Effect of Magnetic Field Type on the Flight State of Supersonic Plasma Spray Particles and Coating Properties

This paper aims to demonstrate the feasibility and effectiveness of using magnetic fields in the preparation of coatings. To achieve this, we have combined supersonic plasma spraying technology with a magnetic field to produce coatings that perform better. Specifically, we have prepared NiCrBSi-10%WC&Co coatings using supersonic plasma spraying under three conditions: no magnetic field, pulsed magnetic field, and constant magnetic field. In this study, we have compared and analyzed the droplet flight progression, coating morphology, coating micromorphology, and mechanical properties of the coatings under these three conditions. When both melted and unmelted particles spread over the matrix, broken edges appear. However, we found that the magnetic field can affect the magnitude and direction of the droplet velocity upon impact on the matrix. Additionally, the cross-sectional morphology of the coatings shows that the reinforcement aggregates due to the magnetic field’s promotion of internal flow during coating solidification. Further, our transmission electron microscopy analysis revealed that the magnetic field caused grain refinement. Moreover, we observed that the grain refinement effect was more significant under a constant magnetic field than under a pulsed magnetic field. Due to the growth of spreading morphology, enhanced phase aggregation, and fine-grain structure, the coatings produced in a magnetic field exhibited higher microhardness and adhesion properties. Overall, our results suggest that using magnetic fields in the preparation of coatings can significantly improve their performance.