Microstructures and high-temperature tensile properties of mechanically alloyed and spark plasma-sintered 304SS-CNT composites

Abstract

We fabricated and investigated a 304 stainless steel and carbon nanotube (304SS-CNT) composite with an aim to study its microstructures and high-temperature tensile properties. 304SS powders were mixed with carbon nanotubes using ball milling and consolidated using the spark plasma sintering technique. Tensile specimens made from the consolidated samples of 304SS-CNT were tested in a temperature range from 299 K (26℃) to 773 K (500℃). An induction coil was used for high-temperature tensile tests. The yield strength and the work hardening of the 304SS-CNT sample were found to be higher than those of a sample fabricated from 304SS without carbon nanotubes for all tested temperatures. Microstructure analysis carried out using optical microscopy, scanning electron microscopy, and transmission electron microscopy showed that the 304SS-CNT sample has a microstructure significantly different from the 304SS sample, e.g. reduced grain size and many small cuboidal particles. Composition analysis using energy-dispersive spectroscopy revealed that the cuboidal particles are chromium carbides, and the chromium content is reduced in the 304SS-CNT matrix. Retained carbon nanotubes could not be observed; it is thought that the carbon nanotubes may decompose, induce the reduced grain size and chromium carbides.

Stainless steel weld metal enhanced with carbon nanotubes

“…As it can be seen in Fig. 8a, the regular 304LSS structure is presented, i.e., an austenitic matrix with precipitation of vermicular ferrite 61,62 . It can be noticed by examining the nanostructured composites that the MWCNTs are majorly responsible for some considerable microstructural modifications.…”

“…The analysis of the nanostructured composite that was processed via Mechanical Alloying indicates that there is a decrease of the ferrite phases and the grain boundaries are more susceptible to appear, like what has been described by Loayza et al 2018. Although there was no substantial modification in the average values of the alloying elements of the nanostructured composite, some chromium spikes were detected, as seen in the supplementary material, indicating the possibility of carbide formation, which may also be responsible for an apparent grain refinement in the CT-TT sample 62 . By examining the EDS mapping, the chromium influence regarding the microstructural modifications becomes more evident, as there are substantially more spikes , increasing the chromium average, followed by a decrease in the iron quantities.…”

Assembling Carbon Nanotube Architectures

“…Carbon nanotubes (CNTs), due to their multifunctional properties, are promising candidates in these fields of applications. Their high compression strength, ballistic conduction, and superhydrophobicity, as well as their light weight and high aspect ratio, make them favorable additives for composite materials such as polymers, ceramics, and metals with applications as sensors, transistors, energy and data storage devices, , solar cells, and human health devices . Most commonly, chemical vapor deposition (CVD) is used for the generation of CNTs since the amount of generated CNTs is superior compared to arc discharge or laser ablation techniques .…”