Cold Spraying of Mechnically Alloyed Compositionally Complex Co18Cr24Fe14Ni33V11 Alloy: Processability, Microstructure, Mechanical Properties, and Residual Stress Evaluation

The growing demand for materials capable of withstanding demanding environments has driven interest in compositionally complex alloys (CCAs). Concurrently, cold spray (CS), a solid-state technique that preserves the feedstock microstructure, has emerged as a promising method for depositing CCAs. This work represents the first systematic evaluation of cold spray processability of a novel mechanically alloyed (MA) Co 18 Cr 24 Fe 14 Ni 33 V 11 CCA powder, developed within the EU Horizon 2020 FORGE project and designed to achive high hardness. The CS process parameters, including gas temperature, pressure, and nozzle pre-chamber configuration, were systematically studied to achieve an optimal combination of deposition efficiency (DE), thickness per pass, and coating density onto various steel substrates (S700MC, H13, and AISI 310). The results demonstrated that a gas temperature of 1100 °C and a pressure of 40 bar, combined with a short pre-chamber, minimised porosity (<0.3%), achieved DE above 30%, and produced coating thicknesses exceeding 40 μm per pass. Correlation analyses identified temperature as the primary driver of coating quality, with pressure playing a secondary role. The microstructural analysis confirmed the effective transfer of powder microstructure to coating, which exhibited an median microhardness of 729 ± 63 HV 0.1 . This high hardness is attributed to the alloy composition, work hardening during mechanical alloying, and severe plastic deformation during deposition – placing it among the hardest cold sprayed CCA coatings reported in the open literature. Adhesion strength inversely correlated with substrate hardness, peaking at > 64 ± 1 MPa on the softer AISI 310 substrates. Neutron diffraction measurements enabled evaluation of through-thickness residual stresses in the coating-substrate system, revealing a predominantly compressive stress state (–142 ± 27 MPa) within the coating. Interpretation using the analytical model for progressively deposited coatings indicates that the measured stresses arise from the combined effects of deposition-induced peening and thermal misfit between the coating and substrate.