Effect of hyperbranched polyester binders on properties of Fe–Fe3P bonding mixed powders

Fe–Fe3P adhesive premixed powders were prepared by using hyperbranched polyester as the binders. The microstructure of the powders was observed by scanning electron microscope. The effect of hyperbranched polyester binder content (mass fraction) on the properties of the Fe−Fe3P powder mixture and the sintered products was studied. The results show that the proportion of small particle size powders with particle size ≤10 μm (mostly Fe3P powders) in the bonded mixed powders accounts for 0.65% of the total number of powder particles, which is significantly lower than that of the un-bonded mixed powders (5.93%). Hyperbranched polyester can successfully bond the Fe3P powders to the iron powder surface, which is beneficial to improve the uniformity of phosphorus in the mixed powders and prevent segregation. The Fe–Fe3P bonded mixed powders with 0.10% terminal hydroxyl hyperbranched polyester show the best powder fluidity and loose packing density. The pressing pressure of the Fe–Fe3P green billets with the same density increases with the increase of the mass fraction of hyperbranched polyester. The addition of hyperbranched polyester binder can reduce the size change rate of the sintered body before and after sintering, improve the transverse fracture strength of the sintered body, and maintain good bonding property in the actual production process.