Oxide Formation In Metal Injection Molding Of 316L Stainless Steel

Abstract

The effects of sintering condition and powder size on the microstructure of MIMed parts were investigated using water-atomized 316L stainless steel powder. The 316L stainless steel feedstock was injected into micro mold with micro features of various shapes and dimensions. The green parts were debound and pre-sintered at 800• C in hydrogen atmosphere and then sintered at 1300• C and 1350• C in argon atmosphere of 5torr and 760torr, respectively. The oxide particles were formed and distributed homogeneously inside the sample except for the outermost region regardless of sintering condition and powder size. The width of layer without oxide particles are increased with decrease of sintering atmosphere pressure and powder size. The fine oxides act as the obstacle on grain growth and the high sintering temperature causes severe grain growth in micro features due to larger amount of heat gain than that in macro ones.

Archives of Metallurgy and Materials

“…The results show that the average shrinkage ratio and the dimensional accuracy are almost constant. The densities of sintered samples were measured to be 7.39 ± 0.015 g/cm 3 . it is of interest that the sintered densities of all samples are almost constant, although the green density is noticeably different as shown in Fig.…”

“…Powder injection molding (PiM) process combines the traditional shape-making capability of plastic injection molding with the material flexibility of powder metallurgy. The process, in general, follows four steps: (1) feedstock preparation by mixing metal powders with organic binders, (2) injection molding to shape components, (3) debinding process to remove the organic binders, and (4) sintering process to consolidate the debounded components in the desired dimensional properties and density [1][2][3][4][5][6].…”