Investigation of GNP effect on mechanical and morphological characteristics of liquid phase sintered SS316l nanocomposites processed via mechanical alloying and pressureless sintering

This study focuses on the development of stainless steel (SS) 316L nanocomposites reinforced with graphene nanoplatelets (GNP) employing the pressureless sintering technique. The optimal pressure of 600 MPa was used to obtain green composite samples. Composite samples with GNP weight percentages of 0.25, 0.5, and 0.75 were sintered at 1400 °C for 90 minutes under vacuum of 0.001 mbar. The effect of the GNP reinforcement on the SS316L composites was investigated by means of microstructure observations and mechanical tests. The observations of the microstructure of the composite samples revealed equiaxed and twin-grain structures, implying austenite. Grain refinement can be observed as a consequence of the addition of GNP up to 0.5 wt.% in the SS316L matrix. GNP were found to be an effective reinforcement in improving the hardness (287.7 HV) and ultimate tensile strength (554.62 MPa). However, for the 0.75 wt.% GNP composite samples, issues like agglomeration, grain coarsening, and the presence of a grain boundary precipitate (Cr7C3) resulted in a deterioration of the mechanical properties.