High-temperature wear resistance improvement mechanism of TiAlCrNiSiNbx high-entropy alloy films through sliding wear-induced gradient nanostructure

Abstract

TiAlCrNiSiNbx high-entropy alloy films (HEFs) with varying Nb concentrations were deposited using multi-target magnetron co-sputtering at a controlled sputtering power. At room temperature (RT), 300 ℃, 500 ℃ and 700 ℃, the average coefficients of friction (COF) and wear rates of TiAlCrNiSNbx HEFs were lower than those of TC4 alloy. TiAlCrNiSiNbx HEF with a Nb content of 12.36 at% exhibited the best wear resistance at 700 ℃. A nanocomposite layer (∼260 nm) and a plastic deformation region (∼1.2 µm) formed on the film during the wear at 700 ℃. The Al2O3, Cr2O3, SiO2, and Nb2O5 in the nanocomposite layer facilitated the formation of a dense oxide layer. The cooperative deformation effect of nanocrystalline metal oxides and amorphous phases is conducive for inhibiting strain localization and enhancing wear resistance. The grain size of the nanocomposite layer was significantly refined, with an average size of 3.98 nm. This was attributed to the grain refinement caused by the interaction of dislocations and deformation twins in the plastic deformation region, which improved the strength and hardness of the film. The gradient nanostructure of the nanocomposite layer and plastic deformation region led to a more homogeneous plastic deformation, effective inhibition of strain localization and suppression of the micro-crack.