Abstract
<jats:p>This paper is devoted to the scientific and technological foundations for improving the structure and performance characteristics of Co–Cr–W-based coatings produced by plasma spraying through laser remelting. The main objective of the study is to evaluate the possibilities of densifying plasma-sprayed coatings—initially characterized by high porosity and heterogeneous microstructure—via laser treatment, optimizing their microstructure, and enhancing their mechanical properties, particularly impact toughness. For this purpose, the optimal coating thickness was theoretically and experimentally justified, the influence of laser processing parameters on porosity was analyzed using statistical methods, and the effect of Ca and Zr microalloying on the structural and mechanical properties was systematically investigated. Plasma-sprayed Co–Cr–W-based coatings were subjected to laser remelting, and the main technological parameters influencing the effectiveness of this process were identified. The effect of laser beam travel speed (0.83×10⁻³–5×10⁻³ m/s) and beam diameter (1–5 mm) on porosity was quantitatively evaluated using the Design of Experiments (DOE) methodology. Based on the experimental results, a regression model was developed, and analysis of variance (ANOVA) was performed. Statistical analysis showed that the most significant parameter affecting porosity is the laser beam speed (p < 0.01), confirming that heat input and melting–solidification kinetics play a decisive role in coating structure formation. The effect of beam diameter was also observed, though it was found to be less influential than beam speed. Theoretical calculations and experimental validation determined that the optimal coating thickness for repair and reinforcement applications is 0.7 ± 0.05 mm. Within this range, the coating ensures strong metallurgical bonding with the substrate while minimizing the risk of crack formation and internal stresses during laser processing. Laser remelting significantly reduced the initial high porosity level (36–40%) to 1–3%, indicating substantial densification and enhanced mechanical strength of the coating. Additionally, the influence of Ca and Zr microalloying on microstructure formation and mechanical properties was investigated. These elements were found to refine the grain structure, homogenize the microstructure, and evenly distribute phases. Consequently, the impact toughness of the coatings increased 2.0–2.5 times compared to the initial state, indicating improved resistance to dynamic loading and enhanced operational reliability. The results demonstrate that laser remelting of plasma-sprayed Co–Cr–W-based coatings is an effective technological approach for comprehensive improvement of structural and mechanical properties. The proposed method ensures minimal porosity, microstructure homogenization, and enhanced mechanical performance, highlighting its potential for repairing and reinforcing machine parts subjected to wear, impact, and high mechanical loads. Keywords: laser remelting, plasma spraying, Co–Cr–W alloy, porosity, impact toughness, microalloying, DOE optimization, restoration, mechanical, strengthening, beam diameter.</jats:p>