Structural, mechanical and tribological investigations of CNT-316 stainless steel nanocomposites processed via spark plasma sintering

Abstract

In this work, carbon nanotube (CNT) reinforced 316 L stainless steel (SS) composites were studied for the impact of CNT content on their microstructural, mechanical and tribological behaviour. Carbon nanotube-SS composites were fabricated via spark plasma sintering process at a sintering temperature of 800 °C. The tribological behaviour for pristine and 0.2, 0.5, 1.0, and 2.0 wt% CNT loaded samples was studied by a ball-on-disc tribometer under a normal load of 10 N at 28 °C and 300 °C. Microstructural studies showed grain refinement with the addition of CNT and hence enhancement in hardness and yield strength. The friction coefficients for high temperature tests were found to be lesser than that of room temperature values. Decrease in friction coefficient at high temperature tribotests compared to low temperature case could be attributed to the lubrication effect coming from local melting and CNTs. The lubrication of CNTs coming from its unique shape, aspect ratio, and flexibility. The wear rate was found to decrease with increasing CNT concentration in both cases. For the 2 wt% CNT case, the wear volume at 28 °C and 300 °C were nearly the same due to the lubrication effect. About 25% and 90% reduction in wear volume was observed for 2 wt% CNT sample at room temperature and 300 °C, respectively, when compared to their pristine counterpart. The composited samples showed increased resistance to wear than the pristine and commercial grade at both temperatures. A systematic study on the morphology, structure, hardness, yield strength, elemental composition, and tribology of the composites to understand the structure-property correlation of CNT-steel composite is presented in detail.