The influence of carbon nanotube addition on the phase composition, microstructure and mechanical properties of 316L stainless steel consolidated by spark plasma sintering

Composites of 316L steel and carbon nanotubes (CNTs) were produced by powder metallurgy using high energy milling and spark plasma sintering. The influence of CNT content on the microstructure and the mechanical properties was studied, therefore in addition to the composite samples containing 1 and 3 wt.% CNTs, a 316L specimen without CNTs was also processed. It was found that the CNT addition resulted in a smaller grain size and a higher dislocation density in the matrix. The fraction of the Fe3C phase formed due to the CNT addition increased with increasing the CNT content. The smaller grain size, the higher dislocation density and the larger fraction of the Fe3C phase led to a higher hardness in the samples containing CNTs. At the same time, the strength determined by bending was reduced, most probably due to the weak bonding between the 316L grains and the CNTs.