Mechanical and microstructural properties of alloyed steels produced by powder metallurgy

Keywords: Powder metallurgy, alloyed steel, microstructure, wear, fracture toughness In this study, Fe-Ni-Cu-Mo-C alloy powder with two different nickel compositions was used. Original powder mixture admixing various elements in powder form, such as ferro-molybdenum, copper, graphite and ferro-boron addition were produced by powder metallurgy (P/M) method. Powder mixtures were compacted and sintered at 1120°C in cracked ammonia atmosphere for 30 minutes. The effects of different powder addition in various ratios to starting alloy powders on microstructure and mechanical properties were investigated. Phase and porosity distributions were determined by the several analysis techniques such as optical microscopy, scanning electron microscopy (SEM), SEM/EDS and XRD. In addition to these techniques, mechanical characterizations such as wear resistance, hardness and fracture toughness tests were also carried out. Ferro-boron is evaluated that boron contributes to liquid phase sintering. However, lower density, hardness and wear resistance were obtained due to usage of lower sintering temperature. It was seen that addition of the alloying elements into the starting alloy powders affects on the microstructure and mechanical properties. Especially, addition of graphite, molybdenum, nickel and copper resulted in an increase in hardness values and wear resistance; however, an increment of carbon percentage resulted in lowering the values of fracture toughness.