Superhard NbB2− thin films deposited by dc magnetron sputtering

Abstract

We have deposited weakly textured substoichiometric NbB 2−x thin films by magnetron sputtering from an NbB 2 target. The films exhibit superhardness (42 ± 4 GPa), previously only observed in overstoichiometric TiB 2 thin films, and explained by a self-organized nanostructuring, where thin TiB 2 columnar grains hinder nucleation and slip of dislocations and a B-rich tissue phase between the grains prevent grain-boundary sliding. The wide homogeneity range for the NbB 2 phase allows a similar ultra-thin B-rich tissue phase to form between thin (5-10 nm) columnar NbB 2−x grains also for films with a B/Nb atomic ratio of 1.8, as revealed here by analytical aberration-corrected scanning transmission electron microscopy. Furthermore, a coefficient of friction of 0.16 is measured for an NbB 2−x film sliding against stainless steel with a wear rate of 5 × 10 −7 mm 3 /Nm. X-ray photoelectron spectroscopy results suggest that the low friction is due to the formation of a lubricating boric acid film.

Hard and elastic epitaxial ZrB2 thin films on Al2O3(0001) substrates deposited by magnetron sputtering from a ZrB2 compound target

“…6 a)-d) shows four examples of such semicoherent grain boundaries. The B segregation tendency was also shown by Mayrhofer et al [7] and Nedfors et al [31] found for 0001-oriented TiB2.4 films and randomly oriented NbB2-x films, respectively, who reported tissue phase in all grain-boundaries throughout the film. However, our processing shows that ZrB2 films can be produced with only slight excess B at isolated grain-boundaries, and not enough B to form a continuous tissue phase.…”

Influence of boron vacancies on phase stability, bonding and structure ofMB2(M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB2type structure

“…In conclusion, the phase stability, structural parameters, electronic structure, and bonding MoB2-x (x = 0.4) was formed [5,7] and in bulk synthesis of hexagonal TaB2-x (x = 0.19) [30]. energies for all competing phases included in this work are listed in Table A2.…”

Surface structural features and wear analysis of a multilayer Ti6Al4V-B4C thin film coated AISI 1040 steel

“…Besides, DLC coated 6150 steel substrates shows high nano hardness ranging from [18][19] GPa, due to its coating adhesion on the 6150 steel as studied by Silva et al [16]. Especially TiB 2 films were deposited using magnetron sputtering revealed that higher nanohardness (48-77 GPa) as explored by Nils Nedfors et al [17].…”