Fracture Behavior of CrN Coatings Under Indentation and Dynamic Cycle Impact

Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique （IBAMS） was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.

Microstructure and indentation toughness of Cr/CrN multilayer coatings by arc ion plating

Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and stimulate their application.SEM results confirm the clear periodicity of the Cr/CrN multilayer coatings and the clear interface between individual layers.XRD patterns reveal that these multilayer coatings contain Cr,CrN and Cr_2N phases.Because Cr layer is softer than its nitride layer,the hardness decreases with the shortening of the bilayer period(or increasing volume fraction of Cr layer).The Cr/CrN multilayer coating with 862 nm period possesses the highest indentation toughness due to a proper individual Cr and nitride layer thickness.However,for the Cr/CrN multilayer with the bilayer period of 1351 nm,it possesses the lowest toughness due to more nitride phase.The indentation toughness of Cr/CrN multilayer coatings is related with their bilayer period.A coating with a proper individual Cr and nitride layer thickness possesses the highest indentation toughness.

TiN/CrN multilayered hard coatings with TiCrN interlayer deposited by a filtered cathodic vacuum arc technique

TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized by scanning electron microscopy (SEM) and Augerelectron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests forthe multi-layered coatings. Nanoindentation tests were performed to determine the hardness andelastic modulus of the coatings as a function of the multiplayer modulation period. It was observedthat the hardness of the multilayered coatings is higher than those of either TiN or CrN singlecoatings, and it increases with decreasing modulation periods, which is consistent with predictionsfrom the Hall-Petch type strengthening mechanism, though at small modulation periods, deviation fromthe Hall-Petch relation has been observed for the multilayered coatings. The life-span of drillscoated with TiN/CrN multilayered is triple as long as that coated with TiN layer.

Structure and mechanical properties of thick Cr/Cr_2N/CrN multilayer coating deposited by multi-arc ion plating

A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelectron spectrometry(XPS), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). Hardness and adhesion were tested by nanoindentation and scratch tester, respectively. The friction properties were investigated by a reciprocating UMT-3MT ball-on-disk tribometer in air and seawater. The results showed that the multilayer coating consisted of three different layers, with Cr,Cr2N and CrN phases, respectively. Compared with CrN single layer coating, the adhesion of the multilayer coating was improved significantly, the hardness of the multilayer coating was(21±2) GPa. The corrosion resistance of the multilayer coating was also improved in artificial seawater. The friction coefficient of multilayer coating was lower than that of CrN single layer coating both in air and seawater.

Tribological Behavior of Magnesium Alloy AZ91 Coated with TiN/CrN by Arc-glow Plasma Depositing

With advantages of high specific strength, low elastic module, good damping property et al., the magnesium alloys exhibit great potential applications in aerospace. But poor wear behavior results in limited use of magnesium alloy to static components. In this study, a 2 μm thick coating with 12 sub-layers of CrN and TiN is deposited alternately on the surface of magnesium alloy AZ91 by a novel method of arc-glow plasma depositing to improve its wear resistance. The composition and microstructure of the coating layer are analyzed by means of SEM, XRD and GDS. The friction coefficient is measured by ball on disc rubbing test, and the wear rates are also calculated. The results indicate that the friction coefficient is increased, but the wear rate is dropped sharply as compared with bare metal. The surface hardness is about HK0.01 1400.

Influence of CrN Coating on Electrochemical Behavior of Plasma Nitrided Pure Titanium in Bio-simulated Environment

Titanium and its alloys are widely used as materials for bio-medical applications, such as implants. However, ions of the alloy can release to the body region and spread into the blood circulation. In this study, plasma nitriding and CrN coating techniques are used in order to overcome the problem of ion release. The objective of this study was to investigate the effects of plasma nitrided pure titanium on the structural properties and corrosion behaviors before and after CrN coating in Ringer＇s solution at 37℃. The structural properties were investigated using Scanning Electron Microscopy （SEM） and X-ray diffraction （XRD）. A diffusion layer and a compound layer composed of δ-TiN and ε-Ti2N phases were observed on the surface of nitrided pure titanium. Corrosion tests were made for the determination of electrochemical properties with the help of Potentio- stat/Galvanostat device. The results show that corrosion behaviors of untreated and treated samples have similar characteristic.