PSI - Issue 71

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

128

corrosive glass environment. The design and fabrication of the specimen, test setup and experimental procedures are discussed in subsequent sections. 1.1. Design and fabrication of tensile specimen and test fixtures Specimens have been machined from hot-rolled plates of alloy 690 material of 10 mm thickness. Chemical composition of the material was evaluated using ASTM E 3047:2016. The final composition of alloy 690 plates used for fabrication of various specimen is shown in Table 1. Table 1: Chemical composition of alloy 690 material used for the tensile tests. Material Nickel Chromium Iron Carbon Silicon Manganese Sulphur Copper Alloy 690 61.5 28.8 8.993 0.025 0.22 0.254 0.003 0.164 The tensile specimen was designed according to ASTM E-8 standard. Thickness of the specimen was around 3 mm, that is obtained from 10 mm thick plates of alloy 690 material. Total height of the smooth specimen is around 90 mm and gauge length is 19 mm. The gauge section area is around 3x4 mm 2 . The design details of the specimen is shown in Fig. 2(a). The tensile specimens were exposed using the test fixtures as shown in Fig. 2(b). The glass powder was filled in the jacket provided in the fixture after placing the specimen. The length of the jacket is around 40 mm that is used for exposing the whole gauge section inside the glass melt. The pin, cap, and attachment were made up of Inconel 625 material in order to sustain high temperature stress and corrosive environment.

(a) (b) Fig. 2: (a) Geometrical details of the tensile specimen (all dimensions are in mm); (b) Half section view of test fixture for conducting exposure to glass melt of alloy 690 tensile specimen. 1.2. Composition of glass matrix used for the study Borosilicate glass was used for exposing the alloy 690 specimen and the glass is formed as per the specification given in Kaushik et al. (2006). The glass was taken from the WIP at BARC in the form of balls of around 3 mm diameter. This was crushed and volatile gases were removed by heating the glass at 800 °C. Further, the solidified glass was crushed into powder form and then compacted inside the test fixture before loading onto the machine. The chemical composition of the glass is shown in Table 2. 1.3. Test matrix for determining the effect of molten glass environment Tests were conducted in air and molten glass environment after exposure of alloy 690 specimen for different time, stress and temperature. The stress levels of exposure were chosen by carrying out the stress analysis of melter pot assembly under actual plant operating conditions. It was observed that some stress concentration zones are formed at the interface of glass matrix and glass melt. Since different temperature may arise during its operation, the test temperature selected for conducting this study is 800 °C and 900 °C. The stress at these temperature were chosen to maintain a constant σ appl /σ y of around 0.25. The stress level at 800 °C and 900 °C are 30 MPa and 20 MPa respectively. The time duration was varied from 24 hrs to 95 hrs at 900 °C. For estimating the effect of temperature, same exposure duration of around 95 hrs was carried out at 800 °C. To isolate the effect of applied stress without the influence of the glass environment, a test was conduct ed at 900 °C under a stress level of 20 MPa for 95 hours in an air environment.