Preparation and characterisation of thermal sprayed neodymium iron boron magnetic coatings

Neodymium iron boron (Nd-Fe-B) is a type of rare-earth transition-metal hard magnet that is one of the strongest hard magnetic materials in the industry; and a very popular magnetic material in a variety of applications, from electronic devices to aerospace industries. Magnetic Nd-Fe-B films or coatings have been conventionally deposited using physical deposition methods, which is time and cost consuming and cannot produce films of thicknesses beyond 10 μm. In this work, thermal spray technology has been used as a cost-efficient alternative to the conventional techniques used to deposit Nd-Fe-B coatings. The coatings were deposited via flame spray and plasma spray techniques. The coatings deposited via flame spray technique were unable to build up beyond 50 μm thick, although the splat analysis showed reasonably well molten splats. The plasma spray process, on the other hand, was able to deposit coatings with thickness of ~200 μm. The microstructural features of the coatings, including the porosity and phase content, were analysed in detail to optimise the coating microstructure for magnetic and mechanical performance.