Study of nickel-based super-alloys Inconel 718 and Inconel 625 in high-deposition-rate laser metal deposition.

Highlights • Formed by HDR-LMD, IN625 seem have finer microstructure than that of IN718. • With approx. 2 kg/h deposition rate, IN625 is nearly whole density, IN718 porous. • There exists stronger convection in the melt pool of IN625 than in IN718. • The convection may cause faster heat transfer so that accelerates the solidification. • The convection may promote the escape of the gas that trapped in the process. Abstract Nickel-based super-alloys Inconel 718 (IN718) and Inconel 625 (IN625) have comparable chemical composition and similar physical constants such as density and melting range; however, in high-deposition-rate laser metal deposition (HDR-LMD), processes with IN625 are not transferable to that with IN718. In order to compare HDR-LMD process with IN718 and IN625, the current study has been conducted. Initially, parallel experiments have been performed, and the metallurgical analysis for macro- and microstructures have been carried out. Then, the strengthening effects of HDR-LMD for both alloys have been compared. Finally, in order to understand and explain the obtained results, both processes have been characterized by using a high-speed camera. According to the study, the following conclusions have been drawn: in comparison to IN718, there seems to have a stronger convection in the melt pool of IN625; this convection could be the reason for the faster solidification of IN625 since it may accelerate the dissipation of heat; As a further consequence of the stronger convection, the degassing during the solidification can be enhanced. [ABSTRACT FROM AUTHOR]