Tian Canxin

Effects of Bias Voltage on the Structure and Mechanical Properties of Thick CrN Coatings Deposited by Mid-Frequency Magnetron Sputtering ∗

Thick CrN coatings were deposited on Si (111) substrates by electron source assisted mid-frequency magnetron sputtering working at 40 kHz. The deposition rate, structure, and microhardness of the coatings were strongly influenced by the negative bias voltage (Vb). The deposition rate reached 8.96 μm/h at a Vb of −150 V. X-ray diffraction measurement revealed strong CrN (200) orientation for films prepared at low bias voltages. At a high bias voltage of Vb less than −25 V both CrN (200) and (111) were observed. Large and homogeneous grains were observed by both atomic force microscopy and scanning electron microscopy in samples prepared under optimal conditions. The samples exhibited a fibrous microstructure for a low bias voltage and a columnar structure for Vb less than –150 V.

Structure and Mechanical Properties of CrN Thick Films Deposited by High-Rate Medium-Frequency Magnetron Sputtering

A home-made electron source assisted medium-frequency (MF) magnetron sputtering system was used to deposit thick CrN films on silicon and tungsten carbide substrates at various nitrogen flow rates with a fixed total pressure (0.3 Pa) and MF power (11.2 kW). Result from scanning electron microscopy showed that the deposited CrN films have clear columnar structure, and X-ray diffraction revealed a preferred orientation of CrN (200) for samples prepared at a rate of N2/(N2+Ar) below 60%, whereas those prepared at higher N2/(N2+Ar) rate are dominated by Cr2N. Deposition rates up to 12.5 μm/h were achieved and the hardness of the CrN coatings were in a range of 11 GPa to 18 GPa.

Structure and Mechanical Properties of CrTiAlN/TiAlN Composite Coatings Deposited by Multi-Arc Ion Plating

CrTiAlN/TiAlN composite coatings were deposited on cemented carbide by using a home-made industrial scale multi-arc ion plating system. The samples were studied by X-ray diffraction, scanning electron microscopy (SEM), microhardness and ball-on-disk testing. The properties of the CrTiAlN/TiAlN coatings were significantly influenced by the microstructure and the deposition time ratio of TiAlN over CrTiAlN layers. With the increase of deposition time ratio, the microhardness of CrTiAlN/TiAlN increased from 28.6 GPa to 37.5 GPa, much higher than that of CrTiAlN coatings. The friction coefficients of the CrTiAlN/TiAlN coatings were higher than those of CrTiAlN coatings against a cemented carbide ball. The microhardness of the CrTiAlN/TiAlN coatings was changed after annealing at 800°C, and the friction coefficients of the annealed coatings were increased against the cemented carbide ball.

Influences of Bias Voltage and Target Current on Structure, Microhardness and Friction Coefficient of Multilayered TiAlN/ CrN Coatings Synthesized by Cathodic Arc Plasma Deposition

Multilayered TiAlN/CrN coatings have been synthesized on stainless steel substrates by cathodic arc plasma deposition using TiAl and Cr targets. Influences of the bias voltage, cathode current ratio ITiAl/ICr, and deposition pressure on the hardness and friction coefficient of the coatings were investigated. The measurement revealed existence of two cubic phases, face-center-cubic (Cr, Al)N and (Ti, Al)N, in the coatings deposited under various bias voltages except for the coating deposited at −400 V, which is amorphous. The hardness of the coatings was strongly dependent on the ITiAl/ICr ratio and deposition pressure, and reached a maximum of 33 GPa at an ITiAl/ICr ratio of 1.0 and a pressure of 1.0 Pa. The incorporation of the element chromium can reduce the density of pinholes in the coatings and assist the optimization of deposition conditions for high quality TiAlN/CrN coatings.