Wear Resistance Of Thin Films Research Articles

Effects of duty cycle and pulse frequency on the fabrication of AlCrN thin films deposited by high power impulse magnetron sputtering

High power impulse magnetron sputtering (HIPIMS) is a newly developed coating technology, characterized by its ultra-high peak current and peak power density to achieve unique thin film properties, such as high hardness, good adhesion and tribological performance. In this study, an AlCr alloy target was used to deposit AlxCr1−xN coatings on various substrates by the HIPIMS technique. The aim of this work was to systematically study the microstructure evaluation and mechanical properties of AlxCr1−xN coatings as a function of duty cycle and pulse frequency. The experimental results showed that the peak power density increased linearly as the duty cycle decreased from 5% to 2% at constant frequency of 1000Hz. A maximum peak power density of 2.76kWcm−2 was achieved at the duty cycle of 2% and repetition frequency of 833Hz. A mixture of cubic and hexagonal AlxCr1−xN phases was found for each coating. The x value of AlxCr1−xN thin films changed from 0.72 to 0.75 and showed no direct relationships with duty cycle and repetition frequency. The peak power density had great influence on the microstructure evolution and altered the microstructure from coarse columnar to fine columnar structure. Re-nucleation grains were also found between columnar grains. The hardness increased with increasing frequency at constant duty cycle of 2% and reached the optimum hardness of 39.9GPa at x=0.75. Good adhesion and wear resistance was observed for each coating. The critical load increased as the repetition frequency increased from 500 to 1250Hz at the same duty cycle of 2%. Since the wear resistance for each coating was excellent, the duty cycle and pulse frequency showed limited influence on the wear resistance of thin films.

Modern methods for investigating functional surfaces of advanced materials by mechanical contact testing

Modern methods for determining the hardness, Young’s modulus, elastic recovery, adhesive/cohesive strength, friction coefficient, and wear resistance of thin films, coatings, multilayer materials, and bulk materials are considered. The experimental data obtained in instrumented indentation, instrumented scratching, and tribological tests of nanostructured and quasicrystalline coatings and composite materials are analyzed. It is noted that the elastic recovery of a number of advanced materials is higher than the elastic recovery of metal alloys by a factor of 2–3. The coefficients of sliding friction of sintered samples and thin films containing Al-Cu-Fe quasicrystals are found to be relatively low. An increase in the fraction of quasicrystalline particles to 30% in composites with an aluminum matrix leads to an increase in the wear resistance.

Principles for the tribological evaluation of intrinsic coating properties

Principles for evaluation of the abrasion resistance of thin coatings are discussed. In addition to the most obvious way of measuring the wear resistance of thin films, i.e. from shallow wear scars, two basically different principles can be distinguished to evaluate the wear resistance of a coating independently of the substrate: either the coating and the substrate are worn down together and their resistance are separated from the measured composite wear resistance using information on the load distribution between coating and substrate, or first the coating and then the substrate are worn in sequence and the retardation in wear rate caused by the coating is measured. The basic principles of these two techniques are discussed.