To study effects of Cu addition on the sintering behavior of SUS304L stainless steel powders and mechanical properties of their sintered compacts, SUS304L, 4 mass% Cu pre-alloyed SUS304L stainless steel powders and 2 mass% Cu mixed these two powders were sintered at 1323~1523 K in vacuum after compacted at the pressure of 490 MPa. In addition to density measurement, micro structural observation and tensile test for each sintered compacts, differential scanning calorimetry and thermomechanical analysis for each powder were conducted.
As a result, the sintered compact of 4 mass% Cu pre-alloyed stainless powder showed higher density and strength than those of other powders due to the formation of small amount of liquid phase. Alloying elements of silicon and manganese in the powders considered to react with copper during sintering and resulted to form liquid phase at relatively low temperature. Moreover, pre-alloyed copper more than solubility limit also generated small amount of liquid phase which enhanced the densification and strengthening of the sintered compacts. The sintered compact of 2 mass% Cu mixed 4 mass% Cu pre-alloyed powder showed little lower tensile strength than that of the 4 mass% Cu pre-alloyed powder because copper over the solubility limit preferentially existed at the grain boundary which played the fracture path at the tensile test.