Multiscale Simulation of Shot-Peening-Assisted Low-Pressure Cold Spraying Based on Al-Zn-Al2O3 Coatings

Abstract

Low-pressure cold spraying has gained much significance for its good economy in recent years. However, compared with high-pressure cold spraying, the unsatisfactory performance of coatings prepared by this method is a key problem restricting its further development. To improve the properties of the coating without incorporating severe conditions, the paper proposed an original shot-peening-assisted low-pressure cold-spraying method (i.e., SP-LPCS). By proceeding with cold spraying and shot peening alternately, SP-LPCS was proved to enhance the mechanical property of the coating effectively. Mixed particles of Zn, Al, and Al2O3 were adopted as the coating powder. Effects of shot-peening pressure, flow rate, and shot size on the micromorphology and the microhardness variance were studied. Results shows that the thickness of the plastic deformation layer stabilizes as the impact time increases to 6. The microscopic simulation of the deformation shows that according to the different metal characteristics of the powder, brittle grains fracture while plastic grains go through deformation and refinement. Meanwhile, the porosity decreases greatly after the impacts, resulting in a higher denseness of the coating. Several factors mutually contribute to the performance improvement of the coating. The microhardness of the material was increased after SP-LPCS, and obvious strengthening belts were observed, with the highest microhardness being 90.93Hv.

Cold Spray Coatings of Complex Concentrated Alloys: Critical Assessment of Milestones, Challenges, and Opportunities

“…The high-impact velocity of the impinging particles contributes to the peening effects [30]. The mechanism is likened to shot peening for increased fatigue strength in most structural components [38][39][40][41][42][43][44]. The quenching stresses are attributed to the compaction of impacted particles often impeded or restricted by the underlying coatings or substrate materials.…”

“…Three main types of models are used to simulate the cold spray processes. These include the finite element-based models, constitutive equations, and models for describing the bonding at the particle-substrate and particle-particle interfaces [39,58]. A summary of the models and their applications to cold spray processes are highlighted.…”