The Microstructure, Mechanical and Friction-Wear Properties of (TiB_x/TiSi_yC_z)x3 Multilayer Deposited by PLD on Steel

The microstructure, mechanical properties, and friction-wear performance of (TiB_x/TiSi_yC_z)x3 multilayer coatings deposited on the M2 steel by the pulsed laser deposition are investigated in detail in as-deposited state and after annealing at 500 °C for 5 min in air. Scanning and transmission electron microscopies are used to reveal microstructural changes caused by annealing. The influence of post-deposition annealing on hardness and Young modulus is studied in nanoindentation test. A scratch-test is applied to reveal changes in adhesion and the coefficient of friction (CoF) of coated samples with diamond before and after annealing. Friction-wear properties are also analyzed in dry sliding with Al₂O₃ and 100Cr6 steel in ball-on-disc tests. Our analysis shows that the post-deposition annealing leads to partial devitrification of the TiB_x layers, where nanocrystalline TiB₂ phase is identified, while the TiSi_yC_z layers retain amorphous. Annealing significantly increases mechanical properties of coated samples and adhesion of the (TiB_x/TiSi_yC_z)x3 multilayer to steel substrates. Friction-wear properties of coated samples are also notably improved. The values of CoF for coated samples tested with diamond (in the scratch-test), alumina, and 100Cr6 steel (ball-on-disc tests) are in the range of 0.05–0.23, while for M2 steel the CoF values are 0.8, 0.45, and 0.8, respectively.