Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance

Abstract

Multicomponent carbide thin films of (CrNbTaTiW)C (30–40 at.% C) with different metal contents were deposited at different temperatures using non-reactive DC magnetron sputtering. The lattice distortion for the metal lattice was estimated to vary from about 3 to 5%. Most films crystallized in the cubic B1 structure but Ta/W-rich films deposited at 600 °C exhibited a tetragonal distortion. X-ray diffraction results show that near-equimolar films exhibited a strong (111) texture. In contrast, Ta/W-rich films exhibited a shift from (111) to (100) texture at 450 °C. The in-plane relationship was determined to MC(111)[-12-1]//Al2O3(001)[110] with a lattice mismatch of about 11% along the Al2O3[110] direction. A segregation of Cr to the grain boundaries was observed in all films. The microstructure was found to be the most important factor for high hardness. Less dense Nb-rich and near-equimolar films deposited at low temperatures exhibited the lowest hardness (12 GPa), while very dense Ta/W-rich high temperature films were found to be the hardest (36 GPa). No correlation was found between the lattice distortion and the hardness. Corrosion studies revealed that the multicomponent films exhibited excellent corrosion resistance, superior to that of a reference hyper-duplex stainless steel, in 1.0 M HCl. Keywords: High entropy alloys, Multicomponent carbides, Epitaxial, CrNbTaTiW, Sputtering, Hardness