Abstract
Tungsten (W)-based materials attract significant attention due to their superior mechanical properties. Here, we present a chemical approach based on the addition of carbon (C) for increased strength via the combination of three strengthening mechanisms in W thin films. W:C thin films with C concentrations up to ~4 at.% were deposited by magnetron sputtering. All films exhibit a body-centred-cubic structure with strong <hh0> texture and columnar growth behaviour. X-ray and electron diffraction measurements suggest the formation of supersaturated W:C solid solution phases. The addition of C reduced the average column width from ~133 nm for W to ~20 nm for the film containing ~4 at.% C. The column refinement is explained by a mechanism where C acts as re-nucleation sites. The W film is ~13 GPa hard, while the W:C films achieve a peak hardness of ~24 GPa. The W:C films are ~11 GPa harder than the W film, which is explained by a combination of grain refinement strengthening, solid solution strengthening and increased dislocation density. Additional micropillar compression tests showed that the flow stress increased upon C addition, from ~3.8 to ~8.3 GPa and no brittle fracture was observed.
Highlights
High melting point [2] and a high radiation resistance [3]
The grains appear to be larger, but, a detailed study at higher magnification shows a fine lamellar structure suggesting a reduced grain size compared to the W film
The width of the lamella in the inset is ~15 nm and the lamellas are found between the grains that have a size that is similar to the ones in the W film
Summary
High melting point [2] and a high radiation resistance [3]. Pure W, has a high brittle-to-ductile transition temperature (BDTT) [4], which often limits the applicability of tungsten as a structural material. Many strategies have been explored to decrease the room temperature (RT) brittleness of W, with microstructure design (grain refinement) proving to be one of the most effective pathways to control the mechanical properties and attain a combination of high strength and ductility. Recent studies have demonstrated that the addition of small amounts (~5–10 at.%) of p-block elements (boron (B), carbon (C) and nitrogen (N)) is an effective chemical method to reduce the grain sizes of magnetron-sputtered thin films, without the formation of other phases such as carbides [13,14]. We have previously investigated the influence of C in magnetron sputtering of TaW-rich high entropy alloy films with the composition Ta41W41Cr3Nb12Ti3 [14], where we observed clear grain refinements and increased hardness and crack resistance, upon the addition of C. The coatings were characterised using XRD, elastic recoil detection analysis (ERDA), and electron microscopy, with the mechanical properties studied through nanoindentation and micropillar compression tests
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
