Incorporating hard materials like diamond or carbon nanotubes (CNTs) into steel presents unique challenges, particularly when using traditional melt processing techniques. Diamond, for example, is extremely difficult to integrate into steel via melting due to its thermal instability. However, diamond is routinely embedded in steel surfaces for cutting applications. In the electronics industry, steel wires coated with diamond are used to slice silicon crystals into thin wafers.
Two main techniques are commonly employed for embedding diamond in metals:
1. Electroplating: Diamond powder is suspended in a metal ion electrolyte, usually nickel. When an electric current is applied, nickel deposits on the metal wire, trapping the diamond particles in place.
2. Sintering: For more demanding cutting tools, diamond can be embedded on metal surfaces using sintering, which fuses the particles to the substrate at high temperatures without melting the metal.
Similar challenges exist when attempting to incorporate carbon nanotubes into steel. Altering steel microstructure with nano-carbon forms via melt processing is difficult. Yet, CNTs have been successfully composited with steel using surface treatments and powder metallurgy techniques, yielding notable improvements in toughness, strength, and hardness.
Surface treatments primarily enhance surface properties.
Powder metallurgy allows CNTs to be incorporated into the steel matrix via sintering. In this process, CNTs bridge microcracks, reinforcing the steel matrix in ways that traditional carbon forms cannot.
Several studies demonstrate these effects:
* *Stainless steel weld metal enhanced with carbon nanotubes* ([Nature](https://www.nature.com/articles/s41598-020-75136-z))
* *Attempts to Modify Austenitic Steel with Carbon Nanotubes* ([IMIM](https://www.imim.pl/files/archiwum/Vol1_2022/47.pdf))
* *Surface Modification of Mild Steel by CNT Reinforcement under Electron Beam Melting* ([arXiv](https://arxiv.org/pdf/1505.02168))
* *Laser sintering of separated and uniformly distributed multiwall carbon nanotubes integrated iron nanocomposites* ([AIP](https://pubs.aip.org/aip/jap/article-abstract/115/11/113513/913673/Laser-sintering-of-separated-and-uniformly?redirectedFrom=fulltext))
* *The influence of carbon nanotube addition on 316L stainless steel consolidated by spark plasma sintering* ([ScienceDirect](https://www.sciencedirect.com/science/article/pii/S2238785418301790))
Structural, mechanical and tribological investigations of CNT-316 stainless steel nanocomposites processed via spark plasma sintering
https://www.sciencedirect.com/science/article/abs/pii/S0301679X2030356X
Synthesis and properties of graphene and graphene/carbon nanotube-reinforced soft magnetic FeCo alloy composites by spark plasma sintering
https://link.springer.com/article/10.1007/s10853-016-0041-2
These studies report varying effects some note increased hardness but reduced toughness, while others show overall property improvements. The primary challenges in working with nano-materials, including CNTs, remain dispersion and preventing aggregation within the steel matrix.
On online discussion forums like reddit skepticism still exists among metallurgists but diamond has been embedded in steel for a long time now and it seems that the technique is now being adapted to embed carbon nanotubes.
It's exciting to see how steel, a material with history going back thousands of years, is being transformed with cutting edge carbon nanomaterials. Coincidentally there have been some reports about ancient steel makers 'accidently' incorporating carbon nanotubes in their steel for example the fabled Damascus steel ,whose strength has not been reproduced by modern metallurgists, is said to have had CNT but opinions are divided.
In summary, while directly incorporating diamond or CNTs into molten steel is impractical, surface embedding and powder metallurgy techniques have proven effective in enhancing steel’s mechanical properties for specialized applications.
Original discussion on reddit
https://www.reddit.com/r/materials/comments/1oho6hf/comment/nlsclow/?context=3&utm_source=share&utm_medium=mweb3x&utm_name=mweb3xcss&utm_term=1&utm_content=share_button
https://www.reddit.com/r/materials/comments/1oho6hf/comment/nlsf3o8/?context=3&utm_source=share&utm_medium=mweb3x&utm_name=mweb3xcss&utm_term=1&utm_content=share_button
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