Comparative investigation of microstructure and properties of Ni-coated FeSiAl soft magnetic composite coatings produced by cold spraying and HVOF

In this work, the techniques of cold spray (CS) and high velocity oxygen-fuel (HVOF) were employed to fabricate Ni/FeSiAl soft magnetic composite (SMC) coatings by using Ni-coated FeSiAl composite powder. The micro-structural features were characterized in terms of scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses. The tribological and magnetic properties of the Ni/FeSiAl SMC coatings were also comparatively studied. Results showed that the CS coating exhibited higher particle deformation and much higher density, whereas the HVOF coating showed more visible defects and slightly higher oxide content. Both CS coating and HVOF coating resulted some loss of FeSiAl particles during deposition, while a higher content of FeSiAl particles was achieved in the HVOF composite coating, indicated a higher deposition efficiency of FeSiAl particles during HVOF deposition. According to the XRD analysis, both SMC coatings had no obvious oxidation and phase transformation during deposition processes. The EDS analysis proved partially melted particles during HVOF deposition. Tribological tests revealed a better wear performance of the CS coating as a result of the enhanced plastic deformation and microhardness. The HVOF coating showed a better magnetic performance, with a lower coercivity and a higher saturation magnetization compared to those of CS coating. This can be explained by a higher retainability of FeSiAl particles and a smaller strain stress generation during HVOF deposition.