CrN Coatings Research Articles

Influence of modulation period and modulation ratio on structure and mechanical properties of TiBN/CrN coatings deposited by multi-arc ion plating

TiBN/CrN multilayered superlattice coatings with modulation periods Λ (bilayer thickness) ranging from 22.5 to 4.2nm and modulation ratio R (the thickness ratio of CrN and TiBN layers) ranging from 6:1 to 3:1 were synthesized using an industrial-scale cathodic arc ion plating system in an Ar–N2 gas mixture. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindention were employed to investigate the influence of modulation period and ratio on microstructure and mechanical properties of the multilayers. The sharp interfaces and nanoscale multilayered modulation were confirmed by TEM. TiBN/CrN multilayer coatings were crystallized with orientations at the (111), (200) and (220) crystallographic planes and the microstructure was strengthened at (200) preferred orientation. The maximum hardness of 38.6GPa and elastic modulus of 477GPa were obtained at Λ=11.7nm and R=5:1. The lowest value of the friction coefficient at 0.32 sliding against a WC-Co ball was obtained at a bilayer period of 11.7nm, compared to those of the coatings with other modulation periods and monolithic coatings. The wear rate of the multilayered coatings was also lower than those of the monolithic CrN and TiBN coatings.

CrN coatings deposited by magnetron sputtering: mechanical and tribological properties

Mechanical and tribological properties of CrN coatings grown on steel substrates AISI 304 and AISI 4140 using the magnetron sputtering technique were analyzed. Coatings were grown at two pressures of work, 0.4 and 4.0 Pa. The films grown on AISI 304 at a pressure of work of 0.4 showed the highest hardness because it presented a larger grain size and lower roughness. For CrN synthesized at 0.4 Pa, the surface damage was lower during the tribological test. Adherence studies were also carried out, obtaining <em>Lc</em>1 and <em>Lc</em>2 for coatings produced at both pressures and on both substrates. Better adherence behavior was observed for films grown at a low pressure because these films were thicker (~890 nm).

Effect of Ni content on CrNiN coatings prepared by RF magnetron sputtering

CrNiN coatings with various Ni content were deposited by RF reactive magnetron sputtering from Cr–Ni alloy targets. The influence of Ni content on phase structure, preferred orientation, microstructure and hardness of the coatings was investigated. The results show that RF sputtered CrNiN coatings are mainly composed of CrN phase, present columnar growth, and have a nearly feature-less surface morphology. The preferred orientation changes from CrN(220) to CrN(111) as Ni content is increased from 2.92 to 8.79 at.%. The doped Ni can favor dense structure and improve coating surface smoothness, but cannot refine grains. The coating hardness is increased by adding 2.92 at.% Ni due to the effect of discontinuous Ni coverage on hindering grain boundary sliding, dense structure and smoother surface. As Ni content is increased to 8.79 at.%, the hardness is then decreased as a result of too much soft metal and larger grain size.

STUDY ON THE RELATIONSHIP BETWEEN VALENCE ELECTRON STRUCTURE AND COATING ORIENTED GROWTH

The coating oriented growth has attracted great attention because of its effect on coating properties. In this paper, the valence electron structures of TiN and Ni were calculated with the empirical electron theory (EET) in solid and molecules for investigating preferred orientation of nitride coatings containing Ni . The calculation results show that Ni (111), CrN (100) and TiN (100) are the maximum crystal-face electron density, respectively. In CrN (or TiN ) coatings, if Ni does not form a single nickel phase, CrN (100) (or TiN (100)) preferred orientation appears easily due to its high crystal-face electron density. When Ni exists as a single phase, CrN (100)/ Ni (111) (or TiN (100)/ Ni (111)) with the minimum crystal-face electron density difference is the most likely to appear in the coatings. Furthermore, high crystal-face electron density difference usually implies fine grain microstructure. The calculation results are consistent with the experimental results.

Microstructure and tribological behavior of multilayered CrN coating by arc ion plating

Multilayered CrN (M-CrN) coating was successfully prepared by arc ion plating method. The conventional CrN coatings were deposited under Ar+N2 working pressures of 7.8×10−1Pa and 1.6×100Pa, namely P-CrN and R-CrN respectively, for comparing the tribological behavior. M-CrN coating shows the multilayered microstructure. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) measurements evidenced the different stoichiometry between the P-CrN and R-CrN layers. The experimental results show that wear resistance of the M-CrN coatings was much better than that of the conventional CrN coatings. Instead of bulk flake-off behavior, wear mechanism of the M-CrN coating is the micro-area detachment. That is because the multilayered microstructure can inhibit the formation of cracks extended into the substrate, with the high hardness, low coefficient of friction and high H/E value.

The effect of temperature and sliding distance on coated (CrN, TiAlN) and uncoated nitrided hot-work tool steels against an aluminium alloy

Adhesion and, in particular, the transfer of aluminium alloys to the bearing surface of a die are two of the main reasons for tool failure and the poor surface quality of products, especially at elevated temperatures. The present work was focused on the EN-AW6060 aluminium alloy׳s transfer initiation and the evolution to an AISI H13 hot-work tool steel, as well as CrN and TiAlN coatings in a cross-cylinder, single-pass, dry-sliding contact at room (20°C) and elevated temperatures (300–500°C). The contact was investigated in terms of the surface area and volume of the transferred aluminium alloy to the tool steel׳s surface, the topography of the wear trace and the corresponding change in the coefficient of friction. The results show a strong dependence of the tribological properties of the investigated materials on the temperature and only a limited dependence on the sliding distance, especially for the TiAlN coating. At room temperature the lowest coefficient of friction and the smallest amount of material transfer were measured for the TiAlN coating. At higher temperatures both the CrN and TiAlN coatings showed similar friction values and amounts of transferred aluminium alloy, while the nitrided hot-work tool steel exhibited an inferior tribological performance.

Adhesion of Cr/CrN Multilayers to Steel Substrates

Cr/CrN multilayers with a bilayer period λ = 62 ÷ 1000nm, were investigated. They were deposited by PLD technique on austenitic and ferritic stainless steel substrates. Coating hardness and adhesion to substrates were measured by nanoindentation and scratch testing. Multilayer properties were compared with single Cr and CrN coatings. The 2xCr/CrN and 4xCr/CrN multilayers exhibited hardness slightly lower than the hardness of a single CrN coating, while the critical load of the 4xCr/CrN multilayer, measured in the scratch test, was two times higher than for CrN. Furthermore, the character of coating failure also indicates the higher fracture toughness of multilayers than ceramic ones. The highest scratch resistance of the hardest multilayer with a bilayer period λ = 250nm is extremely interesting. The measured values of the critical loads LC1and LC2of all coatings were higher for harder ferritic than austenitic substrates. However, analysis of scratch track geometry indicated that coating failure occurred under the same deformation of the coating-substrate system, while the higher values of critical load for coatings on ferrite derived from the higher hardness of the substrate.

Substrate effect on wear resistant transition metal nitride hard coatings: Microstructure and tribo-mechanical properties

Four types of different hard transition metal nitrides (TMN:ZrN, CrN, WN and TiN) coatings were deposited on Si (100) and 316LN stainless steel substrates using DC magnetron sputtering. A comprehensive study of microstructure and substrate dependent tribo-mechanical properties of TMN coatings was carried out. Higher hardness (H) and elastic modulus (E) were obtained for WN (H=40GPa and E=440GPa) and TiN (H=30GPa and E=399GPa) coatings. This is related to the formation of (100) and (111) preferred orientations in WN and TiN coatings, respectively. However, the less hardness and elastic modulus were obtained for ZrN and CrN coatings where (200) orientation is preferred. Remarkably, low friction coefficient (0.06–0.57) and higher wear resistance in the coatings deposited on steel substrates are directly associated with the higher resistance to plastic deformation (H3/E2) and the presence of intrinsic compressive stress. Three body wear modes enhanced the friction coefficient (0.15–0.62) and the wear rate in the coatings deposited on Si substrates. This is primarily associated with low fracture toughness of brittle single crystalline Si (100) substrates. Steel-on-steel contact was dominated in ZrN/steel sliding system. This occurs due to the severe adhesive wear mode of steel ball, whereas, the abrasive wear modes were attained for the CrN, WN and TiN coatings sliding against steel balls.

Doping carbon to improve the tribological performance of CrN coatings in seawater

CrN and CrCN coatings were deposited by the cathodic arc ion plating technique. Microstructures, mechanical properties and tribological performances of the CrN and CrCN coatings in ambient air, distilled water and seawater were comparatively investigated. Results showed that the amorphous carbon and carbides were formed in the CrCN coating. The CrCN exhibited lower friction and wear than the CrN in these three environments. The lower friction performance of the CrCN coating was closely related to the self-lubricating amorphous carbon phase. While, the better anti-wear performance in seawater could be attributed to the superior mechanical properties, the better anti-corrosion performance and the lower friction shear.

Potentiality of triboscopy to monitor friction and wear

Triboscopy was proposed over 20 years ago, but despite the powerful insight it brings to analyse friction and wear with temporal evolution of localised events, its use is still limited. In this paper, triboscopy has been further developed. A LVDT sensor measures the position of the counter-body inside the wear track in a reciprocating tribometer. A high frequency acquisition system allows 10 points to be acquired within the elastic contact width, calculated by Hertz equations. The necessary number of acquired points is computed as a function of reciprocating frequency and stroke length, which enables to represent inherent details of the phenomena involved without producing excessively large files. Triboscopic maps of the acquired data are generated, where colours quantify the Z variable under measurement, X is the position of the counter-body within the wear track and Y is the number of cycles. Four examples where the use of 3D colour maps has helped to visually phenomena that would be hard to detect otherwise are presented. First, sintered composites containing solid lubricant particles dispersed in a Fe–Si–C matrix were tested. Under dry sliding, triboscopic friction maps showed higher friction at the ends of the strokes, which was more significant for harder specimens. Evidence showed that this friction increase was due to the accumulation of wear debris at the ends of the wear tracks. Second, triboscopic images of reciprocating tests of DLC–CrN coatings clearly indicated the region of the wear tracks where spalling occurred. Third, bronze disks containing regularly distributed inserts composed of graphite particles dispersed in bronze presented triboscopic maps where friction decreased periodically following approximately the size and spacing of the graphite inserts. Fourth, starved lubrication tests of textured surfaces showed no effect of surface texturing on average friction, but triboscopic maps suggested a tendency for lower friction with texturing.

Investigations on the Thermo-Mechanical Properties of CrN/CrCN Gradient Coatings Using a Thermo-Dilatometric Method

The paper describes issues related to the use of dilatometric methods for the study of thermo-mechanical properties of PVD gradient coatings. Tests were conducted on three types of CrCN / CrN coatings, which differed in the nature of the change of physico-chemical parameters in the gradient transition layer, deposited on a molybdenum substrate with the use of the cathodic arc evaporation method. The scope of the experimental studies included an analysis of the changes of the thermal “extortion” of the substrate – PVD coating system during annealing processes. In parallel, for comparison purposes, a mathematical description was proposed of gradient coatings containing the transition functions of material parameters. These functions describe the changes of such parameters as the Young's modulus, the Poisson's ratio, the thermal expansion coefficient, and the density as a function of spatial variables. Using the mathematical description proposed, numerical calculations of the state of thermal stress and strain for coatings are represented, respectively, by the transition function forms (a stepped, square, and square root) were carried via FEM. Based on the experimental and computational results obtained, the comparison between the elongation of the tested samples, and the state of thermal stress and strain in the substrate-gradient coating systems analysed were all specified.

The Properties of CrSiN Coatings of Different Si Content

CrSiN coatings of different silicon content were deposited on 1Cr18Ni9Ti austenitic stainless by d.c. reactive magnetron sputtering in a closed field unbalanced system. Comparative studies on microstructure and mechanical properties between CrN and CrSiN coatings with various Si contents were carried out. The structure of the CrSiN coatings was found to change from crystalline to amorphous structure as the Si contents increased. Amorphous phase of Si3N4 compound was suggested to exist in the CrSiN coatings. The crystalline grain became smaller in CrSiN coatings. With the increasing Si content, the coating deposition rate slew down, while the hardness of coatings improved obviously and the best hardness was about 4200 HV0.01 when the Si content was 1.13%.

Improving tribological performance of CrN coatings in seawater by structure design

Four CrN coatings were deposited on 316L stainless steel by multi-arc ion plating. The tribological behaviors of the CrN coatings were investigated by ball-on-disk tribometer in seawater. The microstructure and wear track were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and profilometer. The result shows delamination is critical to wear failure of CrN coatings in seawater and micro-cracks play an important role in the evolution of delamination. The most effective approach to eliminate the delamination is fabricating a proper multilayer structure, which could limit crack propagation only to the layer. A comprehensive wear model is established.

Property Comparation of Ti-Based and Cr-Based PVD Nitride Coatings

In this paper, the properties of TiN, AlTiN, CrN and CrAlN coatings were studied and compared, include physical and mechanical properties and micro morphology. The result showed with addition of Al, ternary AlTiN and CrAlN coatings showed dense structure and high hardness compared with TiN and CrN coatings. Adhesion strength of the Cr-based coatings was obviously higher than Ti-based coatings, but the roughness of Cr-based coatings was less than Ti-based coatings. Concerning microstructures of the coating, better ductile and dense are the remarkable character of the AlTiN and CrAlN coatings because of the disappearation of the “drop-lets” and columnar crystals.

Modification of Surface Properties of Corrosion-Protective Molds by CrN Coatings Deposited with ICP Assisted Magnetron Sputtering

Modification of Surface Properties of Corrosion-Protective Molds by CrN Coatings Deposited with ICP Assisted Magnetron Sputtering

Improvement of an industrial tool life for minting the circulating coins

The material used to produce one baht coin in the Royal Thai Mint has been changed from cupronickel (75% Cu and 25% Ni) to nickel-electroplated steel, not only for economic reasons but also for the durable properties of the latter. As a result, the higher hardness value of the new material (110 HV30 versus 80 HV10) combined with the high accuracy requirements of the coin detail have reduced the durability and lifetime of coining tools. The number of coins produced by a single coining tool was reduced from approximately 300,000 to only 40,000 coins. However, the tool life can be increased if proper selections of tool material and hard thin film coating technique are made. Two types of tool material were selected: cold working tool steel, 0.97% C and warm working tool steel, 0.5% C. CrN, TiN and TiCN coatings were examined using physical vapour deposition (PVD). It was determined that the type of tool material, the type of coating material, the coating temperature and the coating thickness influenced the lifetime of a coining tool. For the conditions studied, a 3-µm-thick TiN coat on warm working tool steel produced under a coating temperature of 400°C provided the maximum tool life up to 1.22 million strokes.

A Comparative Study on the Hardness of CrN, CrC and CrCN Coatings

Improving the surface quality of various machine components can extend their lifespans by several orders of magnitude. Thin film coating is one approach that can be used to enhance machine part surface quality. In this work, three different thin film coatings (i.e, CrN, CrC and Cr-C-N) were statistically compared for surface quality improvement of fishing-net weaving machine component, namely an upper hook. All coatings were deposited utilizing DC sputtering technique. The effects of coating types on hardness for both hardchrome and non hardchrome coated upper hooks were systematically investigated using one-way analysis of variance (ANOVA). Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to examine the surface quality of the machine component. This study found that CrN gave very high hardness values of 13.042 GPa for hardchrome coated upper hooks and 12.583 GPa for non-hardchrome coated upper hooks. However, the averages hardness of the hardchrome coated and non-hardchrome coated upper hooks were not significantly different at the 95% confidence level.

Tribological and corrosion behavior of CrN coatings: Roles of substrate and deposition defects

In this paper tribological and corrosion behavior of CrN coatings obtained through magnetron sputtering (MS) and cathodic arc evaporation (CAE) deposition techniques were studied. The effect of interfaces and defects like droplets or porosities detected with scanning electron microscope analysis, both on coating surface and cross sections, was stressed and interpreted in terms of different behavior during the electrochemical polarization tests carried out in NaCl solution or wear tests executed using a pin-on-disk tribometer. Nanoindentation measurements and scratch tests were also executed to characterize the coatings. The effect of different substrate hardness obtained changing the chemical composition of the steel bulk material was also considered, and its effect on the wear mechanisms of damaging was investigated. Regardless of the presence and distribution of the defects and the number of layers, a value of high hardness for the substrate is crucial for the long term pin-on-disk test because it can prevent the delamination of the coating. A different type of defect corresponds to a different corrosion current but, regardless of the deposition technique, the presence of a double layer ensures a better resistance to corrosion and excludes a preferential path for the localized corrosion in small areas of the steel substrate.

Compositional, Structural and Mechanical Properties of (Ti,Cr,Al)N Coatings Deposited on the Surface of Piston Rings

A novel super hard coating system of (Ti,Cr,Al)N was synthesized by multi arc ion plating technology. The Metallic ratio of Cr, Ti, and Al was varied by adjusting the currents of different TiAl target. The CrTiAlN composite coatings with different chemical composition were deposited on the surface of 65Mn steels by multi-ion plating technology in a gas mixture of Ar+N2. The coatings were characterized by means of energy dispersive X-ray(EDX) analysis, X-ray diffractmetry(XRD), scanning electronic microscopy(SEM), microhardness tester respectively. The experimental results show that the deposition velocity of CrTiAlN coatings reached maximum value, about 72nm/min. And the surface morphology of CrAlTiN films are compact and dense. The main composition of CrTiAlN composite films is Cr、Ti、Al、N, with the mass percent of Cr 29.61%,Ti 21.42%,Al 14.88%,N 34.10%. And the cross-section morphology appears as fibrous columnar crystals structure. Compared with CrN coatings, the preferential growth orientation of CrAlTiN films was changed from CrN (111) to CrN (200) after the addition of Ti, Al element. When the TiAl target arc current was 50A, the hardness reached the maximum value, 35GPa.

Electrical Resistivity of CrN Thin Films

The work is focused on the measurements of electrical resistivity of CrN thin lms deposited on glass substrates by DC-magnetron sputtering in Ar+N2 atmosphere. The studied samples reveal semiconducting behaviour of electrical resistivity in the whole range of tested preparation parameters (such as pressure and composition of ArN2 mixture), whereas the electrical transport regime is strongly in uenced by parameters of preparation. Numerical analysis of the experimental data showed that electrical transport can be adequately described in terms of variablerange hopping conduction in selected temperature intervals. Moreover, S-shaped anomaly in ρ(T ) dependence, being expected to be a consequence of phase transition to a low-temperature antiferromagnetic orthorhombic phase, has been observed for sample with the highest concentration of N2 in the temperature interval of 220 250 K. The obtained results indicate that technology processes typically used for preparation of CrN coatings represent a promising potential to develop also high sensitivity cryogenic sensors for high magnetic elds applications.