Abstract
The results of studying the process of obtaining complex-profile elements of the substrate of mirrors of optical telescopes from reaction-sintered silicon carbide ceramics are presented. It is shown that the strength of silicon carbide ceramics depends on the dispersion of the silicon carbide powder and on the temperature of reaction sintering. An increase in the sintering temperature from 1500 to 1650 °C leads to an increase in strength by 60 MPa, and to 1800 °C – to a decrease in strength by 40 MPa. An increase in strength is explained by a decrease in free silicon and an increase in the content of secondary silicon carbide, a decrease in strength is explained by an increase in the size of carbide grains. The study of the influence of the modes of soldering of hexagonal elements to obtain a complex-profile element of the substrate of the mirror of an optical telescope on the strength of the soldered seam showed that the introduction of silicon carbide powder 7 μm in size and amorphous boron in an amount of 6 % into the solder composition based on silicon carbide has a positive effect on the strength of the soldered seam. Tests of the brazed specimens at three-point bending showed that fracture occurs along the body of the specimens being brazed, and not the brazed seam. The structure of the brazed joint depends on the composition of the braze alloy and the gap between the samples to be brazed.
Highlights
The results of studying the process of obtaining complex-profile elements of the substrate of mirrors of optical telescopes from reaction-sintered silicon carbide ceramics are presented
It is shown that the strength of silicon carbide ceramics depends on the dispersion of the silicon carbide powder and on the temperature of reaction sintering
The study of the influence of the modes of soldering of hexagonal elements to obtain a complex-profile element of the substrate of the mirror of an optical telescope on the strength of the soldered seam showed that the introduction of silicon carbide powder 7 μm in size and amorphous boron in an amount of 6 % into the solder composition based on silicon carbide has a positive effect on the strength of the soldered seam
Summary
Представлены результаты исследования процесса получения сложнопрофильных элементов подложки зеркал оптических телескопов из реакционноспеченной карбидокремниевой керамики. Что прочность карбидокремниевой керамики зависит от дисперсности порошка карбида кремния и от температуры реакционного спекания. Повышение температуры спекания с 1500 до 1650 °С приводит к увеличению прочности на 60 МПа, а до 1800 °С – к снижению прочности на 40 МПа. Повышение прочности объясняется снижением свободного кремния и увеличением содержания вторичного карбида кремния, снижение прочности – ростом размера карбидных зерен. Исследование влияния режимов пайки шестигранных элементов для получения сложнопрофильного элемента подложки зеркала оптического телескопа на прочность паяного шва показало, что положительное влияние на прочность паяного шва оказывает введение в состав припоя на основе карбида кремния порошка карбида кремния дисперсностью 7 мкм и бора аморфного в количестве 6 %. Ф. Сложнопрофильные элементы аэрокосмической техники из реакционно спеченной карбидокремниевой керамики / А.
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