Investigation of the tribological characteristics of Ta–Zr–Si–B–C–N coatings

Abstract

Ta–Zr–Si–B–C–N coatings were deposited by magnetron sputtering using a TaSi2–Ta3B4–(Ta, Zr)B2 composite target. Ar, as well as Ar + N2 and Ar + C2H4 gas mixtures, were used as the working gas. The structure and composition of the coatings were studied by scanning electron microscopy, glow-discharge optical emission spectroscopy, and X-ray diffraction. A Calowear tester was used to measure the thickness and abrasion resistance of the coatings. Erosion resistance tests were carried out using a UZDN-2T (Russia) ultrasonic disperser. Tribological tests in the sliding friction mode were carried out on an HT Tribometer (CSM Instruments, Switzerland) automated friction machine. The wear zone after tribological testing was examined using a Veeco Wyko 1100 (Veeco, USA) optical profiler. The results showed that the Ta–Zr–Si–B coating was characterised by a columnar structure with an h-TaSi2 crystallite size of 11 nm. The introduction of nitrogen and carbon into the composition of the coatings led to the suppression of columnar growth and a ~2–4-fold decrease in the size of h-TaSi2 crystallites. Carboncontaining coatings demonstrated the best abrasive resistance. The sliding friction tests showed that the Ta–Zr–Si–B coating is characterised by a stable coefficient of friction of 0.3 at a temperature of 25 °C up to the maximum working temperature of 250 °C. The introduction of nitrogen led to an increase in the coefficient of friction up to 0.8–1.0 at a t = 50÷110 °С. The coating with the minimum carbon concentration showed a stable coefficient of friction of ~0.3 up to a maximum temperature of 250 °C. The best result was demonstrated by the sample containing the maximum amount of carbon, with its coefficient of friction remaining at the 0.25 level up to a temperature of 350 °C.