Structural-Phase State, Elastic Stress, and Functional Properties of Nanocomposite Coatings Based on Amorphous Carbon

Resumo

The paper analyzes the microstructure and phase state of magnetron-sputtered nanocomposite Ti-C-Ni-Cr coatings based on Ni- and Cr-doped amorphous carbon by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The analysis shows that the coating structure comprises an amorphous carbon matrix and nanosized TiC and Ni particles with relatively low lattice bending-torsion (no greater than 75° µm⁻¹) and with much lower local internal stress compared to its value in superhard coatings. The microhardness of such coatings on VT1-0 titanium alloy is H = 14 GPa, and their friction coefficient is µ < 0.2. The coating structure and properties are stable to annealing up to T = 700°C. After annealing at T = 900°C, the coating surface reveals TiO, Ti₂O, and other oxide phases. The results of scratch testing show that the character and the scale of fracture in the coatings depend on the substrate hardness: on soft substrates, the coatings experiences intense cracking and delamination, and on hard alloy substrates, they undergo multifragmented fracture. The coatings on hard alloy substrates survive up to a load of 80 N.