Low cycle fatigue behavior of Inconel 706 at 650 °C

Effect of microstructure on low cycle fatigue behavior of Inconel 706 at 650°C

“…The authors made similar observation on IN706 specimens with the size of grain ranging from 60 to 80 μm. 16 Unlike those with fine grain structure, an initiation of crack may be dominant at PSBs for those specimens with relatively large grain size over 100 μm. 50 The FCP resistance of IN706 and resultant N P may also be influenced by grain size.…”

“…As previously reported, elevated temperature LCF behavior of IN706 was similar to that of IN718 counterpart. 16 It was noted that the Coffin-Manson relationship of IN706 varied with different forged discs (F1 specimens vs F2 specimens) and the location (center vs periphery). The overall resistance to LCF at 650 C was greater for the F1 specimens than the F2 specimens, and those prepared from the periphery tended to have higher resistance to LCF than those from the center.…”

“…The carbides in IN718 can serve as sites for crack initiation under cyclic loading, depending on the size of grain. 16,21 A crack can, for example, be initiated preferentially at carbides for those specimens with grain size smaller than the average size of carbides. The authors made similar observation on IN706 specimens with the size of grain ranging from 60 to 80 μm.…”

“…It was also found that the crack initiation behavior of IN706 was influenced by the presence of carbides, and the mode of crack propagation was either transgranular or intergranular. 16 The microstructure of Ni-based superalloy in general consists of major strengthening phases of γ 0 (Ni 3 Al), γ 00 (Ni 3 Nb), needle-like particles of stable δ (Ni 3 Nb) orthorhombic phase, Acicular η (Ni 3 Ti) phase, and light gray blocks of TiC and NbC carbides. 17,18 Brittle Laves intermetallic compound has MgZn 2 lattice type with a structure of HCP (hexagonally close packed) and can be formed in IN718 as a result of segregation.…”

“…Etching was conducted using an aqua regina solution (30-mL HCl + 10-mL NHO 3 + 20-mL H 2 O). 16,36,37 The grain size was measured by using a linear intercept method according to ASTM E112. Strain-controlled LCF tests were conducted according to ASTM E606 using a servo-hydraulic dynamic testing machine (model: Instron 8801) at 650 C. 38 Applied total strain amplitude was controlled to be 0.6%, 0.5%, 0.4%, and 0.3%, respectively, at an R ratio (minimum stress/ maximum stress) of À1 and a frequency of 0.25 Hz.…”