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TiAlSiN nanocomposite coatings were deposited in a closed field unbalanced magnetron sputtering system by reactive sputtering from Ti 0.475 Al 0.475 Si 0.05 targets using modulated pulsed power magnetron sputtering (MPPMS) under a floating substrate bias. The ratio of the nitrogen flow rate to the total gas flow rate ( f N 2 ) was varied from 0 to 40%. The application of MPPMS as sputtering sources was aimed at generating a high ionization degree of the sputtered material and a high plasma density by using a pulsed high power approach. When f N 2 = 0%, an amorphous-like structure Ti 0.479 Al 0.454 Si 0.066 coating was deposited with a hardness of 10 GPa. When nitrogen was added, an optimized nanocomposite structure of nc -TiAlN/ a -Si 3 N 4 formed in the TiAlSiN coating deposited at f N 2 = 10%, in which 5–10 nm TiAlN nanocrystallites were embedded in a 2–3 nm thick amorphous Si 3 N 4 matrix. As the f N 2 was increased up to 40%, the elementary composition of the coatings remained almost the same, but the grain size of nanocrystallites approached to 10–20 nm and the AlN phase gradually precipitated. A maximum hardness (H) of 33.2 GPa, a hardness to the elastic modulus (E) ratio of 0.081 and an H 3 /E* 2 ratio of 0.19 GPa were found in the coating deposited at f N 2 = 10%. The friction coefficient of the TiAlSiN coatings was around 0.8–0.9 as sliding against a Si 3 N 4 counterpart under a normal load of 0.5 N. A wear rate of 2.0 × 10 − 5 mm 3 N − 1 m − 1 was measured in the TiAlSiN coatings deposited at f N 2 = 20–40%. As only a low residual stress is found in the TiAlSiN coatings, we consider the complete phase separation is responsible for the enhanced mechanical and tribological properties of the nc -TiAlN/ a -Si 3 N 4 nanocomposite coatings. [ABSTRACT FROM AUTHOR]

Abstract: Cr–C–N coatings with different compositions, i.e. (C+N)/Cr atomic ratios (x) of 0.81–2.77, were deposited using pulsed closed field unbalanced magnetron sputtering by varying the chromium and graphite target powers, the pulse configuration and the ratio of the nitrogen flow rate to the total gas flow rate. Three kinds of nanostructures were identified in the Cr–C–N coatings dependent on the x values: a nano-columnar structure of hexagonal closed-packed (hcp) Cr2(C,N) and face-centered cubic (fcc) Cr(C,N) at x =0.81 and 1.03 respectively, a nanocomposite structure consisting of nanocrystalline Cr(C,N) embedded in an amorphous C(N) matrix at x =1.26 and 1.78, and a Cr-containing amorphous C(N) structure at x =2.77. A maximum hardness of 31.0GPa and a high H/E ratio of 1.0 have been achieved in the nc-Cr(C,N)/a-C(N) nanocomposite structure at x =1.26, whereas the coating with a Cr-containing amorphous C(N) structure had a minimum hardness of 10.9GPa and a low H/E ratio of 0.08 at x =2.77. The incorporation of carbon into the Cr–N coatings led to a phase transition from hcp-Cr2(C,N) to fcc-Cr(C,N) by the dissolution into the nanocrystallites, and promoted the amorphization of Cr–C–N coatings with the precipitation of amorphous C(N). It was found that a high x value over 1.0 in the Cr–C–N coatings is the composition threshold to the nanostructure transition. [Copyright &y& Elsevier]