PSI - Issue 71

Pramod Ravindra Kushwaha et al. / Procedia Structural Integrity 71 (2025) 74–81

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D = 8mm

t = 0.5mm

(b) Circular Disc ( ⌀ 8mm, t = 0.7mm)

(a) Cylindrical sample ( ⌀ 8mm)

(c) Polished Samples on different grate papers ( ⌀ 8mm, t = 0.5mm)

(d) Final SPC disc specimen

Fig. 1. Sample preparation steps for SPC testing

2.3. Small punch creep testing

The SPC 1000 DLS machine (make: UTM) was used to perform the small punch creep test that has the load capacity of 4 kN. The system comprises of a loading unit (Load cell), displacement measuring device, furnace, sample holder, silicon nitride (Si 3 N 4 ) spherical ball of 2.38 mm diameter and a data recorder. In order to avoid oxidation of the specimen due to high temperature, the specimen chamber was thoroughly flushed and rinsed with argon gas and its flow was continuously maintained throughout the experiment. The SPC tests were conducted in constant load mode as it was done by other researcher on P92 Steel (Deshmukh et al. 2016). The specimen was held in a specimen holder and load was applied by means of silicon nitride ball through the mandrel connected to load cells composed of a linear actuator coupled with a servo motor.

Fig. 2. Schematic representation of small punch creep test setup The schematic diagram of SPC setup is shown in Fig. 2. The similar setup was also depicted by S. Arunkumar and H.K. Al-Abedy (Al-Abedy et al. 2018, and Arunkumar 2021) in their study. The displacement was measured by means of a pulse encoder type displacement measuring device in the range of 0 – 5 mm. The SPC tests were conducted on Su-263 at temperature of 650 °C under different load levels in the range of 650 – 750 N and tests were continued till displacement reached the value of 2.5 mm. 4. Results and Discussion 4.1 Microstructural characterization The microstructure of as received sample using optical microscope (Model: Axioskop 2Mat and Make: Zeiss) is depicted in Fig. 3 (a). In optical micrographs it has been seen that the Su-263 samples exhibit a higher concentration of M 23 C 6 -(Cr,Mo) 23 C 6 and M 6 C-(Co, Ni) 3 Mo 3 C precipitates within the grains (Zhao et al. 2001). From scanning electron micrographs of as received material in Fig. 3(b), a fine M 23 C 6 particle also form intragranularly and fine