Enhancement of mechanical properties of LDEDed IN738LC alloy by solid-solution strengthening coupled with precipitation-strengthening

Abstract

The high cracking susceptibility is the major obstacle to the wide application of high γ′-phase nickel-based superalloys in additive manufacturing. It is especially important to explore the effects of alloying elements during the nickel-based superalloys and establish a new alloy design criterion. In this work, a new nickel-based superalloys with crack-free and low porosity was fabricated by adjusting the content of solid-solution and precipitating elements of Inconel 738LC (IN738LC) alloy utilizing laser directed energy deposition (LDED) technology, achieving an increase in strength and ductility simultaneously. The newly developed nickel-based superalloys maintain a high content of γ′-phase and display substantial fine bulk MC carbides, resulting in higher strength (UTS: 1461 MPa, YS: 1105 MPa) and elongation (EL: 12.9%). After heat treatment, extensive long-stripes of M23C6 carbides were detected in the IN738LC sample, which led to poor tensile properties at high temperature (900 °C). However, due to the finer γ′ phase uniformly distributed in the matrix, the developed new nickel-based superalloys exhibits optimal tensile properties (UTS: 593 MPa, YS: 475 MPa) and ductility (9.4%) at 900 °C. This approach can provide guidance for the design of high γ′-phase nickel-based superalloys for additive manufacturing starting from elemental powders.