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<p>This study examines the initial cast microstructure of the M647 nickel-based superalloy following casting and homogenization, with a particular focus on the formation of deformation bands induced by mechanical loading. The new nickel-based superalloy M647 was cast by double vacuum process vacuum induction melting (VIM) + vacuum arc remelting (VAR) and then were homogenized at 1100, 1130 and1160 °C for 5 and 10 h. To study the structure, optical microscope (OM), scanning electron microscopy (SEM) images, elemental analysis based on energy dispersive spectroscopy (EDS), Vickers micro-hardness, and Vickers macro-hardness tests were used. Structural examinations showed that in the dendritic cast structure, niobium, molybdenum, and titanium elements segregated in the interdendritic regions, which included white islands rich in segregated elements and lamellar eutectics. Additionally, mechanical loading during surface preparation, in the form of manual force applied during coarse grinding for metallographic polishing, resulted in the formation of intersecting and parallel deformation bands consisting of both twinning and slip features. The morphology of the deformation bands around a Vickers indentations showed straight lines of twinning bands, indicating the dominance of the twinning mechanism over slip bands. An analysis of the deformation bands around hardness indentations in homogenized samples at various temperatures revealed that the amount of twinning bands is significantly higher in samples with the highest hardness. Our analyses indicate that the M647 superalloy exhibits a remarkably low stacking fault energy compared to conventional disk superalloys such as Rene65 and IN718.</p>

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An Investigation of the Initial Cast Structure and Deformation Bands in the Novel Nickel-Based Superalloy M647

  • 期刊论文

  • 发表日期：

    2025年11月29日

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  • Hamed Tahmasbi,
  • Maryam Morakabati,
  • Seyed Mehdi Abbasi

摘要

This study examines the initial cast microstructure of the M647 nickel-based superalloy following casting and homogenization, with a particular focus on the formation of deformation bands induced by mechanical loading. The new nickel-based superalloy M647 was cast by double vacuum process vacuum induction melting (VIM) + vacuum arc remelting (VAR) and then were homogenized at 1100, 1130 and1160 °C for 5 and 10 h. To study the structure, optical microscope (OM), scanning electron microscopy (SEM) images, elemental analysis based on energy dispersive spectroscopy (EDS), Vickers micro-hardness, and Vickers macro-hardness tests were used. Structural examinations showed that in the dendritic cast structure, niobium, molybdenum, and titanium elements segregated in the interdendritic regions, which included white islands rich in segregated elements and lamellar eutectics. Additionally, mechanical loading during surface preparation, in the form of manual force applied during coarse grinding for metallographic polishing, resulted in the formation of intersecting and parallel deformation bands consisting of both twinning and slip features. The morphology of the deformation bands around a Vickers indentations showed straight lines of twinning bands, indicating the dominance of the twinning mechanism over slip bands. An analysis of the deformation bands around hardness indentations in homogenized samples at various temperatures revealed that the amount of twinning bands is significantly higher in samples with the highest hardness. Our analyses indicate that the M647 superalloy exhibits a remarkably low stacking fault energy compared to conventional disk superalloys such as Rene65 and IN718.