Effects of nitrogen flux on microstructure and tribological properties of in-situ TiN coatings deposited on TC11 titanium alloy by electrospark deposition

In order to improve the tribological properties of titanium alloys,the in-situ TiN coatings were prepared by electrospark deposition（ESD） on the surface of TC11 titanium alloy.The effects of nitrogen flux on the microstructure and tribological properties of TiN coatings were investigated.The results show that the coating is relative thin when the nitrogen flux is small and mainly consists of Ti2N,α-Ti,Ti O and TiN phases,and the metastable phase of Ti2N is developed due to the rapid solidification of ESD.While in excessive nitrogen flux condition,many micro-cracks and holes might be generated in the coating.In moderate nitrogen flux,the coating is mainly composed of TiN phase,and is dense and uniform（50-55 μm）.The average hardness is HV0.2 1165.2,which is 3.4 times that of the TC11 substrate.The TiN coatings prepared in moderate nitrogen flux perform the best wear resistance.The wear loss of the coating is 0.4 mg,which is 2/9 that of the TC11 substrate.The main wear mechanisms of the coatings are micro-cutting wear accompanied by multi-plastic deformation wear.

Effect of Al and Si additions on microstructure and mechanical properties of TiN coatings

Ti-X-N (X=Al,Si or Al+Si) coatings were grown onto cemented carbide substrates by cathodic arc evaporation. The hardness of the coatings was obtained by nanoindentation and the microstructure was investigated by XRD,XPS and SEM. Solid solution hardening results in a hardness increase from 24 GPa for TiN to 31.2 GPa for TiAlN. The higher hardness values of 36.7 GPa for TiSiN and 42.4 GPa for TiAlSiN are obtained by the incorporation of Si into TiN (TiAlN) coatings due to the formation of special three-dimensional net structure consisting of nanocrystalline (nc) TiN (TiAlN) encapsulated in an amorphous (a) Si3N4 matrix phase. Furthermore,the nc-TiAlN/a-Si3N4 coating shows the best machining performance.

Effect of Rare Earth Element Cerium on Mechanical Properties and Morphology of TiN Coating Prepared by Arc Ion Plating

TiN coatings were deposited on polished substrates of W18Cr4V high speed steel by means of vacuum arc ion plating. The effect of cerium on adhesion between TiN coating and substrate was studied. The microstructures and composition of TiN coatings were also investigated by means of scanning electron microscope (SEM), Auger electron spectroscopy (AES), and X ray diffraction (XRD) technique. It was found that cerium is an effective modifying agent and the addition of suitable amount of cerium to TiN coatings can produce relatively excellent properties such as micro hardness, wear resistance, oxidation resistance and porosity. The experimental results show that the added cerium in TiN coatings makes a contribution to form the preferred direction along with a (111) or (222) close packed face, which may be one of the reasons that improves some properties mentioned above.

IMPROVEMENT OF ADHESION BETWEEN ION PLATED TiN COATING AND BASE METAL BY ADDING Y

The adhesion between the ion plated TiN coating and the base metal is improved by adding Y.The machenism of the effect of Y has been discussed as well.

Reactive Plasma Sprayed TiN Coating and Its Thermal Stability

TiN coating was prepared by reactive plasma spraying in the Ar and N2 containing plasma jet. The resuits of XRD show that the TiN coating consists of TiN and Ti3 O, neither Ti2 N nor TiO2 phases. The toughening mechanism was characterized by analyzing the SEM morphologies of the TiN coating＇s indentation of microhardness and fracture surfaces. The results indicate that the coating possesses a high toughness. The adhesion strength among the TiN layers is 25.88 MPa, which is slightly lower than that of the Ni/AI bonding coating. The oxidation process of the RPS TiN coating is TiN→Ti3 O→TiO2.

The Stress Distribution and Thermal Behavior of TiBN and TiBN TiN Coatings in Milling AISI H13 Work Tool Steel

The FEM model of TiBN and TiBN/TiN coated cutting tool in milling of H13 steel w as developed. Process variables such as temperature and stress in the coating l ayer as well as in the substrate were analyzed. The efficacy of the present FEM analysis was verified by conducting controlled milling experiments on AISI H13 t o collect the relevant tool life and force data.The results show that the stress in a coated tool can significantly be reduced compared to an uncoated cutting t ool,possibly due to surface coatings improving the tribological properties of cu tting tools.Coatings with good thermal properties also help to improve the therm al behavior of cutting tool.

Microstructure and corrosion resistance of sputtered TiN coatings on surface of Zr-4 alloy

To improve the oxidation resistance and corrosion resistance of Zr-4 alloy, titanium nitride （TIN） coatings were prepared on the Zr-4 alloy with a TiN ceramic target with different ratios of N2. Microstructure and high-temperature properties of the TiN coated samples were studied by scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction meter （XRD）, X-ray photoelectron spectroscopy （XPS）, heat treatment furnace and autoclaves, respectively. The x value of the TiN coatings （TiN） ranges from 0.96 to 1.33. After the introduction of N2, TiN coating exhibits a weak （200） plane and a preferred （111） orientation. The coating prepared with an N2 flow ratio of 15% shows an optimal oxidation resistance in the atmospheric environment at 800 ℃. In either 1 200 ℃ steam environment for one hour, or deionized water at 360 ℃ and a pressure of 18.6 Mpa for 16 d, the opitimized TiN coated samples have no delamination or spallation; and the gains in the masses of samples are much smaller than Zr-4 alloy. These results demonstrate the effectiveness of the optimized TiN coating as the protective coating on the Zr-4 alloy under extreme conditons.

PROPERTIES OF IP-TiN COATINGS MODIFIED BY AI AND La

A modified ion-plated TiN(IP-TiN) coating has been developed by adding 6 wt-% A1 and small amounts of La.Examination of this coating showed that the adhesion between the coat- ing and substrate is remarkably improved by the La added up to 2 wt-% ,and the microhardness and wear resistance of the coating surface closely relate to the contents of La.EPMA and X-ray diffraction analysis indicated that a thick transition zone forms owing to the addition of La and A1.The phase composition and grain orientation of the coating change because of the formation of such transition zone.Thus,the properties of coating were improved.

Study on the Properties of TiN Coatings on Previously Ion-Implanted Pure Magnesium Surface by MEVVA Ion Implantation

A metal vapor vacuum arc （MEVVA） is used in ion implantation for substrate preparation before the deposition process which would ensure the improvement of mechanical properties of the coating. Ti ion is implanted into pure magnesium surface by MEVVA implanter operated with a modified cathode. Implanting energy is kept at 45 keV and dose is set at 3 ×10^17 cm^-2. TiN coatings are deposited by magnetically filtered vacuum-arc plasma source on unimplanted and previously implanted substrates. Microstructure and phase composition are analysed using scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The property of corrosion resistance of TiN coatings was studied by CS300P electrochemistry-corrosion workstation, and the main impact factor of the corrosion resistance was also analyzed.

Root cause of corrosion failure of tin coating on wire clamp in marine atmosphere

The failure cause of a tinned copper wire clamp in marine atmosphere was studied systematically by X-ray photoelectron spectroscopy,scanning electron microscopy with energy dispersive spectroscopy and electrochemical measurements.The main components of the green rust on the surface of the damaged wire clamp are SnO_(2),CuO,Cu_(2)Cl(OH)_(3) and CuCO(OH)_(2).Much of green rust distributes at the platform edge along the axial direction on the crimp connection,and severe corrosion and corrosion pits occur at the platform edge zone along the axial direction.The enriching Cl-at the marine atmosphere and the existing O_(2) in air collectively enhance the corrosion process of the tin coating and the copper matrix.Finite element model results show that the residual stress and strain of the tin coating are the largest at the platform edge along the axial direction on the crimp connection,and the corresponding electrode potential of the tin coating at this zone drops significantly.The above results indicate that the residual strain increases the driving force of the corrosion electrochemical reactions and accelerates the corrosion rate and the pit corrosion of the tin coating at this zone.

Bending mechanical properties of W/TiN/Ta composites with interfacial TiN coatings

Tungsten is one of best candidates for plasma facing materials(PFMs)in fusion reactors.But its application in fusion areas is strongly restricted by the inherent brittleness and high ductile-brittle transition temperature.To improve the toughness of W-based materials,W/TiN/Ta-laminated composites were fabricated by spark plasma sintering.Three-point bending test was performed to investigate the bending mechanical properties.Multiple crack propagation is the main crack propagation mode in W/TiN/Ta composites.Energy dissipation by interfacial debonding and crack deflection at interfaces as well as crack bridging by Ta foils and plastic deformation of Ta can contribute to the toughening of W/TiN/Ta composites.The existence of interfacial TiN coatings can act as weak points and promote interfacial debonding.TiN coatings with(111)preferred orientation are found to be conducive to the strengthening of W/TiN/Ta composites.

Effect of N_(2) partial pressure on comprehensive properties of antibacterial TiN/Cu nanocomposite coating

Foreign body reactions to the wear debris and corrosion products from the implants,and bacterial infections are the main factors leading to the implant failures.In order to resolve these problems,the antibacterial TiN/Cu nanocomposite coatings with various N_(2) partial pressures were deposited on 304 stainless steels(SS)using an arc ion plating(AIP)system,named TiN/Cu-x(x=0.5,1.0,1.5 Pa).The results of X-ray diffraction analysis,energy-dispersive X-ray spectroscopy,and scanning electron microscopy showed that the N_(2) partial pressures determined the Cu contents,surface defects,and crystallite sizes of TiN/Cu nanocomposite coatings,which further influenced the comprehensive abilities.And the hardness and wear resistances of TiN/Cu coatings were enhanced with increase of the crystallite sizes.Under the co-actions of surface defects,crystallite sizes,and Cu content,TiN/Cu-1.0 and TiN/Cu-1.5 coatings possessed excellent corrosion resistance.Besides,the biological tests proved that all the TiN/Cu coatings showed no cytotoxicity with strong antibacterial ability.Among them,TiN/Cu-1.5 coating significantly promoted the cell proliferation,which is expected to be a novel antibacterial,corrosion-resistant,and wear-resistant coating on the surfaces of medical implants.

Microstructure and mechanical properties of TiN/TiAlN multilayer coatings deposited by arc ion plating with separate targets

TiN/TiAlN multilayer coatings were prepared by arc ion plating with separate targets. In order to decrease the unfavorable macroparticles, a straight magnetized filter was used for the low melting aluminium target. The results show that the output plasmas of titanium target without filter and aluminium target with filter reach the substrate with the same order of magnitude. Meanwhile, the number of macropartieles in TiN/TiAlN multilayer coatings deposited with separate targets is only 1/10-1/3 of that deposited with alloy target reported in literature. Al atom addition may lead to the decrease of peak at （200） lattice plane and strengthening of peak at （111） and （220） lattice planes. The measured hardness of TiN/TiAlN multilayer coatings accords with the mixture principle and the maximum hardness is HV2495. The adhesion strength reaches 75 N.

Structure and wear resistance of TiN and TiAlN coatings on AZ91 alloy deposited by multi-arc ion plating

In order to investigate the microstructure of TiN and TiAlN coatings and their effect on the wear resistance of Mg alloy, TiN and TiAlN coatings were deposited on AZ91 magnesium alloy by multi-arc ion plating technology.TiN and Ti70Al30N coatings were prepared on the substrate,respectively,which exhibited dark golden color and compact microstructure.The microstructures of TiN and Ti70Al30N coatings were investigated by X-ray diffractometry(XRD)and scanning electron microscopy(SEM).The micro-hardness and wear resistance of TiN and Ti70Al30N coatings were investigated in comparison with the uncoated AZ91 alloy. The XRD peaks assigned to TiN and TiAlN phases are found.The hardness of TiN coatings is two times as high as that of AZ91 alloy, and Ti70Al30N coating exhibits the highest hardness.The wear resistance of the hard coatings increases obviously as result of their high hardness.

Effects of surface roughness of substrate on properties of Ti/TiN/Zr/ZrN multilayer coatings

Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.

Microstructure and tribocorrosion performance of nanocrystalline TiN graded coating on biomedical titanium alloy

A nanocrystalline TiN graded coating was prepared on Ti6Al4V alloy by DC reactive magnetron sputtering method. The microstructure and mechanic properties of the coating were investigated. The electrochemical corrosion and tribocorrosion of the coated specimens in physiological environment were compared with those of Ti6Al4V substrate. The results show that the gradient distribution of nanocrystalline TiN is favorable for releasing the inner stress in the coating, which increases adhesion strength to 90 N. The compact structure and refined-grains of the coating result in the surface nanohardness of 28.5 GPa. The corrosion protection efficiency of the nanocrystalline TiN coating reaches 96.6%. The tribocorrosion resistance of the coating increases by 100 times in comparison with that of Ti6Al4V substrate. The high chemical stability and H3/E2 ratio (where H is hardness, and E is elastic modulus) of the nanocrystalline TiN coating are responsible for good corrosion and wear resistances.

A novel approach for evaluation of load bearing capacity of duplex coatings on aluminum alloy using PLS and SVR models

Duplex NiP/TiN coatings consisting of the electroless intermediate layers and the physical vapor deposition(PVD) top layers were fabricated on the AA6061 aluminum alloy in order to enhance the load bearing capacity. The main objective of this study was to model the load bearing based on the thickness, adhesion and elastic modulus of the coatings. For this purpose, partial least square(PLS) and support vector regression(SVR) approaches were employed.The results showed that both models had an acceptable performance;however, the PLS model outperformed SVR. The correlation coefficients between thickness, adhesion and elastic modulus with load bearing were 0.841, 0.8092 and 0.7657, respectively;so, thickness had the greatest effect on the load bearing capacity. The composition and structure of the samples were evaluated using XRD and SEM. The load capacity of the coated samples was also discussed based on the wear and adhesion evaluations. Dry sliding wear tests, under a load of 2 N and a sliding distance of 100 m,demonstrated the complete destruction of the coated specimens with low load capacity. The samples with high load capacity showed not only a superior tribological performance, but also a remarkable adhesion according to the Rockwell superficial hardness test.

AFM Analysis of TiN, TiAlN, and TiAlSiN Coatings Prepared by Cathodic Arc Ion Plating

The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP（cathode arc ion plating）, the surface morphologies and phases were analyzed with FESEM（field emission scanning electron microscopy）, and XRD（X-ray diffraction）, respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM（atomic force microscope）. The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN＋TiAlN, TiN＋Si_3N_4＋TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength（102-103 nm）, the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength（〉103 nm）.

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.

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.