TC4表面TiN/Ti涂层的热腐蚀行为研究及第一性原理计算

目的综合评估涂层性能、延长压气机叶片的使用寿命,进行TiN/Ti涂层及冲蚀后TiN/Ti涂层的热腐蚀行为机制研究。方法进行了完整TiN/Ti涂层及冲蚀后TiN/Ti涂层300℃/120h的热腐蚀实验,腐蚀介质为95%(质量分数)Na_(2)SO_(4)+5%(质量分数)NaCl。冲蚀实验采用形状不规则的SiO_(2)颗粒,冲蚀角为45°,冲蚀速度为130 m/s,供砂速率为6.4 g/min。建立了完整TiN涂层、表面具有孔洞的TiN涂层及表面具有Ti液滴的TiN涂层3种第一性原理腐蚀计算模型。结果TiN/Ti涂层热腐蚀后,液滴处发生氧化并且变得疏松;样品切割边缘产生腐蚀锈迹,最终出现鼓包和裂纹;冲蚀后,涂层表面的完整性受到破坏,相较于未冲蚀区域,冲蚀坑周围更容易出现腐蚀。在热腐蚀过程中,SO_(4)^(2-)中的O和完整TiN涂层中的Ti以及液滴中的Ti电子云团接触,存在电荷转移及成键倾向,具体为Ti失电子、O得电子,腐蚀主要发生在SO_(4)^(2-)中的O与Ti之间。结论第一性原理计算结果与热腐蚀的实验结果相一致,第一性原理计算结果可以从微观上反映液滴和孔洞等缺陷对涂层热腐蚀行为的影响,能够为分析涂层的热腐蚀机制提供理论依据。

基于机械干态颗粒涂层技术制备cBN@TiN粉体

采用机械干态颗粒涂层技术分别制备了cBN@TiO_(2)(TiO_(2)包覆立方氮化硼)粉体和cBN@(TiO_(2)+C)(TiO_(2)+碳包覆立方氮化硼)粉体,然后在1600℃、N_(2)气氛下进行高温热处理制备cBN@TiN(TiN包覆立方氮化硼)粉体,研究了高温热处理前后粉体的物相组成与微观形貌以及高温反应机理。结果表明:机械干态颗粒涂层技术可以使纳米TiO_(2)和纳米TiO_(2)+C颗粒均匀包裹在cBN颗粒表面。在高温热处理过程中,TiO_(2)与cBN反应生成液相B_(2)O_(3),促进了cBN相变成六方氮化硼(hBN),cBN的高温稳定性差,以cBN@TiO_(2)为原料制备的cBN@TiN粉体颗粒表面形成由TiN相和hBN相组成的片状结构层;当存在碳时,TiO_(2)会优先与碳发生还原反应生成TiN,抑制B_(2)O_(3)的生成,从而降低cBN相变量,此时cBN的高温稳定性好,以cBN@(TiO_(2)+C)为原料制备的cBN@TiN粉体颗粒表面形成主要为TiN相的颗粒结构层。

TLM钛合金表层TiN/Sn复合涂层的制备及磨损行为研究

为了提高Ti-25Nb-3Zr-2Sn-3Mo(TLM)钛合金的耐磨性能,采用表面机械复合强化(SMCS)工艺在合金表层制备了复合涂层并研究了复合涂层的显微组织、微观力学性能和摩擦学性能。结果表明:采用表面机械复合强化技术可在合金表层成功制备TiN/Sn复合涂层,随着Sn含量的增加,复合涂层的厚度和粗糙度不断增大,10%、20%、30%、40%Sn涂层的厚度分别为9.08、14.05、18.33、23.55μm;10%、20%、30%、40%Sn涂层的表面硬度分别为590、529、465、400 HV,相比基体硬度(~230 HV)有所提高。复合涂层的磨损量随Sn含量的增加先减小后增大,20%Sn样品具有最低的磨损量;在干磨损试验中,原样的磨损机制以黏着磨损为主,同时伴随磨粒磨损,复合强化样的磨损机制为磨粒磨损、黏着磨损,同时伴随氧化磨损。

Pitting corrosion behavior and corrosion protection performance of cold sprayed double layered noble barrier coating on magnesium-based alloy in chloride containing solutions

Nitrogen processed, cold sprayed commercially pure(CP)-Al coatings on Mg-based alloys mostly lack acceptable hardness, wear resistance and most importantly are highly susceptible to localized corrosion in chloride containing solutions. In this research, commercially pure α-Ti top coating having good pitting potential(~1293 mV_(SCE)), high microhardness(HV_(0.025): 263.03) and low wear rate was applied on a CP-Al coated Mg-based alloy using high pressure cold spray technology. Potentiodynamic polarization(PDP) curves indicated that the probability of transition from metastable pits to the stable pits for cold spayed(CS) Al coating is considerably higher compared to that with the CS Ti top coating(for Ti/Al/Mg system). In addition, CS Ti top coating was in the passivation region in most pH ranges even after 48 h immersion in 3.5 wt% NaCl solution. The stored energy in the CS Ti top coating(as a passive metal) was presumed to be responsible for the easy passivation. Immersion tests indicated no obvious pits formation on the intact CS Ti top coating surface and revealed effective corrosion protection performance of the CS double layered noble barrier coatings on Mg alloys in 3.5 wt% NaCl solution even after 264 h.

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.

TiC-Fe coatings prepared by flame spray synthesis process

A new process, flame spray synthesis (FSS), has been developed for producing ceramic containing composite coatings. By combining self propagation high temperature synthesis (SHS) and flame spraying, the cermet based material was synthesized and deposited simultaneously. TiC Fe coatings were deposited from commercial ferrotitanium, iron and graphite powders by the flame spraying synthesis process. Microstructure analyses revealed that TiC was synthesized during spraying, and that submicron and round TiC particles were dispersed within an iron matrix. Flame spray synthesized coatings were composed of alternate soft and hard layers, whose hardness were 3.0～6.0 GPa and 11～13 GPa, respectively.

Pulsed DC plasma enhanced chemical vapor deposited TiN/Ti(C,N) multilayer coatings

TiN single coatings and TiN/Ti(C,N) multilayer coatings deposited on Cr12MoV substrate have been completed by pulsed DC plasma enhanced chemical vapor deposition(PCVD) process. The SEM, XRD and microvicker’s hardness as well as the indentation test were used to study the microstructure and mechanical properties of TiN/Ti(C,N) multilayer coatings. The results show that TiN/Ti(C,N) coatings are fine and have free column structure, and carbon atoms take the place of some nitrogen atoms in Ti(C,N) coatings when lower flow ratio of CH 4 is used. The microvicker’s hardness and interfacial adhesion between TiN/Ti(C,N) coatings and Cr12MoV substrate increases more obviously than that of TiN single hard coatings due to the more dense and free column structure when process is optimized.

Salt spray corrosion test of micro-plasma oxidation ceramic coatings on Ti alloy

Ceramic coatings were prepared on Ti-6Al-4V alloy in NaAlO2 solution by micro-plasma oxidation （MPO）. The salt spray tests of the coated samples and the substrates were carded out in a salt spray test machine. The phase composition and surface morphology of the coatings were investigated by XRD and SEAM. Severe corrosion occurred on the substrate surface, while there were no obvious corrosion phenomena on the coated samples. The coatings were composed of Al2TiO5 and a little α-Al2O3 and mille TiO2, and the salt spray test did not change the composition of the coatings. The weight loss rate of the coatings decreased with increasing MPO time because of the increase in density and thickness of the coatings. The surface morphology of the coatings was influenced by salt spray corrosion test. Among the coated samples, the coating prepared for 2 h has the best corrosion resistance under salt spray test.

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.

Influence of Si Content on Properties of Ti1-xSixN Coatings

To investigate the evolution of microstructure and wear behavior of TiSiN coatings with the variation of Si in targets and lays the foundation for its controllable mass production, Ti1-xSixN composite coatings were deposited onto Si(100) and cemented carbide substrates using TiSi targets with different Si content by cathodic arc ion plating. The influences of Si on the microstructure and mechanical properties were studied. Nano-amorphous composite structure appeared in the Ti1-xSixN coatings when Si content in TiSi target was higher than 5 at%. However, further increase of Si content in TiSi target exhibited a negligible effect on the microstructure of Ti1-xSixN coatings. Hardness and deformation resistance were correlated to the content of Si in TiSi targets. Maximum hardness was obtained as the Si content in target increased up to 20 at%. Friction coefficient and wear rate significantly decreased with addition of Si in TiN coating, and then dually increased with the increase of Si content in targets.

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）.

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.

Improvement on the Oxidation Resistance of a Ti_3Al Based Alloy by Cr1-xAl_xN (0≤x≤0.47) Coatings

Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3＋Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.

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.

Microstructural and tribological behavior of TiAlN/MoS_2-Ti coatings

A TIA1N/MoS2-Ti coating was developed to improve the tribological characteristics of a single TiAlN coating. The MoS2-Ti layer was deposited by a DC magnetron sputtering system on the hard TiAIN coated SKD-11 steel substrate. The titanium content in the MoS2-Ti layer was 11.3 at.% determined by EPMA. The surface morphology was observed by FE-SEM. The TiAlN layer exhibited excellent adhesion and hardness. However, the deposition of an MoS2-Zi layer on the TRAIN led to a significant improvement in tribological properties without affecting the adhesion to the substrate. The MoS2-Ti layer significantly decreased the friction coefficient of the TiAIN coating, and the drop was 48% after MoS2-Ti deposition. Also, the MoS2-Ti layer remarkably decreased the wear rate of the TtA1N coating.

Microstructure evolution and mechanical properties of Ti-B-N coatings deposited by plasma-enhanced chemical vapor deposition

Ternary Ti-B-N coatings were synthesized on AISI 304 and Si wafer by plasma-enhanced chemical vapor deposition (PECVD) technique using a gaseous mixture of TiCl4,BCl3,H2,N2,and Ar.By virtue of X-ray diffraction analysis,X-ray photoelectron spectroscopy,scanning electron microscope,and high-resolution transmission electron microscope,the influences of B content on the microstructure and properties of Ti B N coatings were investigated systematically.The results indicated that the microstructure and mechanical properties of Ti-B-N coatings largely depend on the transformation from FCC-TiN phase to HCP-TiB2 phase.With increasing B content and decreasing N content in the coatings,the coating microstructure evolves gradually from FCC-TiN/a-BN to HCP-TiB2 /a-BN via FCC-TiN+HCP-TiB2/a-BN.The highest microhardness of about 34 GPa is achieved,which corresponds to the nanocomposite Ti-63%B-N (mole fraction) coating consisting of the HCP-TiB2 nano-crystallites and amorphous BN phase.The lowest friction-coefficient was observed for the nanocomposite Ti-41%B-N (mole fraction) coating consisting of the FCC-TiN nanocrystallites and amorphous BN

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.

Microstructure and physical properties of PVD TiN/(Ti, Al)N multilayer coatings

Magnetron sputtered (Ti, Al)N monolayer and TiN/(Ti, Al)N multilayer coatings grown on cemented carbide substrates were studied by using energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy(SEM), nanoindentation, Rockwell A indentation test, strength measurements and cutting tests. The results show that the (Ti, Al)N monolayer and TiN/(Ti, Al)N multilayer coatings perform good affinity to substrate, and the TiN/(Ti, Al)N multilayer coating exhibits higher hardness, higher toughness and better cutting performance compared with the (Ti, Al)N monolayer coating. Moreover, the strength measurement indicates that the physical vapour deposition (PVD) coating has no effect on the substrate strength.

Effect of Sputtered TiAlCr Coatings on Oxidation and Hot Corrosion Resistance of Ti-24Al-14Nb-3V

The effect of sputtered Ti-50Al-10Cr and Ti-50A1-20Cr coatings on both isothermal and cyclic oxidation resistance at 800-900℃ and hot corrosion resistance at 850℃ of Ti-24Al-14Nb-3V was investigated. Results indicated that Ti-24Al-14Nb-3V alloys exhibited poor oxidation resistance due to the formation of Al2O3+TiO2+AlNbO4 mixed scales in air at 800-900℃ and poor hot corrosion resistance due to the spoliation of scales formed in Na2SO4+K2SO4 melts at 850℃. Both Ti-50Al-10Cr and Ti-50Al-20Cr coatings remarkably improved the oxidation and hot corrosion resistance of Ti-24Al-14Nb-3V alloy.

Effects of Electroplated Coatings on Corrosion Behavior of Ti-1023/30CrMnSiA Galvanic Couple

Galvanic corrosion behavior of Ti-1023 titanium alloy coupled 30CrMnSiA steel was investigated in 3.5% NaCl solution. Particular attention was given to the effect of three different electroplated coatings on corrosion behavior of the galvanic couple. Galvanic corrosion test was conducted on Ti-1023 titanium alloy which coupled Ni-electroplated 30CrMnSiA, Zn-electroplated 30CrMnSiA, Cd-electroplated 30CrMnSiA and bare 30CrMnSiA, respectively. Corrosion properties including open circuit potential （Eoc）, galvanic corrosion potential （Eg）, and galvanic corrosion current （lg） were monitored. Corrosion morphology was observed by optical microscope （OM） and corrosion mechanism was analyzed and discussed. The results show that the three electroplated coatings improve the corrosion resistance of the anode in different magnitudes. Ni-electroplated 30CrMnSiA and Cd-electroplated 30CrMnSiA coatings are found to be least susceptible to galvanic corrosion when coupled Ti-1023 titanium alloy. Zn-electroplated 30CrMnSiA is moderately susceptible to galvanic corrosion. But the bare 30CrMnSiA is highly susceptible to galvanic corrosion in corrosive environment.