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

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 degrees mu m(-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 mu < 0.2. The coating structure and properties are stable to annealing up to T = 700 degrees C. After annealing at T = 900 degrees 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.