Laser Assisted Cold Spray Deposition

Abstract

This chapter will review the current state of the utilization of lasers to enhance the cold spray process both during and after deposition. While high and low-pressure cold spray has been successfully applied to a variety of metallic alloys, there is a need to increase deposition efficiency, permit the use of heavier and less expensive spray gases, and to tailor the microstructure of the sprayed material. Over the past decade, laser-assisted cold spray (LACS) has been introduced and developed to address these needs. In this process, the laser acts as a localized heat source softening the substrate and the deposited powder particles. This thermal softening in turn facilitates the deposition of hard materials and also enhances the deposition behaviour at lower powder particle velocities, allowing the use of less expensive processing gases like nitrogen. LACS has been applied in both co-axial and off-axis forms. The off-axis geometry has shown improvements in the deposition of titanium alloys, stellite, tungsten, and even oxide dispersion strengthened steel. While LACS can improve the deposition efficiency, it will also impact the microstructure of the sprayed material, either positively or negatively, depending upon the heat input used. Recent work has shown an increase in grain size and coarsening of precipitates during the LACS process. Understanding and controlling heat input during LACS are key to correctly producing the desired microstructure and mechanical properties of the deposited material. This chapter will introduce the LACS approach, present its applications to different alloy systems, discuss its advantages and disadvantages and offer some thoughts about its development in the near future.