Novel Cast Ni‐Based Superalloys with Superb Weldability and Mechanical Properties Screened by a Multiperformance‐Oriented Criterion

Abstract

Herein, innovative cast Ni‐based superalloys that not only withstand temperatures up to 800 °C but also offer superior weldability, robust tensile strength at both room and elevated temperatures, and a reduced density are introduced. The new Ni‐based superalloys are optimized via calculation of phase diagrams‐based high‐throughput thermal calculation and program‐controlled composition screening. A new multiperformance‐oriented criterion is devised, encompassing quantitative weldability indices, volume fraction of γ′, electron vacancy number, density, solidus temperature, and freezing range to optimize the alloy composition. Weldability indices, rooted in the solidification crack initiation mechanisms, prove equally applicable to both current interested alloys and commercial superalloys. The crack length of the optimized alloy after the constrained welding test is only 3.08% of the total weld length. It is unveiled that solidification cracking (SC) emerges as the pivotal factor governing the weldability of these alloys. The mechanism of SC for such superalloys is originated from the addition of Nb, Ti, Mo, and W, which results in the microsegregation of the composition and the precipitation of (Nb, Ti)‐rich constituents or M(Ta, Nb, Ti)C carbides in the liquid film of the central interdendritic region. This work hopefully helps to find promising candidates for the combustion chamber of aeroengines and other high‐temperature casts.