Microstructure and Mechanical Properties of Cold-Sprayed Ni/CrC-NiCr Composites with Varying Binder Phases

Abstract

This study investigates metal matrix composites fabricated by cold spraying nickel (Ni) as the matrix with two different chromium carbide/nickel chrome (CrC/NiCr) cermet powder formulations as the reinforcement onto A514 steel. The research focuses on understanding the effects of the metallic binder (NiCr) ratio in the cermet particles and the matrix-to-cermet (i.e., Ni-to-CrC/NiCr) ratio in the feedstock blend on the microstructure and mechanical properties of the resulting composites. The microstructure of the as-received powders and the cold-sprayed deposits was analyzed using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) techniques, while the mechanical performance of the deposits was evaluated using microhardness, tensile, and triple-lug shear tests. Results indicate that increasing the binder percentage in the cermet particles enhances deposition efficiency, leading to a higher area fraction of the retained cermet in the final deposit, improved interparticle adhesion, reduced porosity, and superior ductility and shear strength. The study also identifies three distinct crack propagation patterns that explain the variations in fracture behavior among different MMCs and metallic deposits. These patterns are governed by the extent of cracking in the cermet particles and the interparticle bonding strength, which in turn affect the ultimate tensile strength (UTS) of the coatings.