INCREASING THE RESISTANCE OF PRECISION INSTRUMENT-MAKING ELEMENTS FROM OPTICAL GLASS TO EXTERNAL THERMO-INFLUENCES BY PRELIMINARY ELECTRON-BEAM PROCESSING OF SURFACES
- 1 Department of Electrotechnical Systems, Cherkassy State Technological University, Ukraine
- 2 Faculty of instrument-making, National Technical University of Ukraine "Kiev Polytechnic Institute", Ukraine
- 3 Department of organization of technogenic-prevention work and health safety, Cherkassy Institute of Fire Safety named after Heroes of Chornobyl of National University of Civil Protection of Ukraine, Ukraine
- 4 Department of Physics, Cherkassy State Technological University, Ukraine
Abstract
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.