A Critical Review of the Material Characteristics of Additive Manufactured IN718 for High-Temperature Application

Abstract

This paper reviews state of the art additive manufactured (AM) IN718 alloy intended for high-temperature applications. AM processes have been around for decades and have gained traction in the past five years due to the huge economic benefit this brings to manufacturers. It is crucial for the scientific community to look into AM IN718 applicability in order to see a step-change in production. Microstructural studies reveal that the grain structure plays a significant role in determining the fatigue lifespan of the material. Controlling IN718 respective phases such as the ϒ’’, δ and Laves phase is seen to be crucial. Literature reviews have shown that the mechanical properties of AM IN718 were very close to its wrought counterpart when treated appropriately. Higher homogenization temperature and longer ageing were recommended to dissolve the damaging phases. Various surface enhancement techniques were examined to find out their compatibility to AM IN718 alloy that is intended for high-temperature application. Laser shock peening (LSP) technology stands out due to the ability to impart low cold work which helps in containing the beneficial compressive residual stress it brings in a high-temperature fatigue environment.