ O), determining the thermal conductivity (electrical conductivity) of the carrier gas mixture with hydrogen liberated during combustion and, on the basis of this parameter, actually determine the mass of hydrogen. The process of determining the mass of hydrogen released, accumulated by the oxide structure, is carried out using the LECO RHEN602 analyzer in automatic mode.

The accuracy of determining the concentration of hydrogen liberated from the oxide structure of the hard alloy using this device (LECO analyzer RHEN602) is 0.02 ppm.

у оксидных образцов, полученных из первой партии режущих пластин, соответственно, составила: 0,41; 0,43; 0,47; 0,51, 0,56; 0,59; 0,63; 0,65; 0,69; 0,73. Среднее значение концентрации водорода в ppm составило: 0,567.The concentration of hydrogen in units of ppm

for oxide samples obtained from the first batch of cutting inserts, respectively, amounted to: 0.41; 0.43; 0.47; 0.51, 0.56; 0.59; 0.63; 0.65; 0.69; 0.73. The average hydrogen concentration in ppm was: 0.567.

у оксидных образцов, полученных из второй партии режущих пластин, соответственно, составила: 0,43; 0,45; 0,48; 0,53; 0,57; 0,61; 0,64; 0,67; 0,72; 0,76. Среднее значение концентрации водорода в ррm составило 0,586.The concentration of hydrogen in units of ppm

for oxide samples obtained from the second batch of cutting inserts, respectively, amounted to: 0.43; 0.45; 0.48; 0.53; 0.57; 0.61; 0.64; 0.67; 0.72; 0.76. The average hydrogen concentration in ppm was 0.586.

Based on the results obtained earlier on determining the wear resistance of carbide cutting inserts and the concentration of oxide samples of hydrogen released during melting, a graph of the dependence “wear resistance - concentration of released hydrogen” is constructed.

In FIG. Figure 1 shows the wear resistance of cutting inserts from VK8 of the applicability group K, respectively, for samples 1 and 2 during their processing of Kh17N13M2T steel on the concentration of hydrogen accumulated by their oxide structure. To predict the wear resistance of carbide cutting inserts in the subsequent current (manufactured or obtained) and intended for consumption batch of instrumental samples, only the concentration of hydrogen accumulated by their oxide structure is tested. So, for example, when predicting the wear resistance of the next batch of carbide cutting inserts of the applicability group K on an RHEN602 analyzer with a mass of oxide mounts: 0.246; 0.249; 0.254; 0.259; 0.264; 0.2268; 0.285; 0.289; 0.293; 0.296 the following hydrogen concentrations in ppm were obtained: 0.43; 0.45; 0.49; 0.53; 0.55; 0.57; 0.60; 0.65; 0.67; 0.73. The average value from the obtained data was 0.567 ppm. In accordance with the above formulas, a _e and b _{e are} determined.

and _e = -5.526; b _e = 23,736, then determine T _pt

T _pt = 26.83 min.

Thus, the predicted average wear resistance of the current batch of carbide cutting inserts was 26.83 min.

Control tests of wear resistance during cutting on a metal cutting machine showed the following wear resistance results: 30.80; 29.70; 29.30; 28.20; 27.60; 27.40; 27.00; 26.70; 26.20; 25.80 minutes The average value was 27.87 minutes.

When predicting wear resistance for the current batch of carbide tools, there is no need for expensive and time-consuming wear tests conducted on metal cutting machines. The method has a high forecast accuracy. This is due to the close correlation between the ability of the oxide mass of carbide cutting tools of the applicability group K to accumulate hydrogen in their structure and their wear resistance when cutting materials that cause intense adhesive wear. The degree of correlation between the concentration of hydrogen contained in the structure of the carbide group of applicability K of cutting tools and their wear resistance is r = 0.88. The degree of correlation between the initial parameter and the wear resistance of the cutting inserts in accordance with the prototype is r = 0.75. When comparing the data on the forecast of wear resistance obtained in accordance with the prototype, according to the proposed method, and also as a result of control experimental studies of wear resistance performed in the process of cutting austenitic steel X17H13M2T, it was found that the results obtained in accordance with the prototype differ from control tests by 15 -20%, while the results obtained by the proposed method differ only by 5-10%.

Thus, the proposed control method - predicting the wear resistance of carbide cutting tools can be used with sufficiently high economic efficiency in enterprises manufacturing or consuming carbide products.

Claims (3)

1. A method for predicting the wear resistance of carbide applicability groups of K cutting tools according to the selected initial parameter, including testing for changing the value of the initial parameter from the properties of the structure formed during the manufacturing of carbide cutting material, carrying out benchmark wear tests in the process of cutting materials that cause intense adhesive wear , at optimal or close to her cutting speed, the construction of the reference - correlation dependence " similar parameter - wear resistance "statistical control only parameter values starting from the current batch of carbide cutting tools, wear forecast for the current batch of carbide cutting tools on the basis of the relationship:

where a _E and b _E are constant coefficients:

of them:
T _PT - current wear resistance in minutes for tested carbide cutting tools from the predicted current batch of carbide products;
ω _PT - the current value of the selected initial parameter obtained by monitoring the oxide mass formed on the surface of carbide cutting tools during their oxidation from the current controlled batch of carbide products;
$$T_{E_{\mathrm{one}}}$$

and $$T_{E_2}$$

- wear resistance in minutes for two independent samples of carbide cutting tools from a reference batch of carbide products;
$${\omega }_{E_{\mathrm{one}}}$$

and $${\omega }_{E_2}$$

- average values of the values of the selected initial parameter obtained by monitoring the oxide mass formed on the surface of carbide cutting tools during their oxidation for two samples of samples from the reference batch of products, characterized in that in order to increase the accuracy of predicting wear resistance, the concentration value is used as the initial parameter hydrogen contained in the oxide mass obtained by the oxidation of carbide cutting tools, with a decrease in which the hardness wear resistance longwall cutting tools Group applicability to the increases. 2. The method according to p. 1, characterized in that as carbide cutting tools using carbide cutting inserts. 3. The method according to p. 1, characterized in that as carbide cutting tools from the reference batch use carbide cutting tools from the previous batch of purchased products.