Superhardness effect in transition-metal diborides films

Abstract

Abstract-The structure, composition, and properties of transition metal diboride films have been studied. It was shown that they are characterized by a wide range of structural states, namely from amorphous like to nanocrystalline with crystallite sizes of 1-50 nm. The characteristic peculiarity of the structure of film tran sition metal diborides with high physical and mechanical properties is the formation of a nanocrystalline (columnar) structure with the growth texture in plane [00.1] and a nanocrystallite size of 20-50 nm. The ele ment composition of a superhard highly textured film transition metal diborides was studied by ion mass spectrometry and Auger electron spectroscopy. The overstoichiometry effect in nanocrystalline transition metal diboride films is explained. It was shown that this effect is related to the formation of an additional B⎯B covalent bond, which is realized at subgrain boundaries and leads to the appearance of superhardness in the formed coatings.

Strategy for simultaneously increasing both hardness and toughness in ZrB2-rich Zr1−xTaxBy thin films

“…[13][14][15][16][17] Recently, TM diborides have been receiving increasing attention as the next generation of refractory, hard ceramic protective thin films for replacing TM nitrides in many applications. [18][19][20][21] TM diborides are already being employed as coatings on cutting tools [22][23][24][25] and engine components, [26][27][28] as well as for use as diffusion barriers in microelectronics. [29][30][31] While TM diborides are inherently hard, that alone is not sufficient to prevent failure in applications involving high stresses, since hardness is typically accompanied by brittleness leading to crack formation and propagation.…”

Self-Similar Mode of Metals Fragmentation under Severe Plastic Deformation

“…As a result, the emerged boundary structure contains crystallites with a specific structure. Namely, according to the results of X-ray studies, those crystallites are fragmented into separate regions of coherent scattering (cells, subgrains) [1,[41][42][43].…”

Solving Strength–Toughness Dilemma in Superhard Transition-Metal Diborides via a Distinct Chemically Tuned Solid Solution Approach

“…Microindentation measurements showed that the ReB 2 possessed an average hardness of 48.0 GPa under an applied load of 0.49 N and made scratches on the surface of diamond [ 12 ]. A later work revealed that HfB 2 and TaB 2 films also reached superhard category with indentation hardness values of about 44.0 and 43.9 GPa, respectively, on specimens in their preferred growth (001) orientation [ 13 ]. Most recently, we explored the orientation-dependent superhardness of TaB 2 film and found that load-constrained deformation improves dynamic stability and leads to enhanced strength of TaB 2 (001) film, which was confirmed by an experimentally measured indentation hardness of 45.9 GPa [ 14 ].…”