科研之友
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摘要
Silicon carbide is recommended for applications in energy technology due to its good high-temperature corrosion resistance, mechanical durability, and abrasion resistance. The prerequisite for use is often the availability of suitable technologies for joining or sealing the components. A laser-induced process using fillers and local heating of the components represents a possible low-cost option.
Investigations in which yttrium aluminosilicate glass was used for laser-induced brazing of SiC components of varying geometry are presented. A four-point bending strength of 112 MPa was found for these joints. In burst tests, laser-joined components were found to withstand internal pressures of up to 54 MPa.
Helium leak tests yielded leak rates of less than 10(-8) mbar l s(-1), even after 300 h at 900 degrees C. In contrast, the assemblies showed an increased leak rate after annealing at 1050 degrees C.
The short process time of the laser technique - in the range of a few seconds to a few minutes - results in high temperature gradients and transients. SEM analysis showed that the filler in the seam predominantly solidifies in a glassy state. Crystallization occurred during later thermal loading of the joined components, with chemical equilibrium being established. Differences in seam structures yielded from different cooling rates in the laser process could not be equalized by annealing.
The results demonstrated the long-term stability of laser-brazed SiC assemblies to temperatures in the range of glass transformation (900 degrees C) of the yttrium aluminosilicate filler. In technological investigations, the suitability of the laser joining technique for sealing of SiC components with a geometry approximating that of a fuel element sleeve pin (pin) in a gas-cooled fast reactor was proven.
- 出版日期2013-11
