Inconel 718 is a nickel-based superalloy that is often used in aircraft and engine applications due to its high tensile strength, corrosion resistance and light weight. It is also a popular choice for downhole tooling, valves and flanges in the oil and gas industry.
Mechanical Properties: in718 possesses high tensile and yield strengths, which are a good indicator of its strength. It can withstand high temperature and pressures and is very resistant to erosion, oxidation, and corrosion in extreme environments.
A variety of surface enhancement techniques are currently being used to improve the mechanical properties and performance of a wide range of metals, including AM in718. However, AM materials have limited fatigue lifespan when subjected to elevated temperature environments. The main limiting factors in the AM material’s fatigue lifespan are the microstructure and grain size.
In addition, the presence of interdendritic d phase degrades the ductility and fatigue behavior at higher temperatures. It is believed that controlling the d phase by using different heat treatments can enhance the long-term thermal stability of AM Inconel 718 alloy.
Microstructure: in718 has a relatively large grain size and is typically characterized by a coarse-grained microstructure with low porosity, which contributes to its high strength and ductility. The microstructure can be altered by various heat treatment processes, such as solution annealing, aging and precipitation hardening.
During these heat treatment processes, the niobium content in in718 increases and the d phase and Laves phase can form, which is known to deteriorate the U’’ phase strengthening ability of in718. Therefore, it is necessary to control the d phase and Laves phase during aging and precipitation hardening in order to optimize the AM in718 material.