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21XV International Symposium on Self-Propagating High-Temperature Synthesis
DEVELOPMENT OF FUNCTIONALLY GRADED WEAR-RESISTANT WC/a-C COATINGS BY A COMBINATION OF PULSED ARC EVAPORATION AND ELECTROSPARK DEPOSITION
K. A. Kuptsov*", A. N. Sheveyko", D. A. Sidorenko", and D. V. Shtansky"
aNational University of Science and Technology MISiS, Moscow, 119049 Russia *e-mail: [email protected]
DOI: 10.24411/9999-0014A-2019-10075
Titanium alloys are widely used due to their unique combination of high strength-to-weight ratio, melting temperature and corrosion resistance. Their main disadvantages are low wear resistance and self-adhesive wear during friction. To overcome these drawbacks, they are coated by hard PVD coatings with low friction coefficient. However, small coatings thickness, typically below 10 p,m, is not sufficient to prevent substrate deformation under high contact loads. Herein we report on a new approach of two-layer WC/C coating deposition by a combination of pulsed arc evaporation (PAE) and electro-spark deposition (ESD) [1]. In such coatings, bottom ESD layer provides superior adhesion and stiffness due to high thickness (< 100 p,m), whereas top PAE layer possesses high mechanical and tribological properties. The structure, phase and chemical composition of the obtained two-layer coatings were studied by SEM, TEM, XRD, XPS, Raman spectroscopy, and GD-OES techniques. The coatings were also characterized in terms of their mechanical (hardness, Young's modulus, elastic recovery, adhesion strength, and resistance to cyclic impact load) and tribological (friction coefficient and wear rate) properties. In addition, in situ coating mechanical tests were carried out inside transmission electron microscope using Hysitron PI 95 PicoIndenter. For the ESD sublayer, a composite structure, in which carbide grains (TiC and WCi-x with a cubic lattice of B1 type) were separated by layers of a- and P-Ti phases, was observed. The upper PAE layer, deposited either in argon or in C2H4, consisted of tungsten carbide in the form of W2C and cubic WC1-x phases. Two-layer coatings obtained under optimal conditions demonstrated high hardness of 21 GPa, low coefficient of friction in the range of 0.15-0.18 at applied loads up to 10 N, enhanced wear resistance (wear rate < 1.4 x 10-7 mm3/Nm), and superior resistance to cyclic impact loads up to 1000 N for 105 cycles.
1. K.A. Kuptsov, A.N. Sheveyko, E.I. Zamulaeva, D.A. Sidorenko, D.V. Shtansky. Two-layer nanocomposite WC/a-C coatings produced by a combination of pulsed arc evaporation and electro-spark deposition in vacuum, Mater. Des., 2019, vol. 167, 107645.
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