PSI - Issue 71

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

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constant loading at elevated temperatures. It depends on factors such as temperature, stress level, and microstructural characteristics, necessitating a comprehensive understanding of the mechanisms dictating creep deformation. Creep resistance is a critical property for materials used in high-temperature environments, such as turbine blades in jet engines or components in gas turbines. Understanding the behaviour of materials like Su-263 under creep conditions is crucial for ensuring the reliability and safety of engineering components operating in high temperature environments. Superalloy Su-263 achieves its outstanding creep resistance through a combination of chemical composition and microstructural features. Its alloying elements, such as chromium, cobalt, and molybdenum, contribute to a stable matrix that resists deformation. Additionally, Su-263 often contains precipitation-hardening elements like aluminium and titanium, which form stable intermetallic phases that further enhances its strength and stability at high temperatures (Zhao et al. 2001). The microstructure of Su-263 typically consists of a face-centred cubic (FCC) γ matrix with a secondary phase known as ordered γ', which plays a crucial role in impending the dislocation movement. This impedes the creep process, ensuring that the material maintains its mechanical integrity under long term stress and heat exposure (Zhao et al. 2001). One of the methods employed to study creep behaviour is small punch creep (SPC) testing. SPC is a non-destructive in terms of structural integrity of in-service component and cost-effective technique used to evaluate the creep properties of materials using miniature specimens subjected to a load at elevated temperatures. Conventional tensile creep test uses larger sample which makes it difficult to employ for in-service components and high-performance exotic alloys. This method provides valuable insights and faster data generation compared to traditional methods giving the creep behaviour of materials, including parameters such as creep rate, rupture time, and minimum creep rate. SPC has emerged as a valuable tool in materials science and engineering for characterizing the creep resistance of various alloys and assessment of different zones of welded parts. In this paper, the creep behaviour of Su-263 alloy is studied using small punch creep (SPC) testing method. Additionally, it seeks to investigate the effect of load on creep life in Su-263. By studying the creep properties of Su-263 under loading of various samples at various loads and fixed temperature conditions, it evaluates the fraction of time elapsed in percentage of life with increasing load. The nickel-base superalloy Su-263 (UNS N07263/W. Nr. 2.4650) was procured from the Gas Turbine Research Establishment (GTRE), Bengaluru in s olution heat treated condition at temperature of 800 ⁰C for 8 hrs and then Air cooled. The chemical composition of the Su-263 is given in Table 1. Table 1. Chemical composition (wt %) of Su-263 Ni Cr Co Mo Ti Fe Al C B Bal. 20.00 18.90 5.80 2.16 0.50 0.45 0.06 0.0018 2.2. Sample preparation The Su-263 material procured from GTRE was taken for uniform cylindrical grinding to reduce it to 8 mm diameter. This uniformly grinded cylindrical sample (Fig.1 a) was cut into slices of thickness 0.7 mm ± 0.05 using wire cut EDM (Fig.1 b) and sample prepared according to the EN standard ECISS/TC101/WG1 for the SPC (Bruchhausen et al. 2018). These slices were polished by 800 to 3000 grit abrasive paper on both sides to get thickness of 0.5 mm (Fig.1 c) with an accuracy of ± 0.003 mm. The step-by-step procedure of sample preparation is shown in flowchart which can be seen in Fig. 1. 2. Material, sample preparation, and experiments 2.1. Material