Exploring the structural evolution of the NdFeB magnets with various carbon contamination in the PIM process

The Powder Injection Molding (PIM) process offers the possibility to obtain dense near-net shape NdFeB parts with magnetic properties similar to the conventional powder metallurgy counterparts. Understanding the structural evolution of the magnets with various carbon contamination coming from the organic binders will offer the possibility to improve the process. Here, the evolution of the structure of the NdFeB magnets with various carbon contamination within the PIM process was investigated. It was found that the carbon contaminates the Nd-rich phases forming a NdO x C y phase. For carbon concentrations higher than 5300 ppm wt., a tetragonal neodymium carbide phase was formed at the expense of the metallic Nd- dhcp phase. Moreover, 23 % of boron atoms are substituted in the main Nd 2 Fe 14 B magnetic phase, forming a Nd 2 Fe 14 B 0.77 C 0.23 phase.