Interior long‐life‐fatigue cracking behavior and life prediction of a selective laser melted GH4169 superalloy at different temperatures and stress ratios

Abstract

The axial fatigue tests at elevated (650 C) temperature with stress ratios of 0.1 and À1 were conducted under the loading cycle range of 10 4 -10 8 cycles to investigate interior cracking mechanism at elevated temperature of one selective laser melted GH4169 superalloy. Results showed that the interior fatigue crack nucleation was the main failure mode with both stress ratios at 650 C in the long-life regime. The interior crack nucleation region consisting of many facets was formed under shear stress and strain according to the 3D morphology restructure of the fracture surface. Combined with the evaluation of the threshold stress intensity factor, the transition lengths from a small crack to a long crack for interior failure at both stress ratios were evaluated. Based on the above analysis, the microstructure-related interior failure mechanism was summarized. Finally, crack nucleation and propagation lives were predicted to obtain the total fatigue life, which showed that the prediction and experimental data scattered between the factor-of-three boundaries.

Effect of texture evolution and defect on the crack initiation of a Ni‐based superalloy electron beam welded joint

“…16 In recent years, additive manufacturing is a new method to produce GH4169 or Inconel 718. 17 In fact, welding is similar to AM processing, and the resulted microstructure can be compared each other. 18 In the selective electron beam melting of Inconel 718, the adjustment of scanning strategy can change the direction of the thermal gradient during solidification to obtain grains with different morphologies; therefore, the mechanical properties can be improved.…”

“…Micro‐segregation of Nb and Laves phases in 718 EBW joints can be reduced by applying suitable electron beam oscillation techniques 16 . In recent years, additive manufacturing is a new method to produce GH4169 or Inconel 718 17 . In fact, welding is similar to AM processing, and the resulted microstructure can be compared each other 18 .…”

Guest editorial of virtual special issue: The eighth international conference on very high cycle fatigue (VHCF8), held online from July 5 to 9, 2021, and distributed from Sapporo, Japan

“…Sun et al 3 investigated the interior cracking behavior and the life prediction of GH4169 superalloy in the VHCF regime. The experimental results showed that interior fatigue crack nucleation was the main failure mode regardless of the stress ratio.…”