Investigation of microstructure, tribological and corrosion properties of AISI 316 L stainless steel matrix composites reinforced by carbon nanotubes

Abstract

In this study, microstructure, tribological and corrosion properties of carbon nanotubes (CNTs) reinforced hot-press sintered AISI 316 L stainless steel matrix composites were investigated. CNT nanoparticles were selected as the ideal reinforcing particle in this study since they possess high specific modulus and strength. The composite samples containing 0, 1, 2, 4 and 8 vol% CNTs were fabricated by mixing powders by high-energy ball milling and hot-press sintering under vacuum conditions at 1100 °C for 15 min under a uniaxial pressure of 48 MPa. The calculated porosities of the samples showed minor differences in the range of 4.3–5.5%, regardless of the CNT content. Microstructure investigations showed that the sintering process was successful for all produced samples. Most of the grains exhibited an almost equiaxed shape, where a slight grain refinement was observed with increasing CNT incorporation. Scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses showed that as CNT addition increased, an increasing amount of cementite (Fe3C) phase formed along the grain boundaries. Hardness and wear resistance showed continuous improvement with increasing CNT incorporation. Corrosion test results showed that the susceptibility of pitting corrosion increased as the incorporation of CNTs increased, although it was proposed that the kinetics of passive film formation was promoted by CNTs. This work will allow the use of stainless steel to be expanded, especially for applications requiring good wear resistance, while keeping corrosion resistance at acceptable levels.