原位合成Ti(CN)/Fe复合涂层及耐磨耐蚀性能

采用反应氮弧熔覆技术在Q235A钢试件表面原位合成了Ti(CN)/Fe金属陶瓷复合涂层。利用扫描电镜、XRD射线衍射仪、显微硬度计、摩擦磨损试验机、电化学工作站分析了涂层形貌、涂层物相、涂层显微硬度及其耐磨耐蚀性能,并与Q235A钢进行了硬度、耐磨耐蚀对比试验。结果表明:涂层主要由Ti(CN)、Fe及少量的TiO2相组成,Ti(CN)呈细小颗粒状,涂层为良好的冶金结合;与Q235A钢相比,硬度提高了约3倍,摩擦系数约为Q235A的2/3,磨损量约为Q235A的1/2;在5%H2SO4溶液中,Ti(CN)涂层的腐蚀速率约为Q235A的1/3,在3.5%NaCl溶液中,Ti(CN)涂层的腐蚀速率约为Q235A钢的1/4。     

离子镀TiN/Ti(CN)多层涂层的力学性能与切削性能

采用多层结构的方法可以提高TiN刀具涂层力学性能和切削性能.采用离子镀技术制备了TiN(0.5μm)/Ti(CN)(0.5μm)/TiN(0.5μm)多层涂层.利用光学显微镜、原子力显微镜和微力学探针表征了涂层的微结构和力学性能,并研究了涂层对硬质合金铣刀切削性能的影响.结果表明,TiN/Ti(CN)多层涂层表面平整、厚度均匀、与基底结合良好,硬度为28.5GPa.高速干式切削试验表明,与普通硬质合金铣刀相比,涂层铣刀的使用寿命提高5倍.     

金属有机物PCVD法沉积Ti(CN)涂层

应用PCVD技术,以金属有机物TPT作钛源在H13模具钢表面沉积Ti(CN)涂层,研究了不同工艺参数对涂层组织和性能的影响,并对涂层的抗氧化性进行了实验.结果表明,采用适当的沉积温度、压力及氮气流量,可以在H13钢表面得到以Ti(CN)为主的致密涂层,在沉积温度500℃时达到最高硬度HV1760,涂层在600℃以下具有良好的抗氧化性.     

纳米Ti(CN)基金属陶瓷烧结过程中的结构和相变

用分段真空烧结、X射线衍射和背散射扫描电镜研究了纳米Ti(CN)基金属陶瓷在烧结过程中的结构和相成分的演变.结果表明:纳米Ti(CN)基金属陶瓷在900℃以后,Mo2C和TaC开始由于扩散,与Ti(CN)发生固溶反应,在1200℃以前,Mo2C和TaC固溶反应结束,两相均消失.WC在1100℃以后,开始由于扩散,与Ti(CN)发生固溶反应,在1250℃以前消失.在1250℃以后,合金中只有Ti(CN)和Ni(Ni+Co)两相存在.纳米Ti(CN)粉末与M(M=Mo,W,Ta)反应形成富M的(Ti,M)(CN)固溶体为核,贫M的(Ti,M)(CN)固溶体为环的"亮芯黑环"环形结构,在1350℃即可获得致密的合金.     

Ti(CN)和V(CN)细化剂对工业纯铝晶粒细化效果的对比

采用自制的Ti(CN)和V(CN)粉体晶粒细化剂,研究了其对工业纯铝的晶粒细化能力,提出了其细化机理。结果表明,Ti(CN)和V(CN)粉体晶粒细化剂对工业纯铝有明显的细化效果,且V(CN)的细化能力比Ti(CN)的更强一些。     

钛合金表面反应电火花沉积Ti(CN)涂层研究

利用自行研制的反应电火花沉积系统,以石墨为电极,以工业氮气为保护气,在TCA钛合金基体上原位反应合成了Ti(CN)金属基陶瓷复合涂层.利用SEM分析了涂层单沉积点表面形貌和组织结构,利用X射线仪测定了涂层的物相组成,利用XPS分析了涂层表面元素组成,利用SEM和AES分析了涂层断面形貌、结合状态和元素组成;结果表明,涂层表面单沉积点形貌呈不规则的"溅射状",涂层主要由呈球块状晶和枝晶的TiC0.51N0.12相、Ti080V0.20 相和C相组成且晶块平均尺寸为626nm,涂层与基体的结合致密,呈冶金结合.     

(Ti,V)CN在高碳钢中的应变诱导析出SCIEI

本文研究了V,Ti的碳氮化物在高碳钢中的析出特征。结果表明,PD_3钢在奥氏体区热机械处理时析出相为(Ti,V)CN;增大变形量或降低变形温度使(Ti,V)CN析出颗粒的平均尺寸变小,反之变大;在920℃下(Ti,V)CN颗粒长大过程受界面反应过程所控制。     

不锈钢316L氮化/(Cr,Ti)N涂层原位复合制备

目的研究不同复合涂层的结构及其对力学性能的影响。方法采用等离子体增强磁控溅射系统在奥氏体不锈钢表面分别进行等离子体氮化、(Cr,Ti)N涂层、氮化+(Cr,Ti)N涂层、氮化+Cr+(Cr,Ti)N涂层四种复合表面强化处理。采用XRD、SEM、纳米压痕仪、摩擦磨损仪和划痕仪等分别研究了不同改性层对微观结构以及力学性能的影响。结果氮化后,形成了较高含氮量的过饱和固溶体相(γN),并伴有少量Cr_2N和Fe_2N析出,硬度及杨氏模量分别为18.3 GPa、264.7 GPa。氮化后原位沉积涂层有效避免了氮化物相的析出,过饱和氮原子向基体进一步扩散,增加了氮化层的深度。两种氮化后复合(Cr,Ti)N涂层的硬度和模量均高于单一的(Cr,Ti)N涂层(分别为20.2GPa和271.8GPa),其中氮化+(Cr,Ti)N涂层的硬度和模量均最高(分别为25.4 GPa和345.6 GPa),氮化+Cr+(Cr,Ti)N涂层次之(22.4 GPa和326.3 GPa)。由于氮化层起到了良好的梯度过渡作用,氮化+(Cr,Ti)N涂层的膜基结合力最高,从单一涂层的9.5 N提高到50.9 N,其摩擦系数降低到0.43,磨损量最低,仅为基体的0.66%。结论氮化+(Cr,Ti)N复合涂层的力学性能最佳。     

纳米Ti(CN)基金属陶瓷烧结过程中的组织结构演变

用分段真空烧结、背散射扫描电镜、透射电镜和能谱分析等手段研究纳米Ti(CN)基金属陶瓷在烧结过程中的组织结构演变。结果表明:纳米Ti(CN)粉末金属陶瓷在1 200℃以后开始发生剧烈的固相反应,纳米Ti(CN)粉末与M反应形成富M(M=Mo,W,Ta)的(Ti,M)(CN)固溶体为核,贫M的(Ti,M)(CN)固溶体为环的“亮芯黑环结构”,在1 350℃即可获得致密的合金。而微米金属陶瓷中Ti(CN)粉末颗粒很少参与固溶反应而成为核,富钨和富Mo的固溶体为环,形成“黑芯亮环结构”,烧结温度在1 400℃以上才能获得致密合金。     

纳米晶Ti(CN)基金属陶瓷的研究

对纳米晶Ti(CN)基金属陶瓷进行了初步的研究;与较粗Ti(CN)基金属陶瓷相比,纳米Ti(CN)基金属陶瓷表现更加均匀的球形结构;由于细化的结构和强化的粘结相,纳米结构金属陶瓷具有不同的韧化机理,其断裂韧性要比微米金属陶瓷提高50%。     

RESIDUAL STRESS AND DAMAGE MODE OF HARD Ti(CN)COATINGS

Using free bending method,the residual stress of the Ti(CN)coating on alloy Nb-752 wasmeasured to be 2-3 GPa of which the thermal stress cmounts to 10—20%.An analysis oncoating/substrate interface stress state shows that the share stress at it is about O.1—0.2GPa.The demage mode of the coating under external loading was proposed in terms of theamount and the direction of loading.     

Direct measurement of strain behavior of compression loaded plasma-sprayed yttria-stabilized zirconia

Direct measurement of the stress-strain behavior of stand-alone plasma-sprayed 7 wt.% Y₂O₃-ZrO₂ (YSZ) coatings was made at room temperature. YSZ coatings were evaluated in the as-sprayed condition, and after heat-treatments for 10, 50, and 100 h at 1200 °C using both monotonic and two different cyclic uniaxial compression loading profiles. Heat-treatments were used to change the primarily mechanically interlocked system of lamella to a chemical interlocked system. Monotonic loading of the coatings indicated three different moduli. The first modulus was lower (~ 10 GPa) than observed typically in a plasma sprayed coating. The relatively easy deformation associated with the low modulus was attributed to minor sample crushing near its ends. The second modulus observed was ~ 24 GPa and is due to closure of cracks oriented perpendicular to the stress and lamella sliding and compaction. The third modulus measured ranged from 40 to 48 GPa and represents the elasticity of the material after the easy crack closure and lamella sliding events have occurred. In repeated cyclic loading to a compressive stress of 60 MPa, the coatings were observed to demonstrate large amounts of non-recoverable strain during the first several load/unload cycles, presumably due to permanent sliding and compaction of lamella. Permanent strain tended to a minimum amount after ~ 20 load/unload cycles. Increased cyclic loading from 20 to 320 MPa in 20 MPa increments revealed significant anelastic behavior as evidenced by stress-strain hysteresis loops, particularly in the as-sprayed coating. The elastic moduli of the coatings upon reloading were observed to increase after each subsequent 20 MPa increase in stress applied to the coating to values as high as ~ 80 GPa. This was attributed to an increase in the volume fraction of coating sustaining the load. The amount of non-recoverable strain was highest in the heat-treated coatings indicating a loss of strain tolerance of YSZ coatings during simulated service conditions.     

Residual stress distribution in different depths of TiNi/Ti2Ni-based laser clad coating prepared at different environmental temperatures

This study aimed to effectively reduce the cracking susceptibility of the laser clad coating by enhancing the environmental temperature during laser cladding, and reveal the residual stress distribution in different depths of the coating. The TiNi/Ti₂Ni-based coatings were prepared on Ti6Al4V by laser cladding at different environmental temperatures of 25, 400, 600 and 800 °C. The changes in residual stress along the depth of the coatings were investigated in detail by the nanoindentation method. Results showed that the average residual stress of 2.90 GPa in the coating prepared at 25 °C was largest. With the increase in environmental temperature, the average residual stress was reduced to 1.34 GPa (400 °C), 0.70 GPa (600 °C) and 0 GPa (800 °C). For all the coatings, the residual stress was increased with increasing the distance from the coating surface. Enhancing the environmental temperature can effectively reduce the cracking susceptibility of the coatings.     

Young’s modulus and fatigue behavior of plasma-sprayed alumina coatings

The fatigue behavior and Young’s modulus of plasma-sprayed gray alumina on low-carbon steel substrates were investigated. The investigation of the properties of composites that were defined as “coating-substrate” composites included measurements of the microhardness profile, the residual stress on the top of the coating, and the residual stress profile in the substrate. Fatigue samples were periodically loaded as a cantilever beam on a special testing machine. Failed samples were observed with a scanning electron microscope to determine the failure processes in the coating. The Young’s modulus of the coating was measured by the four-point bending method. Samples were tested both in tension and compression under low (300 N) and high (800 N) loads. The authors’ experiments revealed that the average fatigue lives of coated specimens were nearly two times longer than those of the uncoated specimens. The measurements of Young’s modulus of the coating yielded values that varied between 27 and 53 GPa, with an average value of 43 GPa. Loading in tension caused a decrease in the Young’s modulus of the coating, while loading in compression led to an increase in Young’s modulus. The increase in the lifetime of coated samples was likely due to compressive residual stresses in the substrate, originating during the spray process. The failure of the coating was due to several processes, among which the most important were splat cracking, splat debonding, and the coalescence of cracks through the voids in the coating.     

压裂管柱中陶粒对滑套球座影响

目的：防止陶粒对滑套球座产生破坏。方法利用有限元软件 LS-DYNA 对陶粒冲击滑套球座进行建模,分别改变陶粒与滑套球座表面涂层之间的摩擦系数、滑套球座涂层的厚度、陶粒的粒径、陶粒的速度和陶粒速度相对于滑套球座表面的角度,通过仿真结果观察参数变化对滑套球座表面应力的影响。结果随着陶粒和球座之间的静摩擦系数由0.1增加到0.4,球座的最大表面应力由1.67 GPa增加到2.33 GPa。随着球座表面涂层厚度由3μm增大到6μm,球座的最大表面应力由2.05 GPa减小到0.89 GPa。随着陶粒粒径由50μm增加到80μm,球座的最大表面应力由1.67 GPa增加到3.63 GPa。随着陶粒速度由24 m/s增加到96 m/s,球座的最大表面应力由0.96 GPa增加到2.42 GPa。随着陶粒和球座表面之间的夹角由15°增加到60°,球座的最大表面应力由1.67 GPa增加到4.12 GPa。结论压裂液的性能会影响陶粒和球座之间的摩擦系数,进而影响球座的表面应力大小。球座的表面涂层厚度适当增大可以降低其表面的最大应力,压裂液中陶粒的直径越大,单个陶粒对球座造成的冲击应力越大。可以通过设计使滑套球座表面与中心线的夹角尽量小,以减小球座的最大表面应力。施工排量的增大会加剧球座的破坏。     

直流基体偏压对Al-Cr-Si-N涂层结构和力学性能的影响

采用电弧离子镀技术在不同直流偏压下沉积Al-Cr-Si-N涂层,研究基体偏压对涂层成分、微观结构和性能的影响。结果表明:Al-Cr-Si-N涂层以密排六方结构和面心立方结构的AlN相为主,随着基体负偏压增加,涂层的衍射峰整体向小角度方向偏移:涂层内残余压应力逐渐增加,最大值为-0.77 GPa;涂层硬度和摩擦系数变化不明显。当基体负偏压为-40V时,Al-Cr-Si-N涂层的特征参数H/E和H~3/E~(*2)均达最大值,分别为0.15和0.37GPa,此时涂层具有最佳的耐磨性能,摩擦系数亦最低。     

Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions

Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser-simulated engine heat flux tests. For a 0.25 mm thick ZrO₂-8% Y₂O₃ coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m K to 1.15, 1.19, and 1.5 W/m K after 30 h of testing at surface temperatures of 990, 1100, and 1320 °C, respectively, Hardness and elastic modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and microindentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface and to 7.5 GPa at the ceramic coating surface after 120 h of testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced microporosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various TBC applications.     

用双面氧化弯曲方法测定Al2O3膜生长应力

提出了一种测定氧化膜生长应力的双面氧化弯曲方法,经不象常规弯曲法那样为防止试样一个侧在发生氧化度制保护除层,因而可用于较高温度及较长时间的氧化情况并可测定Ａｌ２Ｏ３膜的生长应力,由于高温下合金及薄氧化膜发生蠕变,从而释放膜内应力。新方法应用于合金的蠕变数据,并采用数值计算来获得氧化膜应力值,用这种方法测定Ｆｅｃｒａｌｌｏｙ（Ｆｅ－２２Ｃｒ－５Ａｌ－０．３Ｙ）合金在１０００℃空气中氧化中形成的Ａｌ２     

激光熔覆FeCoCrNiNb高熵合金涂层组织及力学性能

采用激光熔覆技术在304不锈钢表面制备了FeCoCrNi、FeCoCrNiNb等摩尔比高熵合金熔覆层,研究了Nb元素对熔覆层组织及性能的影响。采用XRD、SEM、EDS、纳米压痕测试和干滑动摩擦磨损实验等方法,详细分析了2种高熵合金熔覆层的相组成、组织演变、纳米硬度及耐磨性能。结果表明：FeCoCrNiNb高熵合金熔覆层相组成为fcc固溶体及富Nb-Laves相。FeCoCrNiNb熔覆层的纳米硬度(H)、弹性模量(E)、H/E和H³/E²分别为6.066 GPa、231.54 GPa、0.0262和0.0042,远高于FeCoCr Ni熔覆层的3.456 GPa、209.48 GPa、0.0165和0.000 94。随着纳米硬度的增加,FeCoCrNiNb熔覆层的摩擦系数和比磨损率也随之降低,分别为0.519和2.54×10^-6mm³/(N·m)。综上所述,FeCoCrNiNb高熵合金熔覆层具有良好的纳米硬度和耐磨性。     

交变和对钢表面有机涂层阴极剥离行为的影响

对１６Ｍｎ钢与ＣＣＳＢ钢表面环氧沥青基有机涂导以常幅交变应力与腐蚀介质共同作用下的阴极剥离行为进行了研究。结果表明,在没有外加应力条件下,涂层具有良好的界面粘附性;而在交变截荷作用的条件下,应力与局部应变集中通过影响有机涂层的介质传输与界面状态,机涂层在介质中的阴极剥离抗力显著降低,降低幅度随外加应力水平面升高。