Metal injection molding of sieve-size Ni-Mo steel powders

An investigation was carried out on the possibility whether metal injection molding using sieve size powders could be successfully applied to the fabrication of the high performance Ni-Mo-steel sintered parts. The powder-binder mixture composed of 45% low density polyethylene-15% carnauba wax-30% paraffin wax-10% stearic acid has shown a relatively good mixing property and moldability. An optimal amount of powder loading for injection molding was in the range from 61 to 63 vol.%, the critical value being 64 vol.% The binder mixture could be fully removed by wicking and thermal decomposition treatments followed by presintering treatment. The brown part made of sieve size Ni-Mo steel powders can be densified to the relative density above 97% by means of an enhanced sintering. The value of hardness and UTS of the MIM steel part sintered at 1230°C for 3 h was 44 HRc and 458±9 MPa, respectively. These mechanical properties of the MIM part are comparable to those of the part prepared by conventional P/M method.