RU2621245C1 - Method for laser processing cutting inserts made of oxide-carbide ceramics - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method for laser processing the cutting inserts made of oxide-carbide ceramic TiC+MgO+Al₂O₃, in which the surface of the cutting insert is subjected to the pulsed laser exposure, each pulse train forms a laser beam spot with a certain beam power on the sample with the laser beam spot overlapping ratio in the range of 0.1 to 0.9. Processing is carried out with a pulse repetition rate of 90 to 110 kHz, the number of pulses in the train is more than 60, and the beam power on the sample is of 7 to 8 W. Optimally, when the surface of the cutting insert is subjected to the pulsed laser exposure with the laser beam spot overlapping ratio in the range of 0.5 to 0.75.

EFFECT: increasing the durability of the cutting inserts.

2 cl, 9 dwg

Description

The invention relates to the tool industry, and in particular to methods of processing cutting inserts of oxide-carbide ceramics (ceramics based on TiC + MgO + Al ₂ O ₃ ).

The processes of abrasive processing of ceramics with a diamond tool have some technological limitations, which are manifested in the fact that a defective layer is formed on the ceramic surface after grinding, which is prone to brittle fracture under operational loads. A promising technological process capable of controlling the state of the surface layer of ceramics in order to increase the physicomechanical properties is laser modification. The essence of the laser modification process is the formation on the ceramic surface of a fine-grained structure consisting of micro-sized, optimal-nanoscale formations.

A known method of forming on ceramic substrates the structural formations of nano and micro sizes. The method includes the deposition of particles of a substance from the gas phase using local heating of the deposition region by laser radiation. The substance in the gas phase is dispersed in the form of an aerosol. Localization of the deposition region by laser pulse radiation is carried out and aerosol particles are sintered to the substrate. The duration of the laser pulse is not less than that at which the thermal wavelength in the particle is greater than the particle size in the direction of radiation. The known method demonstrates high coating performance while maintaining high resolution (patent RU No. 2452792 C2, C23C 4/12, V23K 26/14, 05/31/2010).

The disadvantage of this method is the increase in the technological chain and the cost of the process by creating an additional coating on the surface of the ceramic material. It is economically feasible not to apply the coating, but to manage the surface layer in a controlled manner based on the material from which the part is made, bypassing the intermediate technological stages.

The known method and installation for laser surface treatment of glass (glass ceramics). The method includes laser irradiation of a glass-ceramic plate and its subsequent cooling, characterized in that the plate is preheated to a temperature of 450-1100 ° C, the treatment is carried out, the sample is cooled to a temperature of 150-200 ° C together with the furnace, the final stage of cooling is carried out in air. The processing is carried out on a laser processing machine for the surface of a glass containing a CO ₂ laser, a mirror system, a focusing lens, a control computer, a desktop with a sample, a sample heater controlled by a shutter located horizontally between the focusing lens and the heater, a screen with holes located between the shutter and the sample, a blower placed between the lens and the surface of the sample, an optical system for scanning the beam along the surface of the sample (patent RU No. 2463267 C2, C0 3C 17/04, B23K 26/36).

The disadvantage of this method is that it is used to improve the properties of ceramic and is unacceptable for processing oxide-carbide ceramics (TiC + MgO + Al ₂ O ₃ ), which has a lower thermal conductivity and a high temperature coefficient of linear expansion, as well as the presence of additional thermal operations and equipment in the form of a heater.

The closest in technical essence to the claimed technical solution is the selected as a prototype method of laser processing of cutting inserts from solid non-metallic materials, including oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ , in which the working sections of the surface of the cutting insert are subjected to pulsed laser irradiation, each burst of pulses of which forms a laser beam spot with a certain beam power on the sample, with a laser beam spot overlap factor in the range from 0.1 to 0.9 (RU patent 2394 780 C1, C03B 33/00, 04/13/2009).

The disadvantages of the prototype is the following:

- the prototype method solved only the problem of shaping the product without the connection of this process with the functional state of the surface layer;

- the values and / or criteria for selecting the optimal technological processing modes are not defined, in particular with respect to the pulse power, pulse repetition rate, and the number of pulses in a packet.

The objective of the present invention is to provide the possibility of processing cutting inserts made of oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ in modes that optimally modify the treated surface according to the criterion of durability of the treated cutting inserts.

EFFECT: increased resistance of cutting inserts.

The problem is solved, and the claimed technical result is achieved by the fact that in the method of laser processing of a cutting insert of oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ , in which the surface of the cutting insert is subjected to pulsed laser irradiation, each pulse packet of which forms a laser beam spot with a certain power of the beam on the sample, with a coefficient of overlap of the laser spot in the range from 0.1 to 0.9, the processing is carried out with a pulse repetition rate of 90 to 110 kHz, the number of pulses in a packet of more than 60 and generality of the beam on the sample of 7 to 8 W, optimally, when the surface of the cutting insert is subjected to pulsed laser irradiation from a laser beam spot overlap ratio in the range from 0.5 to 0.75.

The invention is illustrated by drawings, where:

- in FIG. 1 shows a laser unit with its constituent elements ( a ) and processing scheme (b);

- in FIG. 2 shows a plate with a machined surface area for abrasion resistance tests;

- in FIG. 3 shows a laboratory bench for tribological tests for wear resistance during friction with its constituent elements;

- in FIG. 4 shows an example of measuring the width of a wear section after friction by a disk;

- in FIG. Figure 5 shows the effect of the pulse repetition rate at various values of the beam power on the sample on the width of the friction wear section;

- in FIG. Figure 6 shows the effect of the number of pulses in a packet at various values of the beam power on the sample on the width of the friction wear section;

- in FIG. 7 shows the effect of the overlap coefficient of the laser beam spot at different values of the beam power on the sample on the width of the friction wear section;

- in FIG. 8 shows micrographs of the surfaces of oxide-carbide ceramics after diamond grinding ( a ), fracture of the initial ceramic (b), after laser modification (c and d) in the rational regime of laser radiation;

- in FIG. Figure 9 shows the wear – time relationships for turning steel ШХ15 (55 HRC) with cutters with plates from the original ceramic (1) and ceramic with a modified surface layer (2) at ν = 125 m / min, S = 0.05 mm / rev and t = 1 mm ( a ); at ν = 150 m / min, S = 0.05 mm / rev and t = 1 mm (b); ν = 150 m / min, S = 0.075 mm / rev and t = 1 mm (in); ν = 150 m / min, S = 0.1 mm / rev and t = 1 mm (g).

The optimal modes of the method were determined during the experiment, in which the working sections of the cutting insert, including the front and rear surfaces, as well as the hardening facet, were subjected to pulsed laser irradiation. Optimum processing conditions were determined by the results of tests of machined cutting inserts for wear resistance during friction.

The experimental processing of the plates was performed using a technological laser mode. U-15 (RMI Laser LLC (USA), having a solid-state source based on an Nd: YVO ₄ crystal with a wavelength of λ = 1064 nm, a pulse duration of τ = 7 ns, and a radiation frequency of 10 kHz. The processing field has an area of 100 × 100 mm . by setting the optimum focal distance of the lens 163 mm provided focusing spot diameter d _f = 40 mm. The laser system consists of the head unit 1, the control of the controller 2, the working surface 3 and the focusing lens 4 (Fig. 1 a). The laser beam is moved in two coordinates (x and y), and initially created a track along the x coordinate, then the beam ne moved along the y coordinate and created the next track. Due to these successive movements, the processed area was formed (Fig. 1b). The practical implementation of this processing scheme provides the choice of the values of the overlap coefficient of the laser beam spot k _p with unchanged d _p = 40 μm.

Technological modes of pulsed laser exposure were varied in the ranges: the beam power on the sample from 1 to 15 W, the pulse repetition rate from 10 to 170 kHz, the number of pulses in a packet from 1 to 75 pulses, the overlap coefficient of the laser beam from 0.1 to 0, 9. The immutable, constant parameters were the relative scanning scanning speed (ν = 100%) and the diameter of the focusing spot d _p = 40 μm. On the end surface of the samples of ceramic plates with a size of 12.7 × 12.7 formed the area of 10 × 10 mm (Fig. 2).

The surface structure of the samples processed during the experiment was studied using a VEGA3 LMH scanning microscope, whose software allows measurements of the width, height, diameter, and area of grains. To identify the optimal technological regimes of pulsed laser exposure, the samples were tested for wear during friction. Based on the study of normative literature, the most rational scheme of dry friction was chosen - “fixed sample - rotating disk”.

The friction scheme was implemented at the laboratory bench. Design features of the stand are shown in FIG. 3.

The base 1 of the stand is stationary attached to the support 2 of the lathe, which allows you to accurately orient the contact area using the flywheels of the longitudinal and transverse movement of the support. An axial support 3 is mounted on the base, onto which an equal-arm lever 4 is mounted. A vice 5 is mounted on one edge of the lever with a ceramic specimen fixed in them, and a load 6 with an estimated weight is freely suspended, under which a ceramic specimen with a set force F _{n is} pressed against rotating disk 7. The disk is mounted on a mandrel 8, mounted in a turning chuck 9, to ensure rigidity, the mandrel is pressed by the rear center 10.

An analysis of the results made it possible to identify the width of the wear section (h _of ) on samples having an initial and modified surface. In FIG. 4 shows an example of measuring the width of a wear section.

The effect of the pulse repetition rate at various values of the beam power on the sample on the width of the friction wear section is illustrated in FIG. 5. It was found that the smallest value of h _from for all values of the beam power on the sample was recorded at a pulse repetition rate in the range from 90 to 110 kHz. The minimum value of h _{from was} noted at a beam power on the sample between 7 W and 8 W (7.5 W).

The effect of the number of pulses in a packet at different values of the beam power on the sample on the width of the wear section is illustrated in FIG. 6. It was found that with an increase in the number of pulses in a packet from 60 pulses or more, the width of the wear section decreases rapidly at all values of the beam power on the sample. The minimum value of h _{from was} noted at a beam power on the sample of about 7.5 watts.

The effect of the overlap coefficient of the laser beam spot at different values of the beam power on the sample on the width of the friction wear section is illustrated in FIG. 7. It was found that the smallest value of h _from for all values of the beam power on the sample was recorded at a spot overlap coefficient k _p from 0.5 to 0.75. The minimum value was noted at a beam power on the sample of 7.5 watts.

It has been established that rational laser radiation conditions according to the criterion of the minimum value of the friction wear section are: pulse repetition rate from 90 to 110 kHz, number of pulses in a packet over 60, beam power on a sample from 7 to 8 W and spot overlap coefficient from 0.5 up to 0.75. Subject to the specified set of modes, a decrease in the wear parameter by 24% is recorded in comparison with the polished surface of the oxide-carbide ceramic plate.

In FIG. 8 shows micrographs of the surface of oxide-carbide ceramics after diamond grinding (Fig. 8 a ) and after laser modification (Fig. 8b and d) in a rational regime of laser radiation.

On the polished surface (Fig. 8 a ), a loose defective layer formed by plastically deformed grains, pores of various shapes is marked, grains up to 2.8 microns in size are visible in the inner pore volume. After laser treatment, the surface layer is formed by uniform particles of crushed ceramic grains of irregular geometric shape. The range of particle size ranges from 0.3 to 2.2 microns. The boundaries between the particles are dense, the surface has a smooth relief without sumps and protrusions. The absence of scaly structures on the surface indicates that the surface layer was not intensively fused, cracks and pores are absent. The described features of the surface layer allow us to talk about the implementation of the laser modification mechanism.

Using rational modes, an experimental batch of plates was made and tested for wear resistance during turning. According to the results of research tests for wear resistance during turning, it was found that the highest average resistance when turning steel SHX15 (55 HRC) at a speed of 125 m / min, a feed of 0.05 mm / rev and a cutting depth of 1 mm have cutters with polyhedral non-turning plates with a modified surface layer (Fig. 9 a ). So, with longitudinal turning, the average resistance of plates with a modified surface layer with a blunting criterion of h _s = 0.5 mm was 12% higher than that of the original plates. T _cf = 43 min and 38 min, respectively. At ν = 125 m / min, S = 0.05 mm / rev and t = 1 mm, cases of the initial and modified plates getting out of working condition due to brittle fracture (chips) have not been established.

An increase in cutting speed to 150 m / min also revealed the operational advantages of cutting inserts with a modified surface layer compared to the original inserts (Fig. 9b). So, the average resistance of plates with a modified surface layer was 31 min, of the initial plates 24 min, respectively. The excess of resistance was 29%. At ν = 150 m / min, S = 0.05 mm / rev and t = 1 mm, cases of the exit of the initial and modified plates from a working state due to brittle fracture (chips) have not been established.

When the operating conditions are tightened (increase in feed value), the increase in the working capacity of ceramic inserts with a modified layer in comparison with the original inserts is also obvious (Fig. 8 c and d). So, for ν = 150 m / min, S = 0.075 mm t = 1 mm and ν = 150 m / min, S = 0.1 mm t = 1 mm, the average resistance of the initial plates was 11 and 5.8 min, modified plates 18 and 12 min, respectively. Moreover, the analysis of plate failures showed that 45% of the initial plates failed due to brittle fracture, a similar indicator of plates with a modified surface layer was 28%. The decrease in standard deviation of resistance 5 was 2.2 times.

The foregoing allows us to conclude that the objective of the invention is to provide the possibility of processing cutting inserts made of oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ in modes that optimally modify the treated surface according to the criterion of durability of the processed cutting inserts - solved, and the claimed technical the result - increased durability of the cutting inserts - is achieved.

The analysis of the claimed technical solution for compliance with the conditions of patentability showed that the characteristics indicated in the independent claim are essential and interconnected with each other with the formation of a stable set of necessary features unknown at the priority date from the prior art sufficient to obtain the desired synergistic technical result.

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed technical solution:

- the object embodying the claimed technical solution, when implemented, relates to the tool industry, and in particular to methods of processing cutting inserts from oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ ;

- for the claimed object in the form described in the formula below, the possibility of its implementation using the methods and methods described above or known from the prior art on the priority date is confirmed;

- the object embodying the claimed technical solution, when implemented, is able to ensure the achievement of the technical result perceived by the applicant.

Therefore, the claimed subject matter meets the requirements of the patentability conditions of “novelty”, “inventive step” and “industrial applicability” under applicable law.

Claims (2)

1. A method of laser processing a cutting insert made of oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ , wherein the surface of the cutting insert is subjected to pulsed laser irradiation, each burst of pulses of which forms a laser beam spot with a certain beam power on the sample, with a spot overlap coefficient a laser beam in the range from 0.1 to 0.9, characterized in that the processing is carried out with a pulse repetition rate of from 90 to 110 kHz, the number of pulses in a packet of more than 60 and the beam power on the sample from 7 to 8 watts. 2. A method of laser processing a cutting insert made of oxide-carbide ceramic TiC + MgO + Al ₂ O ₃ according to claim 1, characterized in that the surface of the cutting insert is subjected to pulsed laser irradiation with a coefficient of overlap of the laser spot in the range from 0.5 to 0 , 75.

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