Improved creep properties of Inconel 718 fabricated by selective laser melting from boron-phosphorus interaction

Abstract

The inferior creep ductility of Inconel 718 (IN718) fabricated by selective laser melting (SLM), which is unable to meet aerospace material specification (≥4%), limits its engineering application. Despite persistent optimization efforts in the SLM process and post-heat treatment, this issue remains unresolved. This study involved SLM fabrication of the modified IN718 with trace amounts of LaB₆ and/or P, followed by homogenization and double aging heat treatment. The addition of trace LaB₆ notably influenced the recrystallized grain structure and carbide precipitation at grain boundaries, while trace P addition had minimal impact. All samples exhibited similar γ′ and γ^″ strengthening precipitates. Creep tests conducted at 650°C/690 MPa revealed that the individual modification of LaB₆ showed limited improvement in creep performance and P showed no improvement, but the combined addition of LaB₆ and P led to a substantial enhancement in creep performance, especially reaching as high as 8.6% creep strain. This remarkable improvement in creep ductility is unlikely to arise from the altered grain structure and grain boundary precipitates induced by LaB₆ but predominantly arises from the synergistic effect of P and B in enhancing resistance to crack propagation during the third stage of creep.

GRAPHICAL ABSTRACT

KEYWORDS:

• Selective laser melting
• Inconel 718
• trace elements
• boron-phosphorus interaction
• creep performance

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the National Natural Science Foundation of China (grant number U22A20189).