Laser Assisted Cold Spray Deposition of Inconel 718 and Inconel 625

In the present work, we apply in situ laser heating to enhance the high pressure cold spray (HPCS) deposition of IN625 and IN718. These alloys are important nickel-based superalloys, widely used in a variety of propulsion components on aircraft. High pressure cold spray deposition of these superalloys is still challenging and success in the reported literature has been limited. The use of in situ laser heating during HPCS, or laser assisted cold spray (LACS), has been demonstrated to be a promising method for improving the deposition for challenging materials such as high strength steel, titanium, and Stellite. In this work, LACS was accomplished using a customized system with a 4 kW diode laser in combination with a high pressure cold spray system. Commercial as-atomized IN718 and IN625 powders were cold sprayed using helium gas at a set of optimized HPCS conditions. The LACS system has an in-line optical pyrometer, and laser heating was provided using a set temperature (700-900˚C) under closed-loop feedback between the pyrometer and the laser power. The deposits produced by LACS were highly dense in their as-sprayed condition (porosity< 1%). High laser surface temperatures (800 and 900˚C) dissolved the intermetallic networks present in the feedstock powder. Recrystallization and grain growth were also observed at high laser surface temperatures for both IN718 and IN625 deposits. The microhardness of the deposits decreased with increasing the laser surface temperature and the correlation between the evolved micro- and nanostructures and the hardness/strength will be discussed.