Investigation on 316L/W functionally graded materials fabricated by mechanical alloying and spark plasma sintering

316L-W (Tungsten) composite materials were fabricated by spark plasma sintering (SPS) of mechanically alloyed 316L-W powders for the development of functionally graded materials (FGMs). The effect of milling parameters on the morphology of the blended 316L/W powders and its subsequent effect on the transition between 316L and W particles during the SPS process were investigated. Samples were characterized by SEM, EDS and XRD analyses. The results so obtained show that with the increase of milling time, the mechanically activated W powder particles become thinner and smoother, with some broken fragments aggregated or inserted in the severely deformed 316L particles. A further SPS process under the conditions of 1050 °C × 45.5 MPa × 5 min leads to the densification of the powder compact and the formation of a distinguishable gray belt surrounding the retained W particles. Such a belt, which has a width of about 2–8 μm depending on different milling parameters and mainly contains Fe₇W₆, Fe₃W₃C and Fe₂W phases, is bound to be a transitional region between the retained W particles and the 316L matrix. This favorable behavior with regards to the formation of a transitional belt, is accompanied by a substantial increase in the hardness values of the composite. - Highlights: • 316L/W FGMs are successfully fabricated via MA and SPS techniques. • Gray transitional belts that mainly contain Fe₇W₆, Fe₃W₃C and Fe₂W phases formed. • The width of the belts increased from 2 to 8 um due to different milling parameters. • The maximum micro hardness of 690.31 HV is obtained for the 5 h-milled of 316L-50W layer.