High temperature oxidation behavior of Ti(Al,Si)_3 diffusion coating on γ-TiAl by cold spray

A Ti(Al,Si)3 diffusion coating was prepared on γ-TiAl alloy by cold sprayed Al?20Si alloy coating, followed by a heat-treatment. The isothermal and cyclic oxidation tests were conducted at 900 °C for 1000 h and 120 cycles to check the oxidation resistance of the coating. The microstructure and phase transformation of the coating before and after the oxidation were studied by SEM, XRD and EPMA. The results indicate that the diffusion coating shows good oxidation resistance. The mass gain of the diffusion coating is only a quarter of that of bare alloy. After oxidation, the diffusion coating is degraded into three layers: an inner TiAl2 layer, a two-phase intermediate layer composed of a Ti(Al,Si)3 matrix and Si-rich precipitates, and a porous layer because of the inter-diffusion between the coating and substrate.

磁控溅射镀膜技术在(Cr,Ti,Al)N涂层上的应用

过渡金属氮化物硬质涂层在切削刀具、精密模具和机械零部件等领域有着广泛的应用。随着切削技术的进步和难加工材料的增多,硬质涂层已由传统的二元涂层向着三元、四元涂层不断发展。(Cr,Ti,Al)N四元涂层因其优异的综合性能而备受研究人员的关注。本文从磁控溅射镀膜的基本原理和技术特点出发,介绍了制备(Cr,Ti,Al)N涂层常见的磁控溅射镀膜技术,分析了采用单质靶与合金靶沉积镀膜的效果及其各自的优缺点,研究了磁控溅射工艺参数对(Cr,Ti,Al)N涂层机械性能的影响,最后讨论了(Cr,Ti,Al)N梯度涂层的作用及其制备方法。本文可为设计(Cr,Ti,Al)N涂层制备工艺、改善(Cr,Ti,Al)N涂层性能提供理论参考与指导。

制备Si-Cr-Y高温抗氧化涂层适用于低密度Nb-Ti-Al合金

针对低密度Nb-Ti-Al合金抗氧化性能需求,开展了Si-Cr-Y抗氧化涂层研究,利用SEM、EDS、电阻内热法等手段分析了制备的硅系涂层高温抗氧化性能和微观结构在氧化前后的变化。结果表明,1200℃下涂层抗氧化寿命达到133 h,室温~1200℃空冷热震大于15000次;涂层与基体之间形成一层扩散阻氧层,保证了涂层与基体之间的结合强度;在高温大气环境下,涂层表面形成一层隔绝氧气的SiO2保护层,从而表现出Si-Cr-Y涂层具有良好的抗氧化性能。

Structural characteristics and high-temperature tribological behaviors of laser cladded NiCoCrAlY−B_(4)C composite coatings on Ti6Al4V alloy

In order to improve the hardness and tribological performance of Ti6Al4V alloy,NiCoCrAlY-B_(4)C composite coatings with B_(4)C of 5%,10%and 15%(mass fraction)were fabricated on its surface by laser cladding(LC).The morphologies,chemical compositions and phases of obtained coatings were analyzed using scanning electronic microscope(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD),respectively.The effects of B_(4)C mass fraction on the coefficient of friction(COF)and wear rate of NiCoCrAlY-B_(4)C coatings were investigated using a ball-on-disc wear tester.The results show that the NiCoCrAlY-B_(4)C coatings with different B_(4)C mass fractions are mainly composed of NiTi,NiTi_(2),α-Ti,CoO,AlB_(2),TiC,TiB and TiB_(2)phases.The COFs and wear rates of NiCoCrAlY-B_(4)C coatings decrease with the increase of B_(4)C content,which are contributed to the improvement of coating hardness by the B_(4)C addition.The wear mechanisms of NiCoCrAlY-B_(4)C coatings are changed from adhesive wear and oxidation wear to fatigue wear with the increase of B_(4)C content.

Effect of N-ion implantation and diamond-like carbon coating on fretting wear behaviors of Ti6Al7Nb in artificial saliva

The tribology behaviors of Ti6Al7Nb,its alloy with N-ion implantation,and its alloy with diamond-like carbon(DLC)coating were investigated in artificial saliva.Fretting wear tests of untreated,N-ion implanted and DLC coated Ti6Al7Nb alloys plate against a Si3N4ball were carried out on a reciprocating sliding fretting wear test rig.Based on the analysis of X-ray diffraction,Raman spectroscopy,3-D profiler,SEM morphologies and frictional kinetics behavior analysis,the damage behavior of surface modification layer was discussed in detail.The results indicated that the fretting wear behavior of Ti6Al7Nb alloy with N-ion implantation was increased with the dose increase of the implanted nitrogen ions.Moreover,the DLC-coated Ti6Al7Nb alloy with low ion implantation could improve the fretting wear behavior greatly.In addition,the Ti6Al7Nb with DLC coating had better ncorrosion resistance due to the special compact structure.All results suggested that the Ti6Al7Nb with DLC coating had better wear resistance than that with N-ion implantation in artificial saliva.

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.

Si-Al-Y Co-deposition Coatings Prepared on Ti-Al Alloy for Enhanced High Temperature Oxidation Resistance

Si-Al-Y co-deposition coatings were prepared on Ti-Al alloy by pack cementation processes at 1 050 ℃ for 4 h with different halide activators in the packs for enhancing the high temperature oxidation resistance of Ti-Al alloy. The structure, constituent phases, formation process and oxidation behavior of the coatings were investigated. The experimental results showed that the coatings prepared respectively with NaF and NH_4Cl as activators were composed of a（Ti, X）_5Si_4,（Ti, X）_5Si_3（X represents Nb and Cr）, and TiSi_2 outer layer, a TiAl_2 inner layer and an Al-rich interdiffusion zone. However, the constituent phases changed into TiSi_2 in the outer layer and（Ti, X）_5Si_4 and（Ti, X）_5Si_3 phases were observed in the middle layer of the coating prepared with AlCl_3·6H_2O activator. Among the halide activators studied, the coating prepared with AlCl_3·6H_2O was thicker and denser, which is the only suitable activator for pack Si-Al-Y co-deposition coatings on a Ti-Al alloy. The oxidation results show that the coating can protect the Ti-Al alloy from oxidation at 1000 ℃ in air for at least 80 h. The excellent oxidation resistance of the coating is attributed to the formation of a dense scale mainly consisted of TiO_2, SiO_2 and Al_2O_3.

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.

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.

Preparation of Hydroxyapatite-titanium Dioxide Coating on Ti6Al4V Substrates using Hydrothermal-electrochemical Method

Ti6Al4V substrates were anodized in a 0.5 mol/L H_2SO_4 solution at applied voltages of 90-140 V.A hydroxyapatite-titanium oxide（HA-TiO2）coating was then deposited on the anodized Ti6Al4 V substrates via a hydrothermal-electrochemicalmethod at a constant current.The obtained films and coatings were characterized by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fourier-transform infrared spectrometry.The microstructures of the porous films on the Ti6Al4 V substrates were studied to investigate the effect of the anodizing voltage on the phase and morphology of the HATiO_2 coating.The results indicated that both the phase composition and the morphology of the coatings were significantly influenced by changes in the anodizing voltage.HA-TiO_2 was directly precipitated onto the surface of the substrate when the applied voltage was between 110 and 140 V.The coatings had a gradient structure and the HA exhibited both needle-like and cotton-like structures.The amount of cotton-like HA structures decreased with an increase in voltage from 90 to 120 V,and then increased slightly when the voltage was higher than 120 V.The orientation index of the（002）plane of the coating was at a minimum when the Ti6Al4 V substrate was pretreated at 120 V.

High temperature oxidation behavior of (Ti, Al)N coating deposited by arc ion plating

(Ti, Al)N gradient nano-coating was deposited on the surface of 1Cr11Ni2W2MoV stainless steel by the MTP-8-800 arc ion plating equipment. And the oxidation performance at high temperature for 500h was tested under the condition of the surrounding air temperature 700℃. The test results show that, because of the structural features of the （Ti, Al）N coating, the coating becomes the compact and continuous Al2O3 film, which can protect the basis material effectively in the process of the high temperature oxidizing. The oxidation kinetics of the coating accord with parabolic law.

Development and Oxidation Behavior of Al-Cu-Fe Quasicrystalline Coating on Ti Alloy

An oxidation resistant Al-Cu-Fe quasicrystalline coating was fabricated on substrate of Ti alloy by low pressure plasma spraying (LPPS) method. As-sprayed Al-Cu-Fe coating has a rapidly solidified lamellar microstructure consisting of quasicrystalline phase and crystalline phase. The formation of quasicrystalline coating is related to the annealing. The results from the ox!dat!on experiments showed that Al-Cu-Fe quasicrystalline coating improved the oxidation resistance of Ti-base alloys. During the oxidation period there is no evident spallation of the coating from the substrate. Oxide formed on the surface of Al-Cu-Fe quasicrystalline coating after oxidation consisted of Al2O3. Oxidation occurs Ieading to a change of concentration and phase transformation in the coating surface. Selective oxidation of AI transforms the quasicrystalline phase into the phase.

Influences of substrate temperature on microstructure and corrosion behavior of APS Ni_(50)Ti_(25)Al_(25) inter-metallic coating

In the present investigation, Ni_（50）Ti_（25）Al_（25）（at.%） mechanically alloyed powder is deposited on carbon steel substrate.Before the coating process, the substrate is heated to temperature ranging from room temperature to 400℃. The microstructure, porosity, microhardness, adhesion strength, and corrosion behavior of the coating are investigated at different substrate temperatures. Results show that coating porosity is lower on high temperature surface. Microhardness and adhesion strength of the deposition layer on the substrate without preheating have lower values than with preheating. The polarization test result shows that corrosion performance of the coating is dependent on micro cracks and porosities and the increasing of substrate temperature can improve the quality of coating and corrosion performance.

高频感应辅助自蔓延合成TiAl涂层的工艺参数优化

基于Deform建立了高频感应辅助自蔓延合成TiAl系涂层的二维模型,分析了反应前加热过程中基体和压坯的温度分布规律。设计了反应时刻压坯温差最小为实验目标的三因素三水平的工艺参数正交实验。结果表明:影响压坯温差的工艺参数的主次顺序依次为:感应电流、压坯致密度、压头材料。最优工艺参数组合为:感应电流300 A、压坯致密度88.5%、石墨压头。

HiPIMS占空比对Al合金表面Ti/DLC涂层力学和摩擦性能的影响

类金刚石涂层(DLC)兼具高硬度、耐摩擦磨损和高化学惰性等优点,是理想的Al合金零部件耐磨防护材料之一。然而受限于Al合金与DLC间力学性能差异大,摩擦工况下承受复杂的耦合载荷作用,易导致涂层剥落失效。通过改变高功率脉冲磁控溅射技术(HiPIMS)的电源占空比(2%~10%),设计具有不同结构的Ti过渡层,系统研究Al合金基体上不同过渡层界面结构对DLC力学及摩擦性能的影响。结果表明,随HiPIMS占空比增加,所有Ti过渡层取向从(100)向(002)转变。相比直流磁控溅射Ti过渡层,HiPiMS技术可以降低晶粒尺寸以及提高Ti层致密性,令Ti过渡层具备更强的承载能力,涂层摩擦寿命提升了约4.5倍。沉积具有低(100)择优取向和致密结构的Ti过渡层是实现Al合金表面高性能Ti/DLC涂层的关键,对解决Al合金零部件表面硬质涂层易剥落失效等问题提供了新思路。

激光熔覆Ti-Al-N复合涂层高温氧化及摩擦磨损性能

采用激光熔覆于TC4合金表面原位合成Ti-Al-N复合涂层,对比研究复合涂层及TC4基体的高温氧化行为及宽温域下的摩擦磨损性能。结果表明:复合涂层在800℃以下生成以TiO_(2)为主的多层膜,在900和1000℃下涂层氧化产物为TiO_(2)和Al_(2)O_(3)的混合氧化层,涂层表现出较好的抗高温氧化性能;由于氧化膜增厚及涂层中分布的Ti_2AlN自润滑相的作用,800℃时涂层摩擦因数降至0.2091,磨损率降至0.025×10^(-4)mm^3·N^(-1)·m^(-1)是TC4钛合金基体的1.43%。复合涂层在测试温度区间以磨粒磨损为主,高温条件下氧化物具有明显的润滑作用。

Compositing Soft Coated Ti-Fiber Reinforced Ti-Al Matrix Composites

It is showed that there are Ti 3Al, Ti 2Cu and β phase in the interface of Ti/Ti Al composites reinforced with Y 2O 3 Cr composite soft coated Ti fiber, and that interface bonding is intact. Bending strength of the composites can be increased by 26%, to 709 MPa, and bending deflection increased slightly compared with the Ti/Ti Al composites reinforced by Ti fibers coated with Y 2O 3.

铀表面Ti/Al复合镀层在腐蚀气体中的腐蚀行为

研究了铀表面磁控溅射离子镀Ti/Al复合镀层在200～500℃温度范围,分别在0.05MPa的O2、H2O和HCl气体中的腐蚀失效形式。采用俄歇电子能谱(AES)分析了腐蚀后腐蚀介质元素在复合镀层中的深度分布,并采用有限元分析方法计算了在腐蚀加热和冷却过程中复合镀层的应力变化。结果表明:O2、H2O、HCl引起铀表面Ti/Al复合镀层的反应腐蚀温度依次降低,界面分离是Ti/Al复合镀层抗气体加热腐蚀的主要失效形式,Al/U和Ti/Al界面分别成为Ti/Al复合镀层在含O气氛和HCl气体中加热腐蚀的薄弱环节;镀层从界面剥离主要是腐蚀气体从镀层缺陷渗透到界面,降低界面的结合力,从而产生应力引起的。

Al含量对(Ti,Al)N涂层结构性能的影响

(Ti,Al)N是20世纪80年代未期在TiN基础上发展起来的一种新型多元涂层材料。由于加入Al元素,(Ti,Al)N不但硬度、耐磨性优于TiN,而且大大改善了涂层的抗高温氧化性能。综述了Al元素在(Ti,Al)N涂层中的作用机理,以及Al含量对(Ti,Al)N涂层的晶体结构、抗高温氧化、硬度和耐磨性的影响。指出当Ti和Al的比例近似为1:1时,(Ti,Al)N涂层将获得优越的综合使用性能。