Effect of metal particle size and powder volume fraction on the filling performance of powder injection moulded parts with a microtextured surface

Metal injection moulding of miniaturized devices demands unique feedstock materials and mould designs with high dimensional accuracy. In this work, the influences of the powder size and powder content of 17-4 PH stainless steel feedstock and the influence of mould design on the successful production of micro-scaled structures were investigated. Ni mould inserts with high dimensional accuracy and texture sizes of 50-200 mu m using a new microtexturing technique were manufactured. 17-4 PH stainless steel feedstocks with powder sizes (D90) of 10 and 22 mu m and powder contents of 60 and 65 vol.-% were compounded. The rheological properties of the obtained feedstocks were characterized with a capillary rheometer to assess their flowability. The results showed that 10 mu m sized particles caused a slight but not significant increase in the viscosity. The highest viscosity increase occurred when the powder content increased from 60 to 65 vol.-%. Feedstocks with the 10 mu m powder particles ensured complete filling within microtextures for all mould variations. However, when using feedstocks with 22 mu m particles, the filling capabilities of the 50 and 100 mu m microtextures decreased with increasing powder content. The shape retention was better for those micropillars produced with mould inserts with 200 mu m cavities than for the micropillars replicated with the inserts having cavities of 50 and 100 mu m. The results indicated that the proposed mould insert preparation technique opens new possibilities for mass production using the mu MIM process to create micro-scaled components using feedstocks without nanoparticles.

Automated summary

The study investigated the influences of powder size, powder content, and mould design on the successful production of micro-scaled structures using 17-4 PH stainless steel feedstock. It was found that 10 μm sized particles ensured complete filling within microtextures for all mould variations. The results suggest that the proposed mould insert preparation technique opens new possibilities for mass production of micro-scaled components using feedstocks without nanoparticles.