Abstract
In this study, the influence of cold rotary swaging on microstructure and mechanical properties of the precipitation-strengthened nickel-based superalloy 718 (Alloy 718) was investigated. The initial stages of work-hardening were characterized by means of microhardness, electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) analyses. Furthermore, attention was devoted to the mechanical behavior at ambient and elevated temperature (550 °C) in uniaxial tension and compression. Rotary swaging to different true strains of maximum varphi = 0.91 caused a moderate increase of microhardness and enhanced markedly the load-bearing capacity in tension, giving rise to yield strength beyond 2000 MPa. The mechanical strength R_{p0.2} in tension subsequent to rotary swaging perfectly correlates with increasing dislocation density rho estimated from XRD in the form of a Taylor-like relationship R_{p0.2} propto sqrt{rho }. In compression, transient stress–strain evolution without the occurrence of a clear elastic range and distinct yield phenomenon was observed. Restoration of the elastic range, accompanied by a pronounced increase of microhardness, was obtained by a post-swaging tempering treatment at 600 °C.
Highlights
DUE to its outstanding combination of mechanical properties, creep and corrosion resistance, the Nickel-based superalloy 718 (Alloy 718), often referred to as ‘‘Inconel 718’’ or ‘‘IN718,’’ has been applied vastly in demanding aerospace, power plant, and petrochemical applications.[1,2,3,4,5,6,7,8]. It is commonly utilized as wrought material in precipitation-hardened condition, where it is strengthened mainly by the D022-ordered metastable c00-phase (Ni3Nb). This phase appears as dispersed ellipsoidal discs of approximately 20 to 40 nm in diameter and 5 nm in thickness embedded in the cubic face-centered c-matrix
Large amount of deformation (u4 1⁄4 0:91) causes regions with very large misorientations (‡ 10 deg) close to grain boundaries of the initial microstructure. This is indicative of localized deformation to accommodate the different numbers of active slip systems, for example, eight and six in grains with h111i and h001i directions parallel to the rod axis, respectively
– Rotary swaging of Alloy 718 up to deformation degrees of u 1⁄4 0:91 caused an increase in microhardness from approx
Summary
DUE to its outstanding combination of mechanical properties, creep and corrosion resistance, the Nickel-based superalloy 718 (Alloy 718), often referred to as ‘‘Inconel 718’’ or ‘‘IN718,’’ has been applied vastly in demanding aerospace, power plant, and petrochemical applications.[1,2,3,4,5,6,7,8] It is commonly utilized as wrought material in precipitation-hardened condition, where it is strengthened mainly by the D022-ordered metastable c00-phase (Ni3Nb) This phase appears as dispersed ellipsoidal discs of approximately 20 to 40 nm in diameter and 5 nm in thickness embedded in the cubic face-centered c-matrix.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
