Advances in Triple Melting Superalloys 718, 706, and 720

Abstract

Triple melting (TM) by VIM+ESR+VAR has been highly successful for Alloy 718, large diameter ingots of Alloy 706, and high hardener alloys such as Alloy 720. Frequencies of ultrasonic indications for TM 718 are significantly lower than for VIM+VAR melt 718 because fewer clusters of inclusions are present, The cleanliness associated with TM 718 was verified by microscopy and by electron beam melting of buttons after VIM, VIM+ESR, and TM. Furthermore, white spot frequencies were found to be reduced for TM 718. Ultrasonic defect frequencies of Alloy 706 and Alloy 720 are also low. A major advantage of triple melting Alloy 706 is that ingots up to 36 inches (914mm) in diameter can be melted without freckles or positive segregation problems.

A Study of Microstructural Tensile and Fatigue Properties Coupled with Digital Image Correlation of Hybrid Manufactured Inconel 718 Parts by Extrusion and Powder Bed Fusion

“…Vacuum induction melting plus electroslag remelting results in a rougher dendritic microstructure with more sever macrosegregations and much larger microstructural constituents such as NbC. [ 43 ] While metal forming at high temperature and the heat treatment processes that follow break down dendritic microstructure and dissolve Laves phase, phases with high stability such as NbC and (Ti,Nb)(N,C) often persist. Furthermore, due to their brittleness, these phases are known to fracture and disintegrate if plastic strains during processing are high, as is the case for extrusion processes.…”

Characterisation of secondary phases in Ni-base superalloy Rene 65

“…This aim is achieved by the forming of more stable γ ′ precipitates than γ ”, which occur in the currently used alloys like Inconel 718 and are prone to dissolve at higher temperatures [2,3]. In contrast to the powder metallurgical alloys like IN100, Rene 65 is produced by the less cost-intensive triple melting technology which consists of Vacuum Induction Melting (VIM), followed by Electroslag Remelting (ESR) and Vacuum Arc Remelting (VAR) [4]. The Rene 65 is a fine-grained and γ ′-strengthened alloy which is processed by the cast and wrought route.…”

Clean Metal Spray Forming

“…For this study, the electron beam button test [26] was used to evaluate the cleanliness. Five 38mm x 38mm x 162mm (1.5" x 1.5" x 6.375") blanks from the top half of the as-sprayed preform were machined into EB electrodes.…”