International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The study has been carried out and experimental and statistical models have been developed to determine the critical values of external extreme action parameters (intense heat flows, times of their action, increased external pressures) on optical elements made of glass and ceramics, the excess of which leads to their surface destruction (the appearance of cracks, chips and other defects) and, ultimately, to the failure of optoelectronic devices.

An experimental study of the geometrical characteristics of the cross sections of the thermally affected areas obtained by electron beam welding of carbon steel 45 is made. The thermally affected zone and the molten area of the welds from non-stainless steels corresponds to a zone where the physical-mechanical properties and the microstructure of the processed material are changed after the processing. The process parameters that were changed during the experiments are: welding speeds were 0.5, 1.0 and 1.5 cm/sec, the beam current was changed in the range of 30 – 133 mA and the focus position was changed from 72 mm above the sample surface to 62 mm below the sample surface. The accelerating beam voltage was 50 kV. The geometry of the weld in the cases of a deep penetrating electron beam and narrow thermally affected zone is investigated. Electron beam welding process parameter optimization is performed, based on the estimation of regression models. In such way the electron beam optical systems can be tested and the specific quality requirements for the welds obtained by electron beam welding can be fulfilled

Existing experimental researches show that in order to prevent the destruction of optical elements of modern opto-electronic devices (discs as the light filter linings for IR devices, the input protective windows of laser sighting systems for observation in IR areas of the spectrum, semispherical fairings of IR devices for homing and observation of objects, lightguides for laser medical devices, etc.), electron beam method becomes promising, as it provides cleaning of surfaces, increases their microhardness, makes them more resistant to external influences. The results of experimental studies to improve the properties of the surface layers of elements from optical ceramics after their processing with a moving electron beam with a heat density Fn = 106…1.6∙107 W/m2 and moving speed V = 10-3…10-1 m/s (increase in the surface microhardness from 1.2 … 2.9 GPa (raw elements) to 5.7 … 6.4 GPa (processed elements), the occurrence of hardened layers with a thickness of 210… 230 microns). It has been established that the improvement of these properties leads to an increase in the resistance of elements to external thermal effects: an increase of 1.3…1.7 times the critical values of external heat flows and their exposure times, exceeding which leads to the destruction of elements and the failure of devices for the studied range of change of external pressure is 105…107 Pa; increasing the maximum allowable values of thermoelastic stresses in elements from 50…140 MPa to 160…370 MPa at heating temperatures of 300…1200 K.

It is determined, that electron-beam processing of elements from optical glasses with nanosized coatings from metal oxides leads to improvement of their physical and mechanical properties, that influence operational characteristics of elements: negative microdefects on the surface are excluded, its microporosity decreases by 5… 10%, as well as microroughness from 30… 35 nm to 9… 15 nm; the microhardness of the surface increases from 2,3…3,5 GPa to 23,7…24,9 GPa, thus the influence of the coating thickness on its value decreases by 30…40%; wear resistance increases by 7… 12% and service life of optical elements increases by 20… 30%. Mathematical model has been developed, allowing to pre-define critical modes of electron-beam processing of elements, control of which allows to prevent their possible destructions and increase the probability of nonfailure work at operation.

The range of parameters of the electron beam (density of thermal effect Fn = 7∙106…8∙108 W/m² and travel speeds V = 5∙10-3…5∙10-2 m/s), within which there is an improvement in the performance characteristics of optical elements: increase of microhardness of the surface of elements from optical ceramics from 1,21∙103…2,83∙103MPa to 4,84∙103…7,15∙103 MPa and increase of the spectral transmission coefficient of IR-radiation by 4… 6% for elements of optical glass and for 5… 7% – for elements of optical ceramics; there occurs an increase in the critical values of the external heat flow leading to the destruction of the elements by 1,5…2 times, thus the increase of external pressure up to 107 Pa decreases the specified critical values by 1,3…1,5 times; critical values of thermoelastic stresses in optical elements at heating temperatures 300… 1200 K increase by 1,5…2,5 times, indicating an increase in resistance to thermal effects and increased external pressures of optical elements processed by an electronic beam; the values of critical heights of falling of a steel ball on their surface, leading to destruction of elements, increase from 0,18…1,1 m to 0,37…1,35 m, so, their resistance to mechanical shocks increases. It is established, that increase of durability of optical elements, processed by an electron beam, to external thermal and mechanical effects leads to the increase of probability of non-failure operation of optic-electronic devices under extreme conditions of operation to 10… 20%.

The results of experimental studies to improve the properties of the surface layers of the elements of optical glass (K8, K108, 6 8 2 K208, BK10, TF110) after their processing by mobile electron beam with density of heat exposure F = 7·10 …8·10 W/m and n -3 -2 displacement speed V = 5·10 …5·10 m / s (a reduction of residual microroughness height at the surface from 4 … 6 nm (unprocessed elements) to 0.5 … 1 nm (processed elements), the occurrence of melted layers of thickness up to 250 … 300 microns with a modified structure, which is close to the quartz glass) are presented. It was found that the improvement of these properties increases the resistance of elements to external-heat: an increase in 1.3 … 1.7 times of the critical value of external heat fluxes and the time of their exposure, the excess 5 7 of which leads to the destruction of elements and damage to the test instrument turndown external pressure 10 …10 Pa; increasing the maximum permissible values of thermal stress in the elements from 20 … 40 MPa to 90…100 MPa heating temperatures 300 … 1200 K;an increase of the probability of failure-free operation in the 2 … 2.5 times by increasing the speed of the external heating from 100 K / s to 400 K / s.

The results of experimental studies of the influence of electron beam parameters (density of heat action, the speed of movement) on the properties of the surface layers of the elements of optical ceramics (changes in the structure of the material through the thickness of the element, the amount of surface microhardness, values of residual thermal stresses in the layers, the thickness of the hardened layers, their stability to external thermal and mechanical stresses) are. The optimum range of parameters of the beam, within which there is improvement in the properties of the surface layers of the optical elements, which leads to the increase of the basic technical-operational characteristics of devices based on (reliability, lifetime) in the conditions of use of devices with the influence of external-heat are established.

The formation features of transition metals borides at high temperatures and low pressures were investigated and discussed the conditions of formation, structure and wear properties of boride layers on the surface, formed in electron beam processing in a vacuum.

The saturation of the surface layers of metals and alloys boron is conducted with the purpose of increase of their surface hardness, wear resistance, etc. Multicomponent layers containing in its composition borides of refractory metals, as a rule, formed by the methods of chemical-thermal processing in the interaction boriding component with refractory or by saturation boron refractory impurities metal or alloy.

In this work, we studied the features of formation of vanadium and iron borides on the surface of instrumental steels U8A and R18 under the influence of intense electron beams in continuous and pulse modes.

The usage of the high-energetic source of the electron beam enables a repeated surface quenching of the chosen areas of an engineering part surface. Different techniques of the electron beam deflections allow the creation of hardened layers of different shapes and above all the thicknesses. The deflection was tested at one point, six points, a line and a field on the material 42CrMo4 (1.7225). The effect of the process speed and defocusing of the electron beam was studied. The electron beam surface quenching resulted in a very fine martensitic microstructure with the hardness over 700 HV0.5. The thickness of the hardened layers depends on the type of deflection and depends directly on the process speed. The maximum observed depth was 1.49 mm. The electron beam defocusing affects the width of the hardened track and can cause an extension of the trace up to 40%. The hardness values continuously decrease from the surface to the material volume.

The optimal parameters of the ranges of the electron beam are found (heat density, velocity, displacement), within which there is improvement of the physical and mechanical properties of surface layers of optical elements: there is no formation of negative defects on their surfaces which become atomically smooth (residual microscopic ridges do not exceed 0.5… 1.5 nm); the microhardness of the surface increases, hardened layers are formed with compressive stresses. This leads to the reduction of the light scattering coefficient of surface layers of elements and increase of their coefficient of infrared radiation transmittance and, ultimately, to the improvement of metrological characteristics and reliability of devices under intensive external thermal action.

The results of experimental studies to improve the properties of the surface layers of the elements of optical glass (K8, K108, K208, BK10, TF110) after their processing by mobile electron beam with density of heat exposure Fn = 7·10⁶…8·10⁸ W/m² and displacement speed V = 5·10^-3…5·10^-2 m/s (a reduction of residual microroughness height at the surface from 4 … 6 nm (unprocessed elements) to 0.5 … 1 nm (processed elements), the occurrence of melted layers of thickness up to 250 … 300 microns with a modified

structure, which is close to the quartz glass) are presented. It was found that the improvement of these properties increases the resistance of elements to external-heat: an increase in 1.3 … 1.7 times of the critical value of external heat fluxes and the time of their exposure, the excess of which leads to the destruction of elements and damage to the test instrument turndown external pressure 10⁵…10⁷ Pa; increasing the maximum permissible values of thermal stress in the elements from 20 … 40 MPa to 90…100 MPa heating temperatures 300 … 1200 K; an increase of the probability of failure-free operation in the 2 … 2.5 times by increasing the speed of the external heating from 100 K / s to 400 K / s.