Metal injection molding of W-Ni-Fe microcutters

This investigation applies metal injection molding (MIM) to fabricate precise microcutters from W-Ni-Fe alloy powder. The hard and brittle W-Ni-Fe alloy is difficult to machine, and MIM must be applied to produce near net-shaped products. MIM involves the injection molding of feedstock by blending metal powder and binders, debinding, and sintering. Liquid-phase sintering is commonly adopted to improve the density and mechanical properties of the sintered parts, but it is inferior in terms of dimensional stability. This study elucidates the dimensional stability of sintered parts made from W-Ni-Fe alloy feedstocks that contain 83 and 93 wt% W. The powder injection molding of microcutters that demand micrometer-scale precision is considered as an example. The Taguchi method is utilized to optimize injection molding and sintering parameters, effectively optimizing the dimensional stability and mechanical properties. Experimental results show that (1) feedstock with 93 wt% W exhibited little and consistent shrinkage (25%-26%); (2) the optimal injection molding parameters determined by the Taguchi method yield an eccentricity of over 18 %, and (3) in the sintering process, low heating rate significantly improves dimensional stability. The average hardness of microcutters, sintered at various heating rates, ranges from Vickers hardness 446 to 452.