Stainless steel weld metal enhanced with carbon nanotubes

Abstract

This paper aims to establish the most indicated route to manufacture a nanostructured powder composed of 5 wt% Multi-walled Carbon Nanotubes and 304LSS powder. Four specimens were prepared using Mechanical Alloying and Chemical Treatment (CT) with Hydrogen Peroxide ($${\mathrm{H}}_{2}{\mathrm{O}}_{2}$$ H 2 O 2 ) as the main processes. A thermal treatment post-processing was used in half of the samples to remove the remaining amorphous carbon and to evaluate its effects. Regarding the powder analysis, attachment, amorphous carbon degree, crystallinity, and doping of the CNT throughout the metal matrix were investigated. The nanostructured powders were then inserted as a core in a 304LSS tubular rod to perform the arc welding process. The CT route eliminated the amorphous carbon and generated more refiner grains, which provided a cross-section hardness gain of more than 40% regarding the 304LSS joint. In summary, the CT route, combined with the GTAW process, provided a new method for nanocomposite manufacturing by combining shorter preparation steps, obtaining an improvement in the microstructural and hardness performance.

Effects of CNTs addition on the microstructure and microhardness of stainless steel alloy/carbon-manganese non-alloyed steel welding

“…The microhardness percentages were calculated based on indentation data in topside and cross-section of WM with nanocomposite compared to its own BM. Although they using the same process, the WM/BM welding with similar materials, 6,7,13 not is appropriately compared with our results, because our WM/BM were a dissimilar materials. However, despite that is evident the reinforcement effect of the CNTs in the weld metals.…”

“…Recently, Borges et al 13 reported a microhardness increase up to 40% in the cross-section, if compared with compared to a SS 304L without CNTs clad welded by GTAW process. Moreover, this work indicates the presence of carbide formation in the microstructure of SS 304L-CNT composite, which may be responsible for grain refinement.…”

Simultaneous Improvement of the Electric Conductive and Mechanical Properties of Nanostructured Aluminum Alloy

“…4. The nanostructured powder evidenced a reduction in the intensity of the austenitic plane (111), in part due to the superposition with C(100) of the carbon nanotubes, and to the high X-ray absorption capacity of the latter, while the peak C(002) can already is be noted in the spectrum 9,10,34 . All of this proves that the nanostructured powder (304LSS-CNT) was introduced efficiently in the melting aluminum to supply elements alloys such as Fe, Cr, Ni, and Mn of the stainless-steel particles, and nanofibers (MWCNT); to improve both the mechanical properties and electric conductivity 8,12 .…”

“…2e) changed the aluminum's microstructures, creating elongated grains, with a low segregation of the Fe and of the other elements in the dendrite's limits 33 . This behavior could be associated with the combination of a decreasing of the grain size by effect to the stainless-steel particles and a uniform distribution of the carbon nanotubes in the MM, which avoids a bigger movement of the atoms by the effect of the pine with mainly Cr and Ni whose carbon affinity is great 10,17 . When the percentage of SS increase to 2 wt.% (e, j), along 0.1wt.% CNT, the microstructure was remarkably altered but no segregation was observed, as the temperature of the liquid aluminum was not enough to melt all the SS particles, which produced a deterioration of the properties of this sample 33 .…”

“…There is a high redshift for the inner (11 cm −1 ) and outer (26 cm −1 ) walls, indicated by the G inner and G outer center position. That redshift suggested a tensile strain producing a photon softening (n-doping), as the external walls presented a higher difference suggesting a great interaction with the MM, which produces a bonding between the carbon nanoparticles and the stainless-steel particles 8,10,13 . This effect was confirmed by the ∆G position (G outer -G inner ) going from 23 cm −1 (MWCNT) to 13 cm −1 (304LSS-CNT), with the low distance between the peaks indicating a high doping.…”