PSI - Issue 71

P.K. Sharma et al. / Procedia Structural Integrity 71 (2025) 126–133

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The details of the test matrix used for determination of the effect of molten glass environment on mechanical properties of alloy 690 material is shown in Table 3. Table 2: Chemical composition of borosilicate glass used for exposure of alloy690 specimen. Material Boron Silicon Iron Zinc Sodium Titanium Borosilicate glass 6.4 10.3±0.8 8.69 0.16 17.83 0.1 Table 3: Test matrix used for evaluation of effect of molten glass environment on mechanical properties of alloy690 material. Test environment Temperature (°C) Stress level (MPa) Exposure duration (hrs) Air (Reference tests) 800 - - 900 - - Air (Under stress) 900 20 95 Molten glass 800 30 95 900 20 24, 48, 95 1.4. Experimental procedure The tests were performed in both air and molten glass environments on alloy 690 specimens. The universal testing machine can operate at temperatures up to 1200 °C, with a control range of ±2 °C. It has a load control capacity of ±50 kN and features a servo-based control system. The glass powder was compacted onto the test fixture and loaded on the machine attachment. A split-type furnace with three-zone control was utilized to achieve the desired temperature. Once the target temperature was reached, the specimens were held for a minimum of one hour to ensure thermal equilibrium with the surroundings. During this period, the specimens were maintained under zero load using an inbuilt software program to prevent any loading effects due to thermal expansion. Additionally, water circulation was employed to cool the fixtures and protect external electronics from overheating. Fig. 3(a) shows the machine used for these tests. The specimens were then exposed to the molten glass/air environment for the specified exposure duration. The deformation of the specimens under constant stress was kept minimal compared to their total ductility. Once the desired exposure time was reached, a tensile test was conducted in constant displacement mode at a rate of 0.5 mm/min, continuing until the specimen ruptured. Data on displacement, stress, strain, and temperature were recorded for further post-processing. After the tests, the specimens were removed from the machine fixtures for microstructural analysis. Fig. 3(b) shows the specimens tested in air, while Fig. 3(c) presents those tested in molten glass. Notably, a layer of glass is observed on the tensile specimens post-test, indicating that the molten glass fully covered the gauge region of the Alloy 690 specimens.

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Fig. 3: (a) Machine used for the tests; (b) Specimen before and after test in air environment at 900˚C (c) Specimen after tes t in molten glass environment at 900˚C. 3. Stress-strain response of alloy 690 material under different test conditions The tensile tests were carried out in order to determine the effect of molten glass environment on mechanical properties of alloy690 material. The tests were carried out in air environment (Reference tests) and molten glass