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Investigating Hot Fracture Mechanism of MP210 Superalloy at High Temperature

Habibi, Mohammad Hossein | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57154 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Asgari, Sirous
  7. Abstract:
  8. The MP210 superalloy belongs to the category of multi-phase superalloys, designed for specific applications at high temperatures, such as components in gas turbine engines. However, its usage is limited due to hot fracture concerns at temperatures around 800 degrees Celsius. This research delves into the mechanism of hot fracture in this alloy. To explore this, the microstructural changes in samples subjected to hot tensile testing in the temperature range of 500 to 1000 degrees Celsius were studied using microscopic and microanalytical techniques. The yield strength and ultimate tensile strength at 500 degrees Celsius were 475 and 850 megapascals, respectively, decreasing to 105 megapascals each at 1000 degrees Celsius. The percentage of elongation and reduction in cross-sectional area decreased from 55% and 48% at 500 degrees Celsius to 11% and 12% at 800 degrees Celsius. At 950 and 1000 degrees Celsius, these percentages increased to 21% and 54%, indicating a reduction in ductility attributed to the SAGBO phenomenon. The results revealed the formation of two phases, γ' and η, in the alloy at temperatures approximately ranging from 750 to 900 degrees Celsius. The occurrence of the SAGBO mechanism between 800 and 900 degrees Celsius, oxygen penetration at high stresses to the crack tip, and the combination with separated atoms at the grain boundaries, such as Ti and Nb, leading to the formation of a brittle oxide layer along the grain boundaries, contributed to intergranular brittle fracture in the sample
  9. Keywords:
  10. MP210 Superalloy ; Fracture Mechanism ; Stress Assisted Grain Boundary Oxidation (SAGBO) ; Hot Fracture ; High Temperature Fracture

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