Grain Boundary Serration in Nickel-Based Superalloy Inconel 600: Generation and Effects on Mechanical Behavior

Abstract

Grain boundary serration in the superalloy Inconel 600 was studied. Two microstructural variants, one with nonserrated and the other with serrated grain boundaries were generated by altering the heat-treatment conditions, while keeping other aspects of the microstructure unchanged. The effect on the creep response between 700°C and 900°C was measured, and the different failure modes and accumulated damage were quantified using high-angular resolution electron backscatter diffraction analysis in the scanning electron microscope and also by X-ray computed tomography. It is found that serration plays a more crucial role in the high-temperature/low-stress regime when an intergranular cracking mechanism involving cavitation is operative; here it plays a role in improving both creep life and creep ductility. Any effect of serration is less prevalent at low temperatures where transgranular failure is dominant.

Precipitation Kinetics and Morphology of Grain Boundary Carbides in Ni-Base Superalloy Haynes 282

“…[12] Formation of serrated boundaries during slow cooling and a resulting beneficial effect on the creep behavior have been reported for several Ni-base superalloys. [13][14][15][16] The present results shows that grain boundary serrations can also form during low-temperature annealing. At much higher aging temperatures, > 1100°C, the carbides completely dissolve and the grain boundaries are free from carbides.…”

Quantitative Precipitate Classification and Grain Boundary Property Control in Co/Ni-Base Superalloys

“…[1][2][3][4] A secondary effect of grain boundary precipitate interactions is the ability to facilitate grain boundary serration mechanisms, also an essential consideration in modern superalloy grain boundary engineering. [5,6] This work develops the V208 series first presented by Knop et al [7][8][9] A set of Co/Ni-base superalloys based on V208C are presented, with Mo additions (for solid solution strength) and varied C, B, Zr, and Ti content for grain boundary chemistry adjustment. We additionally characterize the as-received coarse-grained RR1000 as well as cast and wrought V208C for comparison.…”

Advancing characterisation with statistics from correlative electron diffraction and X-ray spectroscopy, in the scanning electron microscope

“…Loading colour map is unnormalised between maps to show contrast 2 . No PC strongly contributes to the highlighted grain (1)(2)(3)(4)(5)(6), and the VARIMAX rotated component that most loads it (f) includes significant signal from several other precipitates and matrix. This results in the corresponding RC-EBSP being dominated by FCC Co signal, and indexing accordingly (point C in Figure 7).…”

“…In the present work, we develop a new approach using an example in Co/Ni-base superalloys. In these alloys, there are carbide precipitates that are known to strongly influence fatigue and tertiary creep performance [5][6][7][8][9]. The precipitates are thought to increase boundary cohesivity and to mitigate sliding.…”