Creep-Fatigue and Thermo-Mechanical Fatigue of Friction-Welded IN 718/MarM247 Dissimilar Joint

Abstract

The high temperature strength of the friction welded superalloy joint between cast polycrystalline Mar-M247 and the forged IN718 alloys has been investigated under low cycle and thermomechanical fatigue loadings, in comparison with those of the base materials. The experiments showed that the lives of the dissimilar joints were significantly influenced by the test conditions and loading modes. Not only the lives themselves but also the failure positions and mechanisms were sensitive to the loading mode. Especially under the loading conditions in which the creep-fatigue interaction was pronounced, some specific failure phenomena appeared in the DFW joint. The fracture behavior dependences on the loading modes and test conditions were discussed, based on analyses of the macroscopic elastic follow-up mechanism, the stress state by finite element method, and the inhomogeneous microstructure in the joint.

Effect of the Welded Zone Property on Behavior of a Dissimilar Superalloys Friction Joint under Creep Loading at Elevated Temperature - A Simulation Approach

“…The joint fails adjacent to the interface on the IN718 side. It should be noted that under the same creep loading, the strength of the base alloy IN718 is lower than that of MM247 [14].…”

“…The procedure of welding fabrication for the dissimilar joint (denoted DJ) between forged Inconel 718 (denoted IN718) and cast Mar-M247 (denoted MM247) was presented in previous works [7,14]. The experimental measurements of the joint properties were also thoroughly presented in [7].…”

“…Wrought superalloys can be welded to cast superalloys using friction welding. Such joints possess superior strength [7,14]. However, the microstructure was significantly recrystallized by the thermal and mechanical deformations induced by the welding process.…”

“…However, the microstructure was significantly recrystallized by the thermal and mechanical deformations induced by the welding process. In the joint between the forged Inconel 718 and the cast Mar-M247, a representative recrystallized microstructure adjacent to the interface on the Inconel 718 side was formed with a few hundred µm [7,14]. Moreover, such a welded microstructure is believed to possess a different creep resistance than that of the base Inconel 718 [15,16].…”