The aim of the article was to investigate the effect of pulsed high-voltage bias on phase composition, surface morphology, mechanical properties, and the tribological performance of the multilayered Cr/CrN/DLC coatings prepared by the filtered cathodic arc deposition (FCAD) process. The coatings were deposited using a laboratory arc source device equipped with two macroparticle filtering systems. All coatings were deposited at substrate temperatures below 200 C. Cr/CrN/DLC multilayered coatings were analysed using X-ray photoelectron spectroscopy, a glow discharge optical emission spectrometry technique, scratch testing, nano-indentation measurements (nano-hardness and Young's modulus), and optical microscopy. Tribological tests employing a ball-on-disc tribosystem were performed in dry friction conditions in an airconditioned room (RH 50 per cent, 23 C). The results proved that the substrate bias voltage exerts a significant influence on the mechanical properties of the Cr/CrN/DLC multilayered coatings by the changing chemical composition of the DLC top layers. With an increase of bias voltage from 2 to 6 kV, the Cr content increases from 2 to 4 per cent and the sp 2 /sp 3 ratio decreases from 1.06 to 0.44. The Cr-doped DLC multilayered coatings were characterized by a very smooth surface, a low friction coefficient (0.13-0.15), moderate hardness (8-11 GPa), and a Young's modulus of 95-130 GPa. Due to the moderate adhesion strength of DLC top layers, their wear resistance was not satisfactory for real applications. In each tribological test, the delaminating process of the DLC layers was observed after approximately 200-300 load cycles. To improve the mechanical properties and adhesion of a DLC layer, the optimization of the transition and DLC layers is achieved by changing the parameters of the physical vapour deposition process.
One of the most effective ways of shaping the operating parameters of functional elements is to modify the properties of a surface layer using modern technologies of surface engineering. The prospective directions in the development of surface engineering solutions are nanomultilayer coatings that enable effective shaping of surface layer properties. A very important factor in designing properties of PVD coatings, apart from their chemical composition, is their microstructure.The paper presents the influence of the microstructure of the nanomultilayer AlN-CrN-TiN coating on their tribological properties at elevated temperatures. The research methods were concentrated on the analysis of mechanical properties, microstructure, and tribological properties at increased temperatures. The studies on mechanical properties included tests on hardness using the nanoindentation method and tests on adhesion using the scratchtest method. The analysis of microstructure was performed using scanning microscopy. The tribological properties at high temperature were examined using the ball-on-disc method. The authors indicate that the AlN-CrN-TiN layers are characterised by excellent mechanical properties and tribological resistance. In this paper, the authors confirm that the microstructure of a nanomultilayer coating is important in shaping the mechanical and tribological properties of a PVD coating.
Based on the analysis of the research directions in the field of coatings and layers with special operating properties, the production technologies of composite coatings, including the gradient, multi-layer, and multi-component coatings, should be distinct. The paper presents the results of material properties tests of a multi-layer coating Ti / TiN / TiAlNgradient / (TiAlN/VN)multinano obtained on hot working steel EN X32CrMoV3.3. The preparation of the multilayer coating was specially designed to increase the durability of forging dies in the brass forging process. The authors discuss the results of the microstructure tests for the obtained coatings (STEM+FIB) and present the hardness and Young's modulus as a function of the distance from the surface (nanoHardness Tester CSM) and the results of adhesion tests carried out using a scratch-test method. The obtained multilayer coatings were also subject to a tribological test using a tribometer tester by DUCOM.
The authors indicate that the coatings based on vanadium nitride have very high hardness and Young's modulus (HV = 32–35 GPa, E = 420–450 GPa), a much lower coefficient of friction in combination with brass than steel, and a lower stability of these parameters at elevated temperatures. According to the authors, the coating represents an interesting material solution to increase the durability of forging dies in the process of brass forging.
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