Microinjection moulding of 316L/17-4PH and 316L/Fe powders for fabrication of magnetic–nonmagnetic bimetals

In the investigations presented here, the feasibility of producing magnetic–nonmagnetic bimetals made of 316L/17-4PH and 316L/Fe powders by micro-metal injection moulding process (μ-MIM) was studied. In order to achieve sound replication of small specimens with dimensions less than 1 mm, very fine powders with mean particle sizes in the range of 3–7 μm were used. A wax–polymer binder system specially designed for micro-moulding was used to make up the feedstock. The isothermal and non-isothermal sintering behaviour of the moulded components was evaluated under hydrogen atmosphere. The effect of powder-binder-ratio of the feedstock, master alloy addition, and sintering conditions on the co-sintering compatibility between the components was investigated. In this study, 316L and 17-4PH showed the best co-sintering compatibility and sound joining of the materials was achieved. When combining 316L and iron, using a 316L master alloy (MA) mixed from NiCrMo and iron powder reduced the mismatch incompatibility with plain iron from 12.7% to 1.6%. So the 316L/17-4PH and 316L MA/Fe were found to be suitable for micro-co-injection moulding. The systems can be used for fabrication of small magnetic–nonmagnetic bimetals with contact areas less than 1 mm2.